Male cancers raise women's breast risks.

Women with a mother or sister stricken with breast cancer run a higher-than-average risk of developing the disease themselves. A new study now puts a surprising twist on that well-known fact: Women should also look to male relatives for hints of a breast cancer threat.

In the United States this year, about 1,000 men will develop breast cancer and 300 will die of the disease. Investigators have tried to learn whether female relatives of men with breast cancer run a high risk of the illness, but the studies have yielded conflicting results.

David E. Anderson and Michael D. Badzioch of the University of Texas M.D. Anderson Cancer Center in Houston decided to take another look at the families of male breast cancer patients. They focused on 88 men admitted to M.D. Anderson Cancer Center from 1958 through 1989 with a diagnosis of breast cancer. The investigators contacted the patients or a family member to find out whether any of the patients' first-degree female relatives - mothers, sisters, or daughters - had breast cancer. They confirmed each reported cancer case by examining the medical records or contacting the family's physician. Next, they compared the observed number of breast cancer cases with the expected number by getting data from a tumor registry that records breast cancer rates in the general population. Their analysis revealed that . first-degree female relatives of male breast cancer patients run twice the expected risk of breast cancer.

The Texans also looked at the number of breast cancer cases recorded among the close female relatives of 186 female breast cancer patients. These relatives, too, faced double the expected risk of developing breast cancer, according to the team's report in the July 15 JOURNAL OF THE NATIONAL CANCER INSTITUTE.

The new findings suggest that physicians assessing the risk of breast cancer should ask women whether any of their close relatives -- male or female - have had breast cancer. Epidemiologist Karin A. Rosenblatt of the University of Illinois at Urbana-Champaign agrees, but notes that male breast cancer is so rare that such questions will only infrequently turn up an affected relative.

In the course of their study, Anderson and Badzioch also turned up an unexpected link between a family history of prostate cancer and the risk of breast cancer. They found that women faced a four-fold increased threat of breast cancer if a male family member had a history of prostate cancer.

Anderson believes physicians should ask women about a family history of prostate cancer, as it seems to substantially increase the odds of breast cancer. On the other hand, Louise A. Brinton of the National Cancer Institute in Bethesda, Md., argues that researchers must confirm this finding before doctors change the way they gauge women's breast cancer risk..

The research raises the possibility that a cancer-causing gene or genes run in some families, predisposing some people in the family to breast cancer and others to prostate cancer, Anderson says. He notes that scientists have yet to unravel the mechanisms underlying breast and prostate cancer. - K.A. Fackelrnann