New York, March 9 (IANS): Having a family history of prostate and breast cancer among first-degree relatives may increase a woman's risk of developing breast cancer, claims a study.

"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 two-fold increase in risk of breast cancer," said Jennifer L. Beebe-Dimmer of the Barbara Ann Karmanos Cancer Institute in the US.

Beebe-Dimmer studied 78,171 women who enrolled in the Women's Health Initiative Observational Study between 1993 and 1998, and were free of breast cancer at the start of the study.

During follow-up, which ended in 2009, a total of 3,506 breast cancer cases were diagnosed.

The researchers found that a family history of prostate cancer in first-degree relatives (fathers, brothers, and sons) was linked with a 14 percent increase in breast cancer risk for women, after adjusting for various patient factors.

In separate analyses examining the joint impact of both cancers, a family history of both breast and prostate cancer was linked with a 78 percent increase in breast cancer risk.

Risks associated with a family history of both breast and prostate cancer was higher among African-American women than white women.

"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," Beebe-Dimmer said.

The study appeared online in the journal CANCER.