Breast cancer among men remains a tiny risk, but for some reason it’s a growing one, and experts think obesity is one answer.
In the past 25 years, the number of cases in the United States climbed 26 percent, according to the largest study so far on the disease to date — on more than 2,500 American men with the disease. It was published Monday in the online version of Cancer, the American Cancer Society’s journal.
“We didn’t know before this that male breast cancer was increasing,” said study author Dr. Sharon Giordano, oncologist and assistant professor of medicine at the University of Texas’ M.D. Anderson Cancer Center in Houston. “It remains a very rare disease, even though it’s gone up.”
U.S. male breast cancer rates rose from 8.6 cases per 1 million men in the 1970s to 10.8 cases per 1 million in the 1990s. The study covered 1973-98. The increase was much smaller than that for women, who saw a 52 percent increase in breast cancer cases.
Fat produces estrogen
The study raises suspicion that obesity may be responsible for the breast cancer increase in both sexes, said Dr. Michael Thun, epidemiology chief at the Atlanta-based cancer society.
That’s because breast cancer has risen for men without the traditional reasons for the rise of female breast cancer, such as increased mammography and use of postmenopausal hormones such as estrogen, which has been linked to breast cancer.
But the waistlines of all Americans are growing. “Fat tissue produces estrogen,” which in turn can lead to breast cancer, said Thun, who was not involved in the latest study.
The study also found that men tended to be diagnosed with breast cancer later than women, likely because screening is not common. Men were slightly older — 67 compared to 62 for women — when the cancer was found, and the disease was typically in its later stages when discovered in men.
Despite this, cancer experts say the breast cancer risk for men remains low enough that they should be more concerned with common killers, such as heart disease and lung, prostate and colorectal cancers.
“When you have an increase in a rare cancer, you still have a rare cancer,” said Thun. “Given the rarity of disease, it’s far more important to have screening for colorectal cancer and to avoid smoking” than to focus on breast cancer in men.
Self-exams aren’t necessary for men. But if a man finds a lump in his breast, has nipple discharge or bleeding, he needs to see a doctor, Giordano said.