Hepatitis C virus
(HCV) infection is associated with a range of non-liver-related cancers,
investigators from the United States report in Cancer. The study population comprised over 1.6m elderly people with cancer and 200,000 closely matched cancer-free controls. Overall, cancer
incidence was higher among people with HCV antibodies, as was incidence of
several specific malignancies including cancers of the liver, bile ducts,
pancreas, certain skin cancers, myelodysplastic syndrome, and diffuse large
B-cell lymphoma. The investigators estimated that elimination of HCV infection
would have only a modest effect on the risk of many of these cancers.
“Our analyses of a
large, population-based data set of elderly individuals demonstrate that, along
with HCC [hepatocellular carcinoma], several additional cancers are associated
with HCV infection,” comment the investigators. “Although the introduction of
direct-acting antivirals has dramatically improved cure rates, HCC risk still
remains relatively high in infected individuals who have cleared the virus –
particularly elderly individuals.”
An estimated 3m
individuals in the United States have HCV infection. Many of these
infections involve individuals born between 1945 and 1965, the “Baby Boomer”
generation. This age group has been prioritised for HCV screening.
Glossary
- extrahepatic
Something that has an
effect outside the liver, for example when viral hepatitis affects the kidneys
or causes depression.
- lymphoma
A
type of tumour affecting the lymph nodes.
HCV infection is
known to increase the risk of HCC and non-Hodgkin lymphoma. Some data suggest
that the infection also increases the risk of other cancers.
However, few
studies have examined the association between HCV infection and
non-liver-related cancers. A team of US investigators therefore analysed data
collection via the Surveillance, Epidemiology and End Results (SEER)
surveillance programme to determine the association between HCV and the risk of
43 specific cancers. Because of the ageing of the Baby Boomer generation, the
investigators focused on people aged 66 years and older.
Elderly people
receiving care between 1993 and 2011 were eligible for inclusion. The authors
identified 1,623,538 people with cancer. These individuals were matched with
cancer-free individuals of the same age, sex, race and calendar year of follow-up.
Prevalence of HCV
and hepatitis B virus (HBV) was higher among people with cancer compared to the controls (0.7%
vs 0.5%; 1.2% vs 1.1%). A similar proportion of people in both groups had HIV infection (0.4%). Although the differences were small, compared to the
controls, people with cancer had a higher prevalence of cirrhosis, diabetes
mellitus, smoking and drug abuse. They were also more likely to be high school
graduates and to reside in areas with higher median incomes.
Overall, HCV
prevalence was higher among cases than controls (0.7% vs 0.5%; aOR = 1.32; 95%
CI, 1.32-1.42, p < 0.001).
Moreover,
there was a significant association between HCV and an increased risk of
several specific cancers:
- Liver (aOR = 31.5; 95% CI,
29.0-34.3)
- Intrahepatic bile duct (aOR = 3.40;
95% CI, 2.52-4.58)
- Extrahepatic bile duct (aOR = 1.90;
95% CI, 1.41-2.57)
- Pancreas (aOR = 1.23; 95% CI,
1.09-1.40)
- Anus (aOR = 1.97; 95% CI,
1.42-2.73)
- Non-melanoma non-epithelial
skin cancer (aOR = 1.53; 95% CI, 1.15-2.04)
- Myelodysplastic syndrome (MDS)
(aOR = 1.56; 95% CI, 1.33-1.93)
- Diffuse large B-cell lymphoma
(DLBCL) (aOR = 1.57; 95% CI, 1.34-1.84)
The associations
between HCV and these cancers remained in sensitivity analyses excluding
people with HIV and HBV and restricted to people without documented alcohol
abuse or cirrhosis.
The investigators
estimated that eliminating HCV would reduce the risk of liver cancer by 16%.
However, elimination would only have a modest impact on the risk of cancers of
the bile ducts, pancreas, MDS and DLBCL (1.15%-0.28%).
“We observed
significant associations between HCV infection and several cancers other than
liver cancer, notably intrahepatic and extrahepatic cholangiocarcinomas and
DLBCL,” conclude the authors. “Studies are needed to strengthen the evidence
linking HCV infection to these cancers and to further elucidate biological
mechanisms.”