Breast Cancer Risk Connected to Family History of Prostate Cancer

Women with a first-degree relative diagnosed with prostate cancer may be at increased risk for developing breast cancer, according to the results of a new study. The study authors suggest that clinicians should review a patient’s broad family history of cancer, not just the history of female relatives. The study results were published in the journal Cancer.

Among the 78,171 women enrolled in the Women’s Health Initiative (WHI) observational study, those with a first-degree relative diagnosed with prostate cancer had a 14% relative increased risk of being diagnosed with breast cancer. In a separate analysis, a history of both prostate and breast cancer among first-degree relatives was associated with a 78% relative increased risk of breast cancer. While a family history of prostate cancer was modestly predictive of breast cancer risk for both African American and white women, the association was statistically significant only for white women. African American women were at the greatest risk for breast cancer if they had first-degree relatives with both prostate and breast cancer.

“The increase in breast cancer risk associated with having a positive family history of prostate cancer is modest. However, women with a family history of both breast and prostate cancer among first-degree relatives have an almost twofold increase in risk of breast cancer,” said study author Jennifer L. Beebe-Dimmer, MPH, PhD, of the Karmanos Cancer Institute and Wayne State University School of Medicine in Detroit, in a statement.

“These findings are important in that they can be used to support an approach by clinicians to collect a complete family history of all cancers-particularly among first-degree relatives-in order to assess patient risk for developing cancer,” said Beebe-Dimmer. “Families with clustering of different tumors may be particularly important to study in order to discover new genetic mutations to explain this clustering.”

Beebe-Dimmer and colleagues examined the link between prostate cancer and breast cancer because family history of either disease has been shown to increase risk and because there may be genetic and environmental factors that contribute to both.

The WHI study enrolled healthy women aged 50 to 79 between 1993 and 1998. During the 11-year follow-up, a total of 3,506 breast cancers were diagnosed. Women diagnosed with breast cancer were more likely to have a history of benign breast disease, to have had a mammogram within the last 2 years, to be non-Hispanic white, to be college-educated, and to have a history of hormone therapy use. They were less likely to smoke, to have children, or to have had a hysterectomy. The median age at breast cancer diagnosis was 69.

Those diagnosed with breast cancer were also more likely to have had one or more relatives diagnosed with prostate cancer (11.6% vs 10.1% of women without a breast cancer diagnosis).

A family history of colorectal cancer marginally increased the risk of breast cancer by 8%, after adjusting for a family history of both breast and prostate cancer. Women who had first-degree relatives with breast, prostate, and colorectal cancer had about a twofold increase in the risk of breast cancer (hazard ratio, 2.06).

Further studies are needed to understand the strengths of these risk associations, as well as the genetics that may be contributing to the risk of both prostate and breast cancer.