18. Diagnosis, prognosis & therapy of hepatocellular carcinoma

Ulrich Spengler

Classification of HCC

Tumours are classified to stratify patients with respect to their survival prognosis, in order to select and offer optimised therapeutic options at any tumour stage. For hepatocellular carcinoma (HCC) the Barcelona Clinic Liver Cancer (BCLC) classification has been adopted as the international standard, which is recommended by both the American Association for the Study of Liver Diseases (AASLD) and the European Association for the Study of the Liver (EASL) (Table 1). The BCLC classification takes into account several aspects of the disease: the patient’s general state of health, the severity of the liver disease as well as the extent of tumour spread (Llovet 1999). Patients in stages BCLC O and A have a considerably better prognosis than patients in advanced stages of liver cancer (Mazzaferro 1996). But roughly only 25% of patients with liver cancer are diagnosed at an early stage. Both EASL (EASL 2012) and AASLD guidelines provide recommendations regarding which therapy is best suited to treat patients at each stage of the BCLC classification. Unlike classification schemes in other types of malignancies, the BCLC classification is particularly helpful because it is entirely based on clinical parameters – molecular characteristics are not yet able to reliably assess individual prognosis of patients with HCC.

The BCLC classification seems to assess prognosis less accurately in Asian patients, where hepatitis B is a prevailing cause of liver cancer. An alternative classification, the Hong Kong Liver Cancer Staging System (HKLC), has been proposed recently, which had significantly better ability in Asian patients to distinguish subgroups with specific overall survival times (Yau 2014). Importantly HKLC identified subsets of patients with intermediate and advanced stages of liver cancer, who might benefit from more aggressive therapy (resection in intermediate stage, chemoembolisation in advanced stage). Nevertheless thus far, the HKLC classification is based exclusively on retrospective data from Asian patients in a single centre and still awaits confirmation by prospectively controlled studies and in non-Asian patients.

The Cancer of the Liver Italian Program (CLIP) has derived another widely used prognostic tool for HCC. The CLIP score combines features of macroscopic tumour morphology (unimodular versus multimodular with limited extension < 50% versus massive with extension > 50%), serum alpha-fetoprotein (AFP <400 ng/mL versus > 400 ng/mL), the Child-Pugh stage, and the presence of portal vein thrombosis to determine a prognostic score ranging from 0 -6 (Anonymus 2000). Patients with advanced HCC and low serum levels of vascular endothelial growth factor (VEGF) or high levels of insulin-like growth factor I (IGF-1) have better survival at each disease state than those with serum levels in the opposite range. Thus, VEGF and IGF-1 can been added to the CLIP score as an additional component referred to as V-CLIP or I-CLIP, respectively (Kaseb 2011a and 2011b).

The latest prognostic classification combines serum albumin and bilirubin alone (the ALBI score) and provides an easy-to-use, objective and discriminatory method for assessing liver functions in patients with HCC. Its validity has been confirmed in geographically distinct cohorts of patients with HCC either undergoing liver surgery for localised disease and sorafenib treatment for advanced disease (Johnson 2015).

Epidemiology

HCC constitutes the fifth most frequent form of cancer worldwide, and it holds the second place in malignancy-related mortality (Jemal 2011). Incidence and death rates of HCC are steadily rising in most parts of the world (about 2-3% per year). It occurs two to six times more frequently in men than in women. The key risk for HCC is liver cirrhosis, approximately 80% of which are related to hepatitis B and C on a global scale.

Chronic hepatitis B is the major risk factor for developing HCC in Africa and Asia, while in the US, Europe and Japan chronic hepatitis C, alcohol and non-alcoholic steatohepatitis (NASH) are leading causes of HCC. Eighty percent of liver cancers are found in cirrhotic livers, which themselves carry a high risk for HCC. Chronic carriers of hepatitis B virus (HBV) have a 100-fold increased risk as compared to a non-infected healthy reference population. Recent reports from Taiwan indicate a direct link between HBV viral loads and the risk of developing liver cancer within 10 years (Chen 2006, Iloeje 2006). The risk of HCC is significantly increased once HBV-DNA exceeds 2000 IU/mL irrespective of the degree of hepatic inflammation. Quantitative HBsAg ≥1000 IU/mL is a further biomarker of increased HCC risk in patients with low or intermediate levels of HBV-DNA (Tseng 2013). The risk to develop HCC is higher in infection with HBV genotype C than B and also in infection with genotype D than A. Co-infection with HCV and HDV and/or exposure to environmental toxins such as aflatoxins and the algal toxin microcystin in drinking water further increase the risk of HCC.

Approximately 70 million people are infected with the hepatitis C virus worldwide, 20 to 30% of whom will develop liver cirrhosis, which carries a 3-5% annual risk of ultimately progressing to liver cancer. Unlike hepatitis B, a close relationship between HCV-RNA and the risk of developing HCC apparently does not exist (Bralet 2000). As a general rule patients will not develop liver cancer in chronic hepatitis C before their disease has progressed to advanced fibrosis and cirrhosis (Lok 2009). It appears that the risk of HCV-induced HCC related to the degree of inflammation and necrosis, while HBV-related HCC does not correlate well with inflammation and seems rather to involve activation of specific oncogenes by the virus.

Consumption of alcohol or tobacco enhances the risk of HCC (Donato 2002, Gelatti 2005). Beyond that, obesity (Calle 2003) and diabetes mellitus (Davila 2005) must be considered pivotal risk factors that can independently lead to liver cancer in Western countries and result in 4- to 40-fold increased HCC rates among patients with chronic viral hepatitis (Starley 2010). In patients with steatohepatitis, liver cancer can occur before cirrhosis has developed. Importantly, the risk of HCC is substantially reduced in diabetic patients who are treated with metformin (Lai 2012).

