May 8, 2007 — Patients with hepatitis C have a 20% to 30% increased risk of
developing non-Hodgkin's lymphoma and a 3-fold higher risk of developing
Waldenström's macroglobulinemia, a low-grade lymphoma. "We demonstrated that
infection precedes development of these outcomes and that the risk in
individuals infected with hepatitis C is consistently increased, with more than
5 years of follow-up," reports the team led by Thomas Giordano, MD, from the
Baylor College of Medicine and the Michael E. DeBakey Veterans Affairs (VA)
Medical Center in Houston, Texas. Risks were also increased for cryoglobulinemia.
The study appears in the May 9 issue of the Journal of the American Medical
Association.
"Our cohort study of 718,687 veterans with more than 1.37
million person-years of follow-up is the largest study conducted to our
knowledge on the risk conferred by hepatitis C infection for hematopoietic
malignancies, related lymphoproliferative disorders, and thyroid cancer," the
researchers point out. Could screening infected patients help identify
early-stage lymphoproliferative conditions for early intervention? The authors
say it is still too early to know and that additional epidemiological and
pathophysiological studies are needed to clarify this question.
Hepatitis C is an RNA virus that causes chronic hepatitis,
cirrhosis, and hepatocellular carcinoma. Hepatitis C is primarily acquired
through parenteral exposures such as injection drug use and blood transfusions.
The prevalence in the general population in the United States is estimated to be
1.6%, with approximately 4.1 million people infected and living in the United
States. Hepatitis C is more common in military veterans who use the VA medical
system, and an estimated 5% of patients are infected.
The incidence of cancer in US military veterans is also
higher than in the general population, and the rates in the present analysis
were reportedly increased as well. "This increase may reflect the high
prevalence among veterans of chronic medical conditions, poverty, or use of
tobacco or alcohol," the researchers suggest.
Dr. Giordano and his team conducted a retrospective cohort
study of veterans to test the hypothesis that hepatitis C infection is linked to
an increased risk for malignancies of the blood and blood-forming tissues,
related disorders, and thyroid cancer. The study included 146,394 patients
infected with hepatitis C and another 572,293 without the virus. The mean age of
patients was 52 years and 97% were men.
Patients with Hepatitis C at Increased Risk for Malignancy
Outcome
Adjusted Hazard
Ratio
95% CI
Adjusted P-value
Non-Hodgkin's
lymphoma (n=1359)
1.28
1.12 – 1.45
< .0038
Waldenström's
macroglobulinemia (n=165)
2.76
2.01 – 3.79
< .0038
Cryoglobulinemia
(n=551)
3.98
3.36 – 4.72
< .0038
"We found no significantly increased risk for other
hematological malignancies," the researchers note. Although thyroiditis risk
was slightly increased, the risk for thyroid cancer (n=320) was not
(adjusted hazard ratio, 0.72; 95% CI, 0.52 – 0.99), they report.
The researchers point to a number of limitations to their
work. For example, they did not validate the cancer diagnoses through a
separate chart review and relied instead on information coded in patient
files. In addition, the coding system did permit the group to distinguish
various pathological subtypes, which, they say, should be a goal of future
research.
"Nonetheless, there is no reason to suspect that the
overall accuracy or reliability of the diagnostic recording for the outcomes
would differ by hepatitis C infection status. Second, because the study was
conducted with VA data, very few women were included. Third, we did not have
data on some known or postulated risk factors for non-Hodgkin's lymphoma
such as family history and pesticide exposure," they add.
Despite the limitations, Dr. Giordano and his team
conclude, "These results support an etiological role for hepatitis C in
causing lymphoproliferation and causing non-Hodgkin's lymphoma."
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