MONDAY, Oct. 13 (HealthDay News) -- Although high caffeine consumption does not appear to increase the overall risk of breast cancer, it may be associated with an increased risk of breast cancer in women with benign breast disease, and for the development of estrogen receptor-negative and progesterone receptor-negative breast cancer and tumors larger than 2 centimeters, according to study findings published in the Oct. 13 issue of the Archives of Internal Medicine.
Ken Ishitani, M.D., of Brigham and Womens Hospital and Harvard Medical School in Boston, and colleagues studied 38,432 women who were cancer-free in 1992-1995, including 1,188 who developed invasive breast cancer during a mean follow-up of 10 years.
Overall, the researchers found that women who drank at least four cups of coffee or at least two cups of tea per day did not have a higher risk of breast cancer than women who almost never drank these beverages. In women with benign breast disease, they found a borderline significant association between the highest quintile of caffeine consumption and increased risk (relative risk 1.32). They also found a positive association between caffeine consumption and the risk of estrogen receptor-negative and progesterone receptor-negative breast cancer and tumors larger than 2 centimeters (RRs, 1.68 and 1.79, respectively).
"We cannot exclude the possibility that the findings in some subgroups may be the result of chance because a large number of subgroups were evaluated," the authors write. "More studies are needed to refute or confirm the associations observed in some subgroups."
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