Finally, certain heriditary diseases such as haemochromatosis and alpha1-antitrypsin deficiency predispose to HCC. Also genetic polymorphisms in the adiponutrin gene (rs 738409 C>G), in the KIF1B gene (rs 17401966), and the MICA gene (rs 2596542) seem to predispose patients with alcoholic and non-alcoholic fatty liver disease, chronic HBV and HCV infection, respectively, to develop cirrhosis and HCC (Fallet 2011, Nischalke 2011, Trepo 2013, Zhang 2010, Kumar 2011).

Surveillance of patients at high risk and early HCC diagnosis

Surveillance is cost effective if the expected HCC risk exceeds 1.5% per year in hepatitis C and 0.2% per year in hepatitis B. Simple clinical scores have been developed in hepatitis B (e.g., the REACH-B score) and hepatitis C (e.g., the HALT-C score) to assess when HCC surveillance becomes cost-effective (Chen 2013, Yuen 2009, Lok 2009). Surveillance has to be based on ultrasound examination at 6-month intervals. When 3- versus 6-month surveillance intervals were compared in a randomised study involving 1200 patients, there was no evidence that the shorter interval improved rates of early diagnosis and therapeutic outcomes. However, if patients with cirrhosis harbor nodular lesions, the 3-monthly control interval is preferred due to the high potential of malignancy and growth characteristics of such lesions (Yao 2006). Thus, nodules <1 cm, which usually are not HCC, should be monitored in 3-4 month intervals until they are proven to be stable or disappear (for up to 24 months). Nodules >1 cm should be evaluated with either 4-phase computed tomography (CT) or dynamic contrast-enhanced magnetic resonance imaging (MRI) as outlined in the section on diagnosis. Alpha-fetoprotein (AFP) has insufficient sensitivity and specificity, and thus is no longer recommended for HCC surveillance. Des-gamma-carboxy prothrombin (DCP), glycosylated AFP (AFP-L3), and glypican-3 are being evaluated with respect to HCC surveillance,  and integrated as components of the GALAD score have outperformed ultrasound in a recent study suggesting that their combination with ultrasound might result in improved HCC surveillance of high risk patients (Yang 2019). The consistent use of ultrasound in patients with high risk for HCC enables us to diagnose carcinoma early in 30% of patients who then have a reasonable chance of curative therapy. On the other hand, Caucasian patients with low or no HBV activity are at low-risk for HCC, and surveillance is generally not recommended in such patients.

Diagnosis

Patients who develop HCC usually have no symptoms other than those related to the underlying chronic liver disease. However, in patients with sudden hepatic decompensation such as ascites, jaundice, hepatic encephalopathy or variceal bleeding often caused by portal vein thrombosis there is an increased likelihood of HCC. Occasionally patients develop paraneoplastic syndromes (hypoglycaemia, erythrocytosis, hypercalcaemia, severe watery diarrhoea, dermatomyositis and various types of skin lesions), which apart from erythrocytosis herald a poor prognosis (Luo 2002). Plasma micro-RNAs are currently under evaluation as biomarkers for the non-invasive diagnosis of HCC at any stage (Borel 2012).

The diagnosis of HCC is made by detecting malignantly transformed hepatocytes in a liver biopsy or by dynamic contrast-enhanced radiological imaging techniques demonstrating intense arterial uptake followed by wash-out of contrast in the delayed venous phases reflecting arterialised perfusion of the tumour. Contrast-enhanced ultrasound may falsely suggest HCC in some patients with cholangiocarcinoma, and it should not be used as the only diagnostic tool for HCC (Vilana 2010). Nevertheless, novel diagnostic algorithms enable the diagnosis of HCC in a cirrhotic liver without histopathology or reference to elevated tumour markers.

The revised WHO classification distinguishes new specific subtypes of hepatocellular carcinoma (steatohepatitic, clear cell type, macrotrabecular massive, chromophobe fibrolamellar, scirrous, neutrophil-rich, lymphocyte-rich (WHO 2019). In particular the distinction between a dysplastic nodule and early HCC poses a particular challenge for the pathologist. Staining for glypican-3, heat shock protein 70, and glutamine synthetase is advised in this situation, and positivity for any two of these three markers confirms the presence of HCC (International Working Party 2009). Differentiation of HCC from cholangiocarcinoma may also require cell-type specific markers such as keratin-7, keratin-19, or CA 19-9.

Radiological diagnosis of HCC uses detection of hyper-vascularised nodular lesions. Contrast-enhanced computed tomography (CT) or nuclear magnetic spin resonance tomography (MRI) are considered to be equivalent diagnostic tools, and international consensus guidelines accept a diagnosis of HCC without histopathology, if the patient with a nodular lesion in a cirrhotic liver exhibits the following sequence of events: in the arterial phase, HCC enhances more intensely than the surrounding liver, because arterial blood in the liver is diluted by venous blood from the portal venous circulation, whereas HCC contains only arterial blood. In the venous phase, HCC enhances less than the liver, reflecting the fact that HCC does not have a portal venous blood supply and that the arterial blood flowing into the lesion no longer contains contrast. This phenomenon is termed “washout”. In the delayed phase “washout” persists, and occasionally HCC can only be detected in this phase of a dynamic study. Thus, a four-phase dynamic study is needed to reliably make a diagnosis of HCC (unenhanced, arterial, venous and delayed venous phases). Contrast enhancement in the early arterial phase, which disappears in the late venous phase, is highly specific for HCC.

