Epidemiology

Blood transfusions, possibly HCV, tied to thyroid cancer risk

Last Updated: 2004-11-12 16:24:25 -0400 (Reuters Health)

NEW YORK - New research from Japan provides indirect evidence for a link between hepatitis C virus (HCV) infection and thyroid cancer.

The prospective cohort study found blood transfusion--the main means of HCV transmission in Japan until 1992--"marginally" increased thyroid cancer risk. The findings "indirectly" support an association between HCV and thyroid cancer, Dr. Yoshihisa Fujino of the University of Occupational and Environmental Health and colleagues conclude, while raising the possibility that immunomodulation associated with transfusion could foster progression from thyroiditis to cancer.

Recent case-control studies have linked HCV and thyroid cancer, Dr. Fujino and his team note in their report in the Nov. 20 issue of the International Journal of Cancer. HCV infection has been tied to autoimmune conditions, including autoimmune thyroiditis, they explain, which can be a precursor to thyroid cancer.

But because HCV only was identified in 1988, few cohort studies before 1990 included testing for the virus. For this reason, the current study used blood transfusion history as a proxy for HCV infection.

The researchers collected data on a subset of participants in the Japan Collaborative Cohort Study for Evaluation of Cancer Risk, a cohort study of 110,792 men and women that began in 1988-1990. The current study included 37,983 women free from cancer at the study's outset, 79 of whom developed thyroid cancer during the study.

Women who had blood transfusions showed a 77% increased risk of thyroid cancer, while blood transfusion and/or liver disease increased risk by 84%. Among study participants, 11.5% of transfusion recipients had a history of liver disease, compared to 5.3% of individuals who had not had transfusions, suggesting that combining both transfusion history and liver disease "captured" more individuals with HCV, the researchers note.

"Detailed epidemiological studies will be necessary to further examine the interactions between thyroid cancer, HCV and blood transfusion, including immunomodulation effects," they conclude.

Int J Cancer 2004;112:722-725.