Liver Cancer
Hepatocellular carcinoma (HCC) is the most common type of primary liver cancer in adults, and is the most common cause of death in people with cirrhosis.
It occurs in the setting of chronic liver inflammation, and is most closely linked to chronic viral hepatitis infection (hepatitis B or C) or exposure to toxins such as alcohol or aflatoxin. Certain diseases, such as hemochromatosis and alpha 1-antitrypsin deficiency, markedly increase the risk of developing HCC. Metabolic syndrome and NASH are also increasingly recognized as risk factors for HCC.
As with any cancer, the treatment and prognosis of HCC vary depending on the specifics of tumor histology, size, how far the cancer has spread, and overall health.
The vast majority of HCC occurs in Asia and sub-Saharan Africa, in countries where hepatitis B infection is endemic and many are infected from birth. The incidence of HCC in the United States and other developing countries is increasing due to an increase in hepatitis C virus infections. It is more common in males than females for unknown reasons.
Signs and symptoms
Most cases of HCC occur in people who already have signs and symptoms of chronic liver disease. They may present either with worsening of symptoms or may be without symptoms at the time of cancer detection. HCC may directly present with yellow skin, abdominal swelling due to fluid in the abdominal cavity, easy bruising from blood clotting abnormalities, loss of appetite, unintentional weight loss, abdominal pain, nausea, vomiting, or feeling tired.
Most cases of HCC occur in people who already have signs and symptoms of chronic liver disease. They may present either with worsening of symptoms or may be without symptoms at the time of cancer detection. HCC may directly present with yellow skin, abdominal swelling due to fluid in the abdominal cavity, easy bruising from blood clotting abnormalities, loss of appetite, unintentional weight loss, abdominal pain, nausea, vomiting, or feeling tired.
Risk factors
HCC mostly occurs in people with cirrhosis of the liver, and so risk factors generally include factors which cause chronic liver disease that may lead to cirrhosis. Still, certain risk factors are much more highly associated with HCC than others. For example, while heavy alcohol consumption is estimated to cause 60–70% of cirrhosis, the vast majority of HCC occurs in cirrhosis attributed to viral hepatitis (although there may be overlap).[4] Recognized risk factors include:
Chronic viral hepatitis (estimated cause of 80% cases globally)
Chronic hepatitis B (about 50% cases)
Chronic hepatitis C (about 25% cases)[5]
Toxins:
Alcohol abuse: the most common cause of cirrhosis[4]
Aflatoxin
Iron overload state (hemochromatosis)
Metabolic:
Nonalcoholic steatohepatitis: up to 20% progress to cirrhosis [6]
Type 2 diabetes (probably aided by obesity)[7]
Congenital disorders:
Alpha 1-antitrypsin deficiency
Wilson's disease (controversial; while some theorise the risk increases,[8] case studies are rare[9] and suggest the opposite where Wilson's disease actually may confer protection
HCC mostly occurs in people with cirrhosis of the liver, and so risk factors generally include factors which cause chronic liver disease that may lead to cirrhosis. Still, certain risk factors are much more highly associated with HCC than others. For example, while heavy alcohol consumption is estimated to cause 60–70% of cirrhosis, the vast majority of HCC occurs in cirrhosis attributed to viral hepatitis (although there may be overlap).[4] Recognized risk factors include:
Chronic viral hepatitis (estimated cause of 80% cases globally)
Chronic hepatitis B (about 50% cases)
Chronic hepatitis C (about 25% cases)[5]
Toxins:
Alcohol abuse: the most common cause of cirrhosis[4]
Aflatoxin
Iron overload state (hemochromatosis)
Metabolic:
Nonalcoholic steatohepatitis: up to 20% progress to cirrhosis [6]
Type 2 diabetes (probably aided by obesity)[7]
Congenital disorders:
Alpha 1-antitrypsin deficiency
Wilson's disease (controversial; while some theorise the risk increases,[8] case studies are rare[9] and suggest the opposite where Wilson's disease actually may confer protection
Hemophilia, although statistically associated with higher risk of HCC,[11] this is due to coincident chronic viral hepatitis infection related to repeated blood transfusions over lifetime.
The significance of these risk factors varies globally. In regions where hepatitis B infection is endemic, such as southeast China, this is the predominant cause.[13] In populations largely protected by hepatitis B vaccination, such as the United States, HCC is most often linked to causes of cirrhosis such as chronic hepatitis C, obesity, and alcohol abuse.
Certain benign liver tumors, such as hepatocellular adenoma, may sometimes be associated with coexisting malignant HCC. Evidence is limited for the true incidence of malignancy associated with benign adenomas; however, the size of hepatic adenoma is considered to correspond to risk of malignancy and so larger tumors may be surgically removed. Certain subtypes of adenoma, particularly those with β-catenin activation mutation, are particularly associated with increased risk of HCC.