Diffusion-weighted imaging (DWI) in MRI reflects water mobility in tissues, which is impeded in HCC tissue. Thus HCC results in signal hyperintensity within the tumour relative to the liver parenchyma. A recent meta-analysis provided evidence that DWI combined with dynamic contrast-enhanced MRI performed significantly better than any of the two imaging techniques alone (Wu 2013). Hepatocyte-specific contrast agents such as gadoxate disodium and gadobenate dimeglumine are taken up by normal hepatocytes. Since most HCCs do not contain functional hepatocytes, signal hypointensity relative to the surrounding liver is observed in the hepatobiliary phase. As a consequence, hepatobiliary phase images are highly sensitive for HCC. However, this technique has only poor specificity (Bartollozzi 2013). Nodules with a hypointense signal in the hepatobiliary phase but without diagnostic features of HCC in the other phases may represent highly dysplastic nodules or early HCC and carry a high risk of progressing to conventional hypervascular HCC.

The current recommendations for diagnosis of HCC are summarised in Figure 1. For lesions smaller than 1 cm, detailed investigation is not recommended because most lesions will represent regenerative nodules rather than HCC. However, close follow-up in 3-month intervals should be offered using the same imaging technique that detected the lesion in the first place.

For lesions larger than 1 cm, a guided biopsy of the lesion should be performed because diagnostic accuracy of radiological procedures declines with smaller liver tumours, while high (>90%) diagnostic sensitivity and specificity is maintained by histological analysis of biopsy specimens (Serste 2012). Alternatively, either dynamic MRI or multidetector CT scans can be performed. If radiological findings are characteristic for HCC as described above, a firm diagnosis of HCC can be made and no further steps are necessary.

Contrast-enhanced CT and MRI exhibit excellent diagnostic sensitivity and specificity if the rules regarding early hypervascularity and washout are strictly applied. The presence of arterial hypervascularisation alone is not sufficient for a diagnosis of HCC, which requires the presence of venous washout as an essential second diagnostic component. In equivocal situations the diagnosis must be clarified by biopsies, which may have to be repeated within a short period of time.

Radiological assessment of treatment responses should not be based on tumour size alone but apply modified Response Evaluation Criteria in Solid Tumours (mRECIST) (Lencioni 2010). High quality arterial-phase imaging is required for this purpose. In general, MRI is preferred over CT owing to its superior tissue contrast resolution and sensitivity to detect both the tumour and post-treatment changes. Using contrast-enhanced techniques, absence of uptake within the tumour is considered to reflect necrosis, while persisting uptake indicates vital tumourous tissue. Rim contrast enhancement after ablative loco-regional therapy is not indicative of viable tumour, unless contrast enhancement also reveals nodular or thick uptake along the tumour margins or a clear wash-out (Chung 2012, Riaz 2009). Tumour recurrence is signaled by the re-appearance of vascular enhancement.

Stage-adapted therapy for liver cancer

The two key factors that are most important in determining a patient’s prognosis and potential treatment options are the tumour mass and hepatic functional reserve. Patients with early HCC have excellent chances for curative cancer treatment. They can achieve 5-year survival rates of 50-70% by surgical resection, liver transplantation or percutaneous ablative procedures. With more advanced HCC, local transarterial embolisation and multikinase inhibitor therapy can still prolong life. Figure 2 gives a summary and concise overview of stage-adapted therapy for hepatocellular carcinoma.

Potentially curative therapy in BCLC stages 0-A

Surgical resectionconstitutes the backbone of curative treatment in patients with early HCC. It is the treatment of choice in patients with localised tumour spread and small-sized cancers and tumours in a non-cirrhotic liver (evidence grade IIIA). Prognosis after surgical resection is excellent, if the tumour is not larger than 2 cm in diameter (5-year survival rates 70-90% with rates of tumour recurrence below 10%). Excluding patients with poor liver function keeps perioperative mortality below 5%. Favourable criteria for surgical resection comprise single nodules less than 5 cm in size or a maximum of 3 nodules in a single liver lobe. Patients should be carefully selected to diminish the risk of postoperative liver failure. Patients should have only moderately impaired liver function (Child’s stage A cirrhosis), should not have portal hypertension (hepatic-portal-vein pressure gradient >10 mm Hg, presence of oesophageal varices or splenomegaly together with reduced platelet counts <100,000/µl) and should have a serum bilirubin in the normal range. Patients with tumour invasion of a major portal or hepatic vein, direct invasion of neighboring organs other than the gallbladder, peritoneal disease, and nodal or distant secondaries are not candidates for surgery.

Potentially curative partial hepatectomy is the optimal treatment for HCC in patients with adequate hepatic functional reserve. Right hemi-hepatectomy in cirrhotic patients has a higher risk of inducing hepatic decompensation than left hemi-hepatectomy. Non-anatomic resection may be necessary to minimise loss of functional liver parenchyma. Operative mortality for HCC is related to the severity of liver disease, and patients with complications of cirrhosis such as marked portal hypertension, ascites or bleeding have insufficient hepatic reserve to withstand resection. Most deaths are due to postoperative liver failure and < 10% are related to complications of bleeding. Ninety-day mortality rates appear a more reliable indicator of outcomes than 30-day perioperative mortality, especially in patients with extended resections and resections of cirrhotic livers, since progressive jaundice, ascites and eventually death develop slowly and well after 30 days in patients with marginal residual liver function. Of note, common prognostic tools, e.g. the Child-Pugh Classification or the Model for End-stage Liver Disease (MELD) score, are not adaequate to identify patients with insufficient hepatic functional reserve after resection. Volume and function of the residual liver remnant can be determined by hepatic volumetry which is best performed before and after portal vein embolisation. Also CLIP and ALBI scores help to assess the hepatic functional reserve and risk of surgical resection. Because hepatic regeneration is impaired in cirrhosis, resection in general should not exceed 25% of the liver parenchyma. Preoperative portal vein embolisation can be used in selected patients to increase the volume of the liver remnant prior to major liver resections, particularly for right-sided tumours, because it initiates hypertrophy and allows for more extensive resections (Abulkhir 2008, Leung 2014). Selective arterial chemoembolisation (TACE) has been recommended as a complementary procedure prior to portal vein embolisation because it reduces arterial blood supply to the tumour and also embolises potential arterioportal shunts (Yoo 2011).

