The scientists, led by Louise Brinton, Ph.D., and Michael B. Cook, Ph.D., NCI, observed a small but statistically significantly elevated risk for breast cancer in men with a high body mass index (BMI). Men with the highest BMI had a 35 percent greater risk of breast cancer compared to men with the lowest BMI. The elevated risk observed with men who have a high BMI (who often have excess breast tissue and elevated estrogen levels) appears similar to the pattern for breast cancer risk in postmenopausal women. It was also determined that gynecomastia, independent from both Klinefelter syndrome and obesity, was associated with a 10-fold increased risk of breast cancer in men. As a next step, Brinton plans to follow up these findings with a deeper analysis of the effects of naturally occurring hormones on the risk of breast cancer in men by testing hormone levels in biological samples available from some of the studies involved with the project.
Source: National Cancer Institute