The link between chronic hepatitis B virus (HBV) infection and hepatocellular carcinoma (HCC or primary liver cancer) is well established, but recent studies have spurred renewed interest in a possible association between HBV and pancreatic cancer, which may have important implications for the prevention and management of this deadly cancer.
The liver and pancreas are located close to
one another and share common blood vessels
and ducts. As a result, the pancreas may serve
as a target organ for HBV. Moreover, many
patients with acute and chronic HBV infection
have elevated levels of a pancreatic enzyme,
indicating pancreatic damage.
Linking Hepatitis B and
Pancreatic Cancer
Researchers at the MD Anderson Cancer
Center in Houston found that past exposure to
HBV, but not to the hepatitis C virus (HCV),
was significantly higher among patients with
pancreatic cancer than among control subjects.
The study additionally found that the risk of
pancreatic cancer was higher among diabetic
patients with HBV infection.
Previous research has demonstrated an association between diabetes and chronic hepatitis B in the development of HCC. The recent findings raise the possibility that the joint effect of HBV and diabetes may increase susceptibility to chronic inflammation, DNA damage, and the development of pancreatic cancer.
Possible Disease Mechanisms
Several mechanisms for HBV-associated
pancreatic cancer have been proposed. HBV
may play a direct pathogenic role in pancreatic
cancer, as it does in HCC, by integrating into
pancreatic cells and contributing to chromosomal
instability. HBV also may promote
chronic inflammation in the pancreas, which
encourages the development of potentially
cancer-promoting mutations.
Alternatively another virus, similar to HBV, may cause pancreatic cancer. Given that an association between HCV and pancreatic cancer was not found, it is likely that HBV-DNA integration plays a greater role than does direct inflammation. Lastly, it is possible that a carcinogenic trigger may activate susceptibility genes in individuals with pancreatic cancer.
What does this mean for
people with HBV?
According to W. Thomas London, MD,
Board Member and Medical Advisor,
Hepatitis B Foundation, and Senior
Member, Fox Chase Cancer Center,
people with possible occult HBV infections
(meaning they harbor undetectable
levels of virus but do not test positive
for an HBV infection) may experience
reactivation of an HBV infection if they
undergo chemotherapy or immunosuppressive
therapy that could potentially
lead to hepatic failure. This possibility
underscores the need for oncologists to
consider checking HBV status of patients
before beginning chemotherapy, particularly
in those with evidence of past
exposure to HBV.
Hepatologists should also collaborate with oncologists to develop guidelines for the management of HBV infection in patients with cancer prior to initiation of chemotherapy and should closely monitor such patients during chemotherapy.
What are the implications?
Pancreatic cancer is one of the most
lethal cancers, with an overall 5-year
survival rate of only 5 percent. If chronic
HBV infection plays a causative role, it
represents a readily modifiable risk factor
for a deadly cancer, notes Baruch
Blumberg, MD, PhD, Distinguished
Scholar, Hepatitis B Foundation, and
Senior Advisor to the President, Fox
Chase Cancer Center.
Dr. Blumberg explained that over 15 years of data indicate that vaccination against HBV can significantly decrease the incidence of HCC or primary liver cancer. Further evidence suggests that antiviral treatment of HBV can significantly decrease the risk as well.
“Healthcare professionals need to be more aware of the link [between viruses and cancer],” stated Blumberg. Given that no screening test exists for pancreatic cancer and management options are severely limited, this possible link is particularly significant and offers the prospect of new strategies in anti-cancer prevention and treatment.
Blumberg contends that “cancer prevention with vaccines and other measures and cancer treatment with antivirals is a new and potentially less damaging approach [compared with chemotherapy].”
Considerations for future research Further studies are needed to confirm a causative role for HBV in pancreatic cancer. Blumberg recommends that researchers study the incidence of pancreatic cancer over time in different countries, including those that have instituted HBV vaccination programs.
Anu Hosagandi, medical writer Bucks County, PA