Liver transplantation is an alternative therapeutic option, if the liver cancer cannot be cured by local resection due to anatomical reasons, if residual liver function after resection is anticipated to be poor, or if there is multi-nodular tumour spread into both liver lobes (grade IIIA evidence). Virtually all patients considered for liver transplantation are unresectable due to the degree of liver dysfunction rather than tumour extent. Commonly, patients with HCC are selected for liver transplantation according to the so-called Milan criteria, i.e., the patient has a single nodule of less than 5 cm in diameter or at most 3 nodules, none of which exceeds 3 cm in diameter (Mazzaferro 1996). Patients who meet the Milan criteria usually achieve survival rates of 80% and 70% one and five years after liver transplantation. However, it has been demonstrated that selected patients with more extensive stages of liver cancer can be transplanted with reasonable long-term outcomes (Yao 2001). Selection of patients according to the San Francisco criteria comprises solitary large nodules up to 6.5 cm as well as multi-nodular HCC with a maximum of 3 nodules, each of which must be smaller than 4.5 cm with a total sum of all nodule diameters less than 8 cm. Patients who remain within these extended selection criteria can still reach 70-80% five-year survival rates after liver transplantation. However, there is very limited data to support extending selection criteria for liver transplantation any further (Pomfret 2010).

A central issue in liver transplantation is the process of fair organ allocation. Shortage of donor organs is particularly critical in patients with liver cancer, because the tumour will continue to expand while the patient is on the waiting list, and can ultimately reach a stage that makes liver transplantation a futile option. It has been estimated that after one year on the waiting list, approximately 40% of patients can no longer be cured by liver transplantation (Poon 2007). In the Eurotransplant registry donor livers are allocated to patients according to their MELD scores. To circumvent the problem that patients with early HCC who are eligible for liver transplantation have rather low MELD scores, Eurotransplant accepts the diagnosis of HCC within the Milan criteria as so-called standard exemption, allocating additional points on top of the patient’s lab MELD score in an incremental time-dependent fashion.

EASL/EORTC guidelines recommend to treat liver cancers locally when the expected time on the waiting list exceeds 6 months (EASL/EORTC 2012). Bridging therapy can be done by transarterial chemoembolisation, radiofrequency ablation or partial resection. This strategy probably also facilitates patient selection for liver transplantation, because those with stable disease after chemoembolisation achieve a greater than 90% five-year survival rate after liver transplantation, while only 35% of patients in the group with progressive tumour expansion survive five years post-liver transplantation (Otto 2006).

Sirolimus, an inhibitor of mammalian target of rapamycin (mTor inhibitor) seems to be a promissing immunosuppressive agent in liver transplantation of HCC, because it has antiproliferative activity against HCC in vitro and in vivo and can interfere with vascular endothelial growth factor (VEGF). Several early reports suggested a lower risk of posttransplant HCC recurrence with the use of sirolimus, and a registry-based comparison of 2491 adult patients with liver cancer, who underwent transplantation, versus 12,167 liver transplantations for other diagnoses suggested a postransplant survival benefit for the use of sirolimus, that was specific to patients transplanted for HCC (Toso 2010). In support, a recent meta-analysis suggested that sirolimus-based regimens significantly decreased overall tumour recurrence rates and recurrence-associated mortality (Menon 2013). Although these data are encouraging, the International Consensus Conference on Liver Transplantation for HCC does not yet generally recommend sirolimus for transplantation in HCC, since available data are entirely derived from retrospective studies (Clavien 2012). Everolimus, a semisynthetic form of sirolimus may have similar effects as sirolimus but has not been studied adaequately in patients with HCC. Side effects of sirolimus comprise thrombosis of the hepatic artery, delayed wound healing, incisional hernias, hyperlipidaemia, bone marrow suppression, mouth ulcers, skin rashes, albuminuria, and pneumonitis. Because of their side effect profile, in particular hepatic artery thrombosis, mTor inhibitors should not be used in the first three months after liver transplantation.

Non-surgical local procedures: Image-guided ablation is recommended for patients with early HCC when surgical options are precluded.

Radiofrequency ablation (RFA) is currently considered the standard technique, because most clinical data are available for RFA: A cohort study on percutaneous radiofrequency ablation demonstrated that complete ablation of lesions smaller than 2 cm is possible in more than 90% of patients with local recurrence in less than 1% (Livraghi 2008). In larger tumours, five-year survival rates are somewhat lower, at 70-80% for nodules less than 3 cm in diameter, and 50% for tumours between 3 and 5 cm (Lopez 2006). A cumulative meta-analysis has suggested that survival is better after radio frequency ablation than after ethanol injection (Cho 2009). In up to a third of patients a self-limited postablation syndrome has been reported after RFA which was associated with fever, malaise, chills, right upper quadrant pain, nausea and elevated liver enzymes (Dodd 2005). RFA is avoided for lesions in the hepatic dome or along the inferior liver edge to avoid diaphragmatic injury or intestinal perforation. In addition to size the local efficacy is also affected by the proximity of a lesion to large blood vessels (Lu 2005), probably because the blood flow carries away heat from the lesions (the “heat sink” phenomenon). Following RFA gas bubbles may form in the liver as a result of treatment and should not be mistaken for infection or infarction (Park 2008). Although RFA is relatively well tolerated, severe and potentially fatal complications can occur, e.g. liver abscess, pleural effusion, pneumothorax and skin burns, subcapsular hepatic hematoma and needle tract seeding of tumour cells (Takaki, 2013). Outcomes of RFA are superior to percutaneous ethanol injection and may be equivalent to surgery in small tumours.

Some alternative treatment modalities have recently attracted attention because they may overcome some of the limitations associated with RFA.