Children and adolescents are unlikely to have chronic liver disease, but if they suffer from congenital liver disorders, this fact increases the chance of developing HCC.[14] Specifically, children with biliary atresia, infantile cholestasis, glycogen-storage diseases, and other cirrhotic diseases of the liver are predisposed to developing HCC in childhood.
Young adults afflicted by the rare fibrolamellar variant of hepatocellular carcinoma may have none of the typical risk factors, i.e. cirrhosis and hepatitis.
Diabetes mellitus
The risk of hepatocellular carcinoma in type 2 diabetics is greater (from 2.5 to 7.1 times the nondiabetic risk) depending on the duration of diabetes and treatment protocol. A suspected contributor to this increased risk is circulating insulin concentration such that diabetics with poor insulin control or on treatments that elevate their insulin output (both states that contribute to a higher circulating insulin concentration) show far greater risk of hepatocellular carcinoma than diabetics on treatments that reduce circulating insulin concentration. On this note, some diabetics who engage in tight insulin control (by keeping it from being elevated) show risk levels low enough to be indistinguishable from the general population. This phenomenon is thus not isolated to diabetes mellitus type 2, since poor insulin regulation is also found in other conditions such as metabolic syndrome (specifically, when evidence of nonalcoholic fatty liver disease or NAFLD is present) and again evidence of greater risk exists here, too While there are claims that anabolic steroid abusers are at greater risk (theorized to be due to insulin and IGF exacerbation[21][22]), the only evidence that has been confirmed is that anabolic steroid users are more likely to have hepatocellular adenomas (a benign form of HCC) transform into the more dangerous hepatocellular carcinoma
The significance of these risk factors varies globally. In regions where hepatitis B infection is endemic, such as southeast China, this is the predominant cause.[13] In populations largely protected by hepatitis B vaccination, such as the United States, HCC is most often linked to causes of cirrhosis such as chronic hepatitis C, obesity, and alcohol abuse.
Certain benign liver tumors, such as hepatocellular adenoma, may sometimes be associated with coexisting malignant HCC. Evidence is limited for the true incidence of malignancy associated with benign adenomas; however, the size of hepatic adenoma is considered to correspond to risk of malignancy and so larger tumors may be surgically removed. Certain subtypes of adenoma, particularly those with β-catenin activation mutation, are particularly associated with increased risk of HCC.
Children and adolescents are unlikely to have chronic liver disease, but if they suffer from congenital liver disorders, this fact increases the chance of developing HCC.[14] Specifically, children with biliary atresia, infantile cholestasis, glycogen-storage diseases, and other cirrhotic diseases of the liver are predisposed to developing HCC in childhood.
Young adults afflicted by the rare fibrolamellar variant of hepatocellular carcinoma may have none of the typical risk factors, i.e. cirrhosis and hepatitis.
Diabetes mellitus
The risk of hepatocellular carcinoma in type 2 diabetics is greater (from 2.5 to 7.1 times the nondiabetic risk) depending on the duration of diabetes and treatment protocol. A suspected contributor to this increased risk is circulating insulin concentration such that diabetics with poor insulin control or on treatments that elevate their insulin output (both states that contribute to a higher circulating insulin concentration) show far greater risk of hepatocellular carcinoma than diabetics on treatments that reduce circulating insulin concentration. On this note, some diabetics who engage in tight insulin control (by keeping it from being elevated) show risk levels low enough to be indistinguishable from the general population. This phenomenon is thus not isolated to diabetes mellitus type 2, since poor insulin regulation is also found in other conditions such as metabolic syndrome (specifically, when evidence of nonalcoholic fatty liver disease or NAFLD is present) and again evidence of greater risk exists here, too While there are claims that anabolic steroid abusers are at greater risk (theorized to be due to insulin and IGF exacerbation[21][22]), the only evidence that has been confirmed is that anabolic steroid users are more likely to have hepatocellular adenomas (a benign form of HCC) transform into the more dangerous hepatocellular carcinoma
Pathogenesis
Hepatocellular carcinoma, like any other cancer, develops when epigenetic alterations and mutations affecting the cellular machinery cause the cell to replicate at a higher rate and/or result in the cell avoiding apoptosis.[25]
In particular, chronic infections of hepatitis B and/or C can aid the development of hepatocellular carcinoma by repeatedly causing the body's own immune system to attack the liver cells, some of which are infected by the virus, others merely bystanders.[26] Activated immune-system inflammatory cells release free radicals, such as reactive oxygen species and nitric oxide reactive species, which in turn can cause DNA damage and lead to carcinogenic gene mutations.[27] Reactive oxygen species also cause epigenetic alterations at the sites of DNA repair.[28]
While this constant cycle of damage followed by repair can lead to mistakes during repair, which in turn lead to carcinogenesis, this hypothesis is more applicable, at present, to hepatitis C. Chronic hepatitis C causes HCC through the stage of cirrhosis. In chronic hepatitis B, however, the integration of the viral genome into infected cells can directly induce a noncirrhotic liver to develop HCC. Alternatively, repeated consumption of large amounts of ethanol can have a similar effect. The toxin aflatoxin from certain Aspergillus species of fungi is a carcinogen and aids carcinogenesis of hepatocellular cancer by building up in the liver. The combined high prevalence of rates of aflatoxin and hepatitis B in settings such as China and West Africa has led to relatively high rates of hepatocellular carcinoma in these regions. Other viral hepatitides such as hepatitis A have no potential to become a chronic infection, thus are not related to HCC.
