A study of Japanese atomic bomb survivors shows that men exposed to radiation were more likely to develop breast cancer than others who weren’t exposed.

Yes, men can develop breast cancers, but it is fairly rare. In most countries, about 1 of every 100 cases of breast cancer occur in men.

The new findings add to earlier reports suggesting that radiation exposure raises the risk of male breast cancer, lead author Dr. Elaine Ron, from the National Cancer Institute, Bethesda, Maryland, and colleagues note.

The current study, reported in the Journal of the National Cancer Institute, involved 32,411 male subjects who were exposed to a known radiation dose, 2978 exposed to an unknown dose, and 10,491 unexposed subjects.

Nine men exposed to radiation developed breast cancer, which translates to the equivalent of 1.8 cases per 10,000 men over a 10-year period. By contrast, three men in the unexposed group developed this malignancy, yielding a significantly lower rate of 0.5 cases per 10,000 persons per 10 years.

In addition, the authors found that the risk of male breast cancer was directly related to the dose of radiation the men received.

“Because male breast cancer is a rare disease, few cases were seen in this 40-year follow-up of a large cohort,” the researchers point out. “However, the results clearly show an association between exposure to external radiation and the occurrence of male breast cancer.”

SOURCE: Journal of the National Cancer Institute, April 20, 2005.