Microwave ablation (MWA) can generate very high temperatures in the tumour tissue in a very short time. This can potentially lead to enhanced treatment efficacy and larger ablation zones and can reduce susceptibility to heat dispersion by blood flow in major vessels (Boutros 2010).

Cryoablation refers to methods, which destroy tissue by local freezing or alternating freezing and thawing. Rapid tissue freezing and thawing produce a cytotoxic effect by disrupting cellular membranes and inducing cell death. The cryolesion is hypechogenic and can be visualised and monitored by intraoperative ultrasound. Cryoablation can lead to equivalent treatment outcomes as RFA (Wang 2015). However, meanwhile most centres have abandoned cryoablation, because other techniques, e.g. RFA are technically easier to do, may potentially be associated with less local recurrence and lower complication rates.

Irreversible electroporation (IRE) induces cell death by repeated application of short-duration high-voltage electrical pulses, which irreversibly injure cellular membranes. Although hyperthermic effects may occur with high power applications, cell death associated with IRE is induced non-thermally. Hence, cooling owing to high perfusion is not a problem with this technique (Scheffer 2014). However, general anesthesia with neuromuscular blockade and cardiac gating to prevent arrhythmias are required. Other energy-based ablation treatment approaches comprise laser induced thermal therapy (LITT) and high-intensity focused ultrasound (HIFU). Efficacy and safety of HIFU for primary or recurrent HCC has been predominantly studied in Hong Kong and appeared similar to outcomes with RFA. However, clinical experience outside of China is rather limited, since only a few centres worldwide have adopted these techniques. Thus, the place of HIFU is currently undefined.

Adjuvant therapy, in the context of resection, liver transplantation or local-ablative procedures, does seem to offer additional benefits. Thus far, antiviral treatment of hepatitis B with nucleos(t)ide analogs remains the single approved treatment after removal or local destruction of HCC. Interestingly, one study (Su 2014) reported that recurrence-free survival and overall survival were significantly better in 9,461 Taiwanese patients who had liver resections for HBV-associated HCC between 1997 and 2011, when they were on anti-platelet therapy.

A randomised phase 3 trial involving 1,114 HCC patients after liver resection or local ablation, who were randomised to receive either sorafenib or placebo for 4 years or until tumour recurrence (STORM trial), did not meet its primary and secondary endpoints of recurrence-free survival, time to recurrence or overall survival (Bruix 2015). Positive reports are available from phase 2 trials with transarterial radioactive 131-iodine, capecitabine, heparanase and thalidomide. However, confirmatory phase 3 data are not yet available for any of these agents.

Tumour recurrence is frequent after putatively curative treatment of HCC. Although there is no generally accepted consensus on posttreatment surveillance, most centres apply CT or MRI imaging every 3 to 6 months for first two years after therapy, then annually, and if initially elevated, also recommend monitoring serum AFP every 3 months for first two years, then every 6 months (Clavien 2012). Most HCC recurrences are intrahepatic and reflect local recurrence or a new second primary lesion (Hatzaras 2014). The best predictors of HCC recurrence are high serum alpha-fetoprotein levels (AFP >500 ng/mL), microvascular invasion and/or additional tumour sites besides the primary lesion. Solitary nodules might be amenable to repeat resection, but HCC recurrence is frequently multifocal owing to intrahepatic dissemination of the tumour. Some patients with HCC recurrence after primary resection might benefit from salvage transplantation. The role of HBV infection for HCC recurrence after resection is under debate (Sun 2007, Cescon 2009, Char 2014), and early HCC recurrence has been reported to be even greater in hepatitis C infected patients than HBV infected patients (Utsunomiya 2015). Therapy with antiviral drugs seems to reduce late (≥ 2 years) HCC recurrence in chronic hepatitis B and C but does not seem to have much effect on early HCC recurrences (Yin 2013, Huang 2015). The effects of direct antiviral therapy in patients with HCV-related HCC is not yet clear, since rapid recurrence and expansion of HCCs have been reported to occur shortly after DAA therapy, even when the primary HCC had been “cured” quite some time before (Conti 2016, Kozbial 2016, Reig 2016).

Palliative therapy in BCLC stages B and C

Palliative treatment remains the only therapeutic option for patients with advanced stages of liver cancer that cannot be controlled by local therapy.

Arterial chemoembolisation is the most frequent palliative intervention offered to patients with HCC and is considered for patients with non-surgical HCC who are also not suited for percutaneous ablation and do not have extrahepatic tumour spread. HCC exhibits intense neoangiogenic activity, so that even well-differentiated HCCs become highly dependent on arterial blood supply. Thus, hepatic arterial obstruction is performed either by angiographic transarterial embolisation or transarterial chemoembolisation. Usually lipiodol combined with an embolising agent such as gelatin or microspheres is mixed with cytostatic drugs and applied to the liver via an intra-arterial catheter. Suitable cytotoxic agents are doxorubicin, mitomycin and cis-platinum, but the optimal combination of drugs and treatment schedules has not been established. In randomised studies demonstrating a benefit of chemoembolisation, doxorubicin or cis-platinum was administered in 3-4 angiographic sessions per year. Chemoembolisation carries the risk of ischemic damage to the liver, potentially leading to fulminant liver failure. To minimise this risk chemoembolisation should be offered only to patients with good residual hepatic function, who have asymptomatic multi-nodular liver cancer without vascular invasion or extrahepatic tumour spread. Vice versa patients with decompensated liver disease (liver cirrhosis, Child’s B or C) or imminent hepatic failure should not undergo chemoembolisation. Table 2 lists absolute and relative contraindications for chemoembolisation.

