While the prevalence of a number of cancers is declining, some types are on the rise. The incidence of one of the more difficult forms of liver cancer to treat has tripled over the past 30 years. And researchers are beginning to know why.
Hepatitis C infection wreaks havoc on the liver, leaving tissue scarred and permanently damaged. Researchers now believe it's the rise in cases of hepatitis C that's behind the greatest increases in hepatocellular carcinoma (HCC) - liver cancer. Obesity also plays a role in this trend.
study from the Mayo Clinic led by Ray Kim, M.D., a specialist in Gastroenterology and Hepatology, reviewed several decades of data from the Rochester Epidemiology Project. This review uncovered a couple of interesting facts:- The overall incidence of HCC is higher than what the National Cancer Institute (NCI) estimates - 6.9 cases are found in 100,000 individuals vs. NCI's estimate of 5.1 per 100,000.
- Two decades ago, liver cancer typically resulted from tissue scarring caused by alcohol consumption or cirrhosis.
- HCC is now developing after an individual is infected with the hepatitis C virus.
“The liver scarring from hepatitis C can take 20 to 30 years to develop into cancer,” Dr. Kim says. “We’re now seeing cancer patients in their 50s and 60s who contracted hepatitis C 30 years ago and didn’t even know they were infected,” he said.
Along with liver diseases, 11 percent of HCC cases were associated with obesity, especially fatty liver disease. Dr. Kim believes that due to the nation's burgeoning obesity crisis, rates of liver cancer "may dramatically increase in the foreseeable future.”
“It’s a small percentage of cases overall,” Dr. Kim says. “But with the nationwide obesity epidemic, we believe the rates of liver cancer may dramatically increase in the foreseeable future.”
Another study led by Mayo Clinic researcher Abdirashid Shire, Ph.D, examined Somali immigrants. Hepatitis B, also a risk factor for HCC, is common in that country. Researchers were surprised to learn that even in this population, though, hepatitis C was the primary cause of liver cancer.
Both studies suggest individuals at greatest risk for liver cancer - people who have had hepatitis C and those who were born in countries where hepatitis is more frequent - should be screened for liver cancer, which is most treatable when it's detected early.
These two studies were funded by the National Institutes of Health and the Mayo Clinic Center for Translational Science Activities.
Findings from this research were published in the January issue of Mayo Clinic Proceedings.
The American Cancer Society estimates that there are over 26,000 new cases of primary liver cancer and bile duct cancer in the United States each year, and they are responsible for over 19,000 deaths. The average man has about a 1% chance of developing this cancer over his lifetime, while the average woman has about a half percent chance.
Primary liver cancer most commonly includes hepatocellular carcinoma (HCC) and can coexist with cholangiocarcinoma, a cancer of the bile ducts between the liver and gall bladder. It is important to note that most cases of cancer in the liver are metastases from other cancers, such as those from the colon, breast, or prostate. Primary liver cancers begin in the liver itself. Other less common forms of primary liver cancer include angiosarcomas and hemangiosarcomas (cancers that begin in the blood vessels of the liver), lymphoma of the liver, and hepatoblastoma (a rare pediatric cancer usually occurring in children under three years of age). There are also several variants of benign liver tumors. Hepatocellular adenomas (a benign liver tumor associated with oral contraceptive use and glycogen storage disease) must be watched closely, as they have a potential to turn cancerous.
Hepatocellular carcinoma, the most common form of liver cancer, is strongly associated with infection by chronic hepatitis B and C. These infections cause liver cancer more often in Asian and African countries where hepatitis viruses are endemic and people acquire the disease early in their life.
Cases of liver cancer in the United States have tripled over the past three decades. While the most common cause of liver cancer used to be from alcohol abuse and the resulting cirrhosis of the liver, hepatitis C infection is now a leading cause. Obesity, particularly fatty liver disease, is also implicated. Other causes include hemochromatosis (a disease that causes the body to store too much iron), high exposure to aflatoxins (a mold found in peanuts, rice, soybeans and corn; rare in developed countries), and Type 2 diabetes.
Symptoms of HCC usually present with classic signs of liver dysfunction such as jaundice (yellowing of the skin due to too much bilirubin), bruising and blood clotting problems (due to the liver making the clotting factors in our blood), and ascites (fluid buildup in the abdomen from liver dysfunction). Other general symptoms include nausea, fatigue, vomiting, and unintentional weight loss.
In patients who are at high risk for HCC, screening is usually done with ultrasound and CT scan, as well as MRI. While there is no reliable blood test for liver cancer screening, a high level of alpha-fetoprotein (AFP) should be considered suspicious for liver cancer. Liver biopsy is also done, although this is not necessary for diagnosis if imaging is definitive.
Treatment for HCC is difficult, as many patients with liver cancer also have damaged livers from cirrhosis. Treatment must be balanced between treating the cancer and also mitigating the risk of liver failure. Early stage cancer has the potential for surgical removal, however most cases of liver cancer are discovered when they are advanced, making surgery difficult. Other treatments are dependent on the size and location of the tumors, such as ethanol injection into the tumor (small tumors), radiofrequency ablation (using high-frequency radiowaves to destroy the tumor), transcatheter arterial chemoembolization (cuts off the blood supply to unresectable tumors), and cryosurgery (destroying cancerous tissue with subzero temperatures). Liver transplantation is a relatively successful option for patients without metastatic spread. Sorafenib (marketed as Nexavar) is a tyrosine kinase inhibitor that has shown efficacy in treating HCC.
Ultimately, HCC is a difficult cancer to treat and survival rates are low, with most cancers being unable to be completely removed. These patients usually succumb to the disease within three to six months. Across the board, patients with a solitary small tumor of less than three centimeters in size have a five-year survival rate of 20%. Patients with advanced disease have a one-year survival rate of 30%.
Prevention of liver cancer is extremely effective if vaccinated against hepatitis B. Avoidance of alcohol abuse is also effective. Other patients with different causes of cirrhosis or chronic liver inflammation will benefit from routine ultrasound screening and AFP measurements in the hope of detecting cancer early.
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