In particular, chronic infections of hepatitis B and/or C can aid the development of hepatocellular carcinoma by repeatedly causing the body's own immune system to attack the liver cells, some of which are infected by the virus, others merely bystanders.[26] Activated immune-system inflammatory cells release free radicals, such as reactive oxygen species and nitric oxide reactive species, which in turn can cause DNA damage and lead to carcinogenic gene mutations.[27] Reactive oxygen species also cause epigenetic alterations at the sites of DNA repair.[28]
While this constant cycle of damage followed by repair can lead to mistakes during repair, which in turn lead to carcinogenesis, this hypothesis is more applicable, at present, to hepatitis C. Chronic hepatitis C causes HCC through the stage of cirrhosis. In chronic hepatitis B, however, the integration of the viral genome into infected cells can directly induce a noncirrhotic liver to develop HCC. Alternatively, repeated consumption of large amounts of ethanol can have a similar effect. The toxin aflatoxin from certain Aspergillus species of fungi is a carcinogen and aids carcinogenesis of hepatocellular cancer by building up in the liver. The combined high prevalence of rates of aflatoxin and hepatitis B in settings such as China and West Africa has led to relatively high rates of hepatocellular carcinoma in these regions. Other viral hepatitides such as hepatitis A have no potential to become a chronic infection, thus are not related to HCC.
DiagnosisMethods of diagnosis in HCC have evolved with the improvement in medical imaging. The evaluation of both asymptomatic patients and those with symptoms of liver disease involves blood testing and imaging evaluation. Although historically a biopsy of the tumor was required to prove the diagnosis, imaging (especially MRI) findings may be conclusive enough to obviate histopathologic confirmation.
Treatment
Treatment of hepatocellular carcinoma varies by the stage of disease, a person's likelihood to tolerate surgery, and availability of liver transplant:
Curative intention: for limited disease, when the cancer is limited to one or more areas of within the liver, surgically removing the malignant cells may be curative. This may be accomplished by resection the affected portion of the liver (partial hepatectomy) or in some cases by orthotopic liver transplantation of the entire organ.
"Bridging" intention: for limited disease which qualifies for potential liver transplantation, the person may undergo targeted treatment of some or all of the known tumor while waiting for a donor organ to become available.[47]
"Downstaging" intention: for moderately advanced disease which has not spread beyond the liver, but is too advanced to qualify for curative treatment. The person may be treated by targeted therapies in order to reduce the size or number of active tumors, with the goal of once again qualifying for liver transplant after this treatment.[47]
Palliative intention: for more advanced disease, including spread of cancer beyond the liver or in persons who may not tolerate surgery, treatment intended to decrease symptoms of disease and maximize duration of survival.
Loco-regional therapy (also referred to as liver-directed therapy) refers to any one of several minimally-invasive treatment techniques to focally target HCC within the liver. These procedures are alternatives to surgery, and may be considered in combination with other strategies, such as a later liver transplantation.[48] Generally, these treatment procedures are performed by interventional radiologists or surgeons, in coordination with a medical oncologist. Loco-regional therapy may refer to either percutaneous therapies (e.g. cryoablation), or arterial catheter-based therapies (chemoembolization or radioembolization)
Curative intention: for limited disease, when the cancer is limited to one or more areas of within the liver, surgically removing the malignant cells may be curative. This may be accomplished by resection the affected portion of the liver (partial hepatectomy) or in some cases by orthotopic liver transplantation of the entire organ.
"Bridging" intention: for limited disease which qualifies for potential liver transplantation, the person may undergo targeted treatment of some or all of the known tumor while waiting for a donor organ to become available.[47]
"Downstaging" intention: for moderately advanced disease which has not spread beyond the liver, but is too advanced to qualify for curative treatment. The person may be treated by targeted therapies in order to reduce the size or number of active tumors, with the goal of once again qualifying for liver transplant after this treatment.[47]
Palliative intention: for more advanced disease, including spread of cancer beyond the liver or in persons who may not tolerate surgery, treatment intended to decrease symptoms of disease and maximize duration of survival.
Loco-regional therapy (also referred to as liver-directed therapy) refers to any one of several minimally-invasive treatment techniques to focally target HCC within the liver. These procedures are alternatives to surgery, and may be considered in combination with other strategies, such as a later liver transplantation.[48] Generally, these treatment procedures are performed by interventional radiologists or surgeons, in coordination with a medical oncologist. Loco-regional therapy may refer to either percutaneous therapies (e.g. cryoablation), or arterial catheter-based therapies (chemoembolization or radioembolization)
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