The side effects of interarterial chemoembolisation are the same as for systemic chemotherapy and consist of nausea, vomiting, bone marrow depression, alopecia and renal damage. TACE is a risk factor for hepatitis B virus reactivation and antiviral prophylaxis is recommended in HBsAg positive patients. Common ischemic complications comprise a hepatic abscess, acute cholecystitis and damage to biliary tracts. Interstitial pneumonitis and gastrointestinal ulcerations due to abnormal shunting may occur owing to radiation injury. Pulmonary or cerebral lipiodol embolisations are rare but potentially fatal complications. Overall, treatment-related mortality rates are about 2%. As a frequent complication of hepatic ischaemia, more than 50% of patients also develop a so-called post-embolisation syndrome with fever, abdominal pain and a moderate degree of ileus. Fasting and fluid replacement is mandatory, but the post-embolisation syndrome is usually self-limited and patients can be discharged safely after 2 days.

Objective response rates vary between 16% and 60%, but less than 2% of patients achieve complete remission. Residual tumour cells recover their blood supply and the tumours continue to grow. Thus, repeated therapy may be needed. However, multiple courses can increase death from liver failure despite good tumour reduction; thus, counterbalancing the potential survival benefits from repeated treatment. TACE should be limited to the minimum number of interventions needed to control tumour growth.

Chemoembolisation is currently considered to significantly improve survival in suitable palliative patients (Llovet 2002). Beyond that, combination therapy with TACE and RFA appears to be the most efficient treatment of early HCC (Lan 2016) and is used as bridging therapy for HCC patients on the waiting list for liver transplantation. However, its use in patients allocated to curative resection it is not recommended, because surgical complication rates are increased thereafter.

DEB TACE (transarterial chemoembolisation using drug eluting beads) constitutes a modification of chemoembolisation, where embolising particles act as carriers and are loaded in vitro with cytotoxic agents such as doxorubicin. In addition to their ischemic effects, drug-eluting beads release the drug into the tumour microenvironment in a slow and controlled fashion, thus potentially enhancing their antitumoural activity. While the clinical response to DEB chemoembolisation is rather similar to conventional chemoembolisation, systemic exposure to chemotherapy is apparently reduced; in particular, biliary side effects are less frequent and left ventricular function better preserved (Vogl 2011). Conversely, treatment-associated gastrointestinal adverse effects appear to be more frequent in DEB-TACE than in conventional chemoembolisation. Meanwhile, also irinotecan-eluting beads are being studied.

Radiotherapy with Yttrium-90 microspheres has been developed as a novel alternative palliative treatment of liver cancer with unexpectedly impressive anti-tumoural activity in selected individual cases (Sangro 2006, Jacobs 2007, Salem 2006, Liu 2004). Very small particles (25 – 45 µm) made of glass (TheraSpheres®) or resin (SIR-Spheres®) serve as sealed sources of the radio-emitting isotope 90-yttrium (90Y). Microspheres are injected during hepatic angiography and ultimately lodge in the abnormal tumour vessels. To avoid misplacement of microspheres into extrahepatic territories a thorough angiographic evaluation comprising injection of 99Tc macro-aggregated albumin is necessary prior to treatment in order to detect and eventually occlude aberrant vessels, and to also assess hepatopulmonary shunting. Of note, unlike chemoembolisation, small microspheres do not occlude the blood vessels and can also be applied in the presence of portal vein thrombosis. Radioembolisation potently induces tumour necrosis. However, the therapeutic response to 90Y-radiotherapy is delayed; the median time to develop necrosis (reduced contrast enhancement) and tumour shrinkage are approximately 30 and 120 days, respectively (Keppke 2007). Furthermore, heterogenous contrast enhancement in a perivascular distribution of a 90Y-treated liver segment or lobe reflects radiation injury and should not be interpreted as tumour progression (Riaz 2009). In a randomised controlled, prospective phase 2 study on 45 HCC patients in BCLC stages A and B, 90Y radioembolisation resulted in significantly longer times to progression than chemoembolisation (>26 months versus 6.8 months, Salem 2016).

Randomised controlled trials comparing radioembolisation to other treatment strategies are not yet available. However there is accumulating good evidence from several well-characterised large cohort studies (Hilgard 2010, Salem 2010, Sangro 2011, Mazzaferro 2013). Taking into account tumour stage, intermediate tumour stage patients treated by radioembolisation achieve 16 to 18 months of median survival time (Salem 2010, Sangro 2011, Mazzaferro 2013). Adverse events, response rates and time to progression appeared improved while overall survival was equivalent when radioembolisation was compared to chemoembolisation (Salem 2011). When downstaging to transplantation is allowed by local regulations, radioembolisation outperforms chemoembolisation (Lewandowski 2009). Finally, a randomised controlled phase 3 trial in 467 patients comparing radioembolisation to sorafenib chemotherapy did not reveal any significant survival difference between the two treatment arms (SIRT: 8.0 months versus sorafenib 9.9 months; p=0.18) (Villain 2017).

Systemic chemotherapy with conventional anti-cancer drugs does not seem to offer survival benefits, whether given as a single agent or as part of combination chemotherapy (Llovet 2003). Likewise, anti-hormonal therapy with tamoxifen or octreotide has not provided improved patient survival when studied under controlled conditions (Gallo 2006, Yuen 2002).

Systemic palliative HCC therapies

Molecular-targeted therapeutic strategies offer new hope for effective palliative therapy in liver cancer. Sorafenib (Nexavar®) is an orally available multi-kinase inhibitor acting on several distinct tyrosine kinases (VEGFR2, PDGFR, c-kit receptor) as well as on serine/threonine kinases (b-Raf and p38). Thus, by inhibiting angiogenesis and cellular proliferation, sorafenib can block two of the major signalling pathways of HCC expansion. In a phase 3 study (the SHARP trial) involving 602 patients, sorafenib 400 mg BID was moderately well-tolerated and associated with improved survival in 44% of patients resulting in 3 months extended survival in treated patients (10.7 months in the sorafenib arm versus 7.9 months in the control arm). The efficacy of sorafenib has been confirmed in a second randomised placebo-controlled trial, mostly involving patients with HBV-associated HCC (Cheng 2009) and in 1586 patients of the GIDEON (Global Investigation of Therapeutic Decisions in Hepatocellular Carcinoma and of its Treatment with Sorafenib) prospective database (Lencioni 2012). Sorafenib has established itself as the first option in patients with HCC who can no longer be treated with  local therapies. The SHARP trial largely included patients with preserved liver function. Although the pharmacologic profile is favourable, data in Child-Pugh class B patients are scarce (Abou Alfa 2011). Patients with liver cirrhosis Child class C, however, do not achieve a survival benefit from sorafenib and should only receive best supportive care. Diarrhea, weight loss, hand-foot syndrome and rash, hypertension, renal toxicity with hypophosphataemia, thromboembolism, bleeding, cardiotoxicity, thyroid dysfunction, pruritus, alopecia, impaired wound healing and hepatotoxicity are important side effects of sorafenib. Sorafenib has also been associated with fulminant hepatic toxicity, which is characterised by elevated aminotransferases, coagulopathy and hyperbilirubinaemia. Sorafenib is apparently particularly effective in HCC related to chronic hepatitis C. However, its role for treatment of recurrent HCC after liver transplantation currently remains still undefined. Sorafenib can be safely combined with chemoembolisation therapy (Pawlik 2011) but this combination apparently does not provide any clinical benefit. Likewise, in the SORAMIC study the combination of sorafenib with 90 Yttrium radiotherapy (SIRT) did not result in better survival than sorafenib alone. However, certain patient subgroups, e.g. young patients, non-cirrhotic patients or those with a non-alcoholic aetiology, may still benefit from a SIRT/sorafenib combination treatment.

Lenvatinib (Lenvima®), is an inhibitor of VEGF receptors 1-3, FGF receptors 1-4, PDGF receptor a, RET and KIT and shows activity in hepatocellular carcinoma. The phase III REFLECT study comparing lenvatinib (8-12mg/d) to sorafenib (400 mg twice daily) in untreated patients with advanced hepatocellular carcinoma revealed that lenvatinib was not inferior to sorafenib and improved survival to 13.6 (12.1-14.9) months (sorafenib 12.3 (10.4-13.99 months n.s.) (Kudo 2017). Quality of life scores deteriorated in both treatment groups after treatment with rather similar toxicity profiles: However, patients, who received lenvatinib, experienced fewer instances of palmar-plantar erythrodysaesthesia, diarrhoea and alopecia but more instances of arterial hypertension, proteinuria, dysphonia, and hypothyroidism. In summary,  lenvatinib has been approved in Japan, Europe and the US as a second, first-line treatment option in patients with advanced hepatocellular carcinoma. The safety of lenvatinib and its use in combination regimens is further evaluated in multiple ongoing studies.

Other antagonists targeting VEGFR, EGFR, ERBB2, Akt-mTor or Wnt/β-catenin signal transmission pathways have been evaluated in HCC. However, sunitinib, brivanib, linifanib, tivantinib, or the combination of erlotinib with sorafenib, everolimus and ramucirumab, all have failed to demonstrate relevant survival benefits.

Regorafenib (Stivarga®) is a small molecule multikinase inhibitor with structural analogy to sorafenib.  Regorafenib targets VEGF receptors 1-3, TIE2, PDGFRß, FGFR, RET, KIT, RAF kinase and MAPK thus intensively inhibits several pathways involved in angiogenesis, oncogenesis, metastasis and tumor immunity. In the RESORCE phase 3 trial regorafinib met its primary study endpoints and revealed prolonged survival (10.6 versus 7.8 months) and better disease control than placebo in patients who had failed on sorafenib (Bruix 2016). Thus, regorafenib has recently been licensed for HCC  patients progressing on first-line drug treatment. The most common adverse effects of regorafinib were rash and hand-foot syndrome, hypertension, increased AST, and hyperbilirubinemia. Similar to sorafenib skin toxicity with regorafinib was associated with improved overall survival (Bruix 2018). Of note, re-analysis of the data from the REFLECT study, where 75% of patients subsequently were treated with sorafenib, suggests that sorafenib may offer an alternative second-line treatment strategy for patients with HCC who had received lenvatinib as a first-line drug.

The multikinase inhibitor cabozantinib (Cabometyx®) is active against VEGFR2, c-MET, and AXL, as well as RET, Kit and FLT3. Beyond angiogenesis and oncogenesis inhibited kinases are implicated also in pathways of resistance to VEGFR inhibitors such as sorafenib. Consequentially cabozantinib was tested as a second-line treatment versus placebo in 707 patients with advanced HCC who received up to 2 prior system treatment regimens (including sorafenib) and who had disease progression (CELESTIAL trial) (Abou-Alfa GKI 2018).  In this study Cabozantinib substantially improved overall survival versus placebo (median 10.2 versus 8 months) and the benefit was more pronounced when patients had received  sorafenib as the only prior therapy (11.3 versus  7.2 months). Cabozantinib also achieved greater progression-free survival (5.2 versus 1.9 months),  and thus has become licensed as a second-line treatment option for patients failing on or intolerant to sorafenib. Dose reductions were frequent in the treatment arm (63%), often caused by side effects (16%) such as hand-foot skin reaction, hypertension, elevated liver enzymes, fatigue, diarrhoea, asthenia and decreased appetite. Thus, poor tolerability of cabozantinib may limit its use in clinical practice.

Ramucirumab (Cyramca®) is a humanized monoclonal antibody which selectively inhibits VEGFR2 and showed activity against HCC in early trials.  Of note, the REACH trial of ramucirumab against placebo indicated a survival benefit particularly for the subgroup of HCC patients with elevated AFP levels (Zhu 2015). This observation formed the basis for the biomarker-driven REACH-2 trial, which evaluated ramacirumab versus placebo in advanced HCC patients with failure of or intolerance to sorafenib and high AFP (≥400 ng/ml) (Zhu 2019).  REACH-2 met its primary study endpoint and confirmed that ramucirumab improved overall survival (8.5 versus 7.3 months, p=0.02) and progression free survival (2.8 versus 1.5 months, p<0.0001). A pooled safety and efficacy analysis of the REACH-2 trial with the patients who had AFP levels ≥400 ng/ml in the REACH study confirmed these findings (Zhou 2018), so that ramacirumab has been licensed as a biomarker-controlled second-line treatment for the subgroup of HCC patients with high AFP. Ramucirumab has a manageable safety profile with hypertension and hyponatriemia as the most common side effects, and on the other hand revealed declines in disease-releated symptoms, making it a second-line drug demonstrating both improved survival and quality of life.

Immune-based therapy. Currently cancer immunotherapy has become encouraging because monoclonal antibodies (mAbs), which block molecules that negatively regulate T-cell responses, can reverse T-cell exhaustion and reconstitute anti-tumour immunity (Prieto 2015). Immune checkpoint inhibitors, such as ipilimumab (anti-CTLA‑4), nivolumab (anti-PDL-1) and pembrolizumab (anti-PD-1) have already received approval from regulatory agencies for therapy of malignant melanoma, lung and renal cancer. Checkpoint inhibitors reactivate the exhausted antitumour response and can result in an objective and maintained immune control of tumour growth. Initial data from the CheckMate 040 study, an open-label phase 1/2 dose escalation and expansion trial with intravenous bi-weekly application of the PD-L1 antagonist nivolumab, reported 20% objective response rates across all underlying etiologies of liver cancer (El-Khoueiry 2017).  However, the results of a randomised controlled phase 3 trial, CheckMate 459, did not reach its primary study endpoint. The PD-1 inhibitor pembrolizumab induced complete remission, in 1% and partial remission in 16.3% of 104 patients with advanced liver cancer, who had disease progression on sorafenib in the KEYNOTE-224 phase 2 study but likewise failed to reach its primary study endpoint in the KEYNOTE-240 trial. Based on their phase II data both nivolumab (Opdivo®) and pembrolizumab (Keytruda®) were licensed for patients with advanced HCC in the US but not in Europe.  However, both antibodies are further evaluated as components in various combination rescue studies for patients with progressive HCC.

The spectrum of adverse effects associated with nivolumab and pembrolizumab comprises a variety of autoimmune and graft-versus-host-disease like reactions such as skin disease, diarrhoea, thyroiditis and autoimmune-like hepatitis but overall side effects appear still to be acceptable.

Recently, a phase III study comparing the combination of monoclonal antibodies atezolizumab and bevacizumab versus sorafenib (IMbrave150 study; Cheng AL et al. ESMO Asia 2019) has created new hope, because the combination resulted in substantially improved survival, delay of disease progression and quality of life across almost all groups of patients at acceptable adverse effects. However, patients with liver cancer of non-viral etiology appeared to have less benefit from this novel systemic treatment option.

Prophylaxis of liver cancer

Despite conspicuous progress in the diagnosis and therapy of HCC, the prognosis of HCC has not improved very much over time. Thus, prophylactic measures are of pivotal importance. HBV vaccination, now recommended by many national vaccination councils, has been proven in Taiwan to markedly reduce HBV infection rates along with the incidence of HCC as a complication of chronic hepatitis B in later life (Lok 2004).

Patients with chronic HBV and patients with chronic hepatitis C should be offered antiviral therapy as effective secondary prophylaxis of HCC. Although HBe antigen positive (van Zonneveld 2004) and HBe antigen negative patients with chronic hepatitis B showed reduced incidence rates of HCC when successfully treated with interferon (Papatheoridis 2001, Brunetto 2002, Lampertico 2003), antiviral therapy with nucleos(t)ide analogs seems to reduce the risk of HCC less convincingly (Papatheoridis 2010, Papatheoridis 2011). Newer, more potent nucleos(t)ide analogs such as entecavir seem to reduce the risk of HBV-associated liver cancer more potently, particularly in high risk patient groups (Hosaka 2012). Systematic analysis of the available data suggests that HBV-treatment can reduce the relative HCC risk by about 60%. Also, several meta-analyses suggest that successful interferon therapy will reduce the risk of HCC in chronic hepatitis C (Camma 2001, Paptheoridis 2001a, Veldt 2004).  Despite some initial confusion on the role of the newly available directly acting antiviral drugs in hepatitis C concering HCC prevention it has meanwhile become clear that rates of HCC development are substantially  diminished after DAA therapy (Carrat 2019) . Nevertheless, patients who have cirrhosis and/or long disease duration prior to antiviral therapy should be be followed in HCC surveillance programs, since their risk of liver cancer remains still high even after achieving a sustained virological response (Yu 2006, Van der Meer 2012, Aleman 2013).

Improving additional risk factors such as obesity and poorly controlled diabetes mellitus may further reduce the risk of HCC development: weight reduction and exercise improve the prognosis of steatohepatitis, and metformin and thiazolidinedione should be favoured over sulfonylurea drugs in the treatment of diabetes (Greten 2013). The use of aspirin but not other nonsteroidal antiinflammatory drugs was associated with a decreased risk of HCC in a US Diet and Health study (Sahasrabuddhe 2012), and several studies suggest that use of statins leads to a lower risk of HCC (Singh 2013, Shi 2014, Hsiang 2015). Finally, daily consumption of two or more cups of coffee reduces the risk of HCC by 40-50% in patients with chronic viral hepatitis (Gelatti 2005, Bravi 2007, Larsson 2007, Wakai 2007).

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