For the study, the researchers analyzed data on more than 480,000 men who were among the male participants in Cancer Prevention Study II (CPS II). CPS II, a prospective mortality study of about 1.2 million Americans, was begun by the American Cancer Society in 1982.

After 12 years of follow-up, 3,141 cases of fatal prostate cancer were observed. After adjusting for other risk factors, the researchers found a small increased risk of fatal prostate cancer associated with a family history of breast cancer (in the absence of a family history of prostate cancer). According to the study, men younger than 65 years of age whose relative was diagnosed with breast cancer before age 50 had a 65 percent increased risk of fatal prostate cancer. Among Jewish men, family history of breast cancer increased risk of fatal prostate cancer by 73 percent; the increased risk for non-Jewish men was 13 percent. The researchers say the increased risks observed in Jewish men and younger men may reflect genetic alterations underlying familial clustering of prostate and breast cancer.

"An increased risk of breast cancer among women with relatives diagnosed with prostate cancer has been previously documented in several studies; our study, however, is only the second to document an increased risk of prostate cancer associated with a family history of breast cancer," says Carmen Rodriguez, MD, senior epidemiologist for the American Cancer Society and lead author of the study.

The current study has several strengths that support the credibility of its findings. First, the CPS-II study is prospective, meaning that information is gathered before cancer occurs, a technique which eliminated the possibility that a man's recollection of family history of cancer was triggered by their diagnosis with cancer. In addition, the study is large, and researchers were able to adjust their data for many known and possible prostate cancer risk factors.

"These results should be interpreted cautiously," says Dr. Rodriguez. "The findings from this study are limited to those cases of aggressive prostate cancer that result in death. The observed association, therefore, could reflect decreased prostate cancer survival among those with a positive family history rather than increased incidence."

"Although our results are consistent with a hereditable form of disease, a positive family history of breast cancer explains only one percent of all prostate cancer deaths in this group," adds Dr. Rodriguez. "Thus, our results suggest that family history of breast cancer explains a rather small proportion of the observed prostate cancer deaths."

Co-authors of the study include Eugenia E. Calle, PhD, Lilith M. Tatham, Phyllis A. Wingo, PhD, Heidi L. Miracle-McMahill, Michael J. Thun, MD, and Clark W. Heath, Jr., MD.

The American Cancer Society is the nationwide, community-based voluntary health organization dedicated to eliminating cancer as a major health problem by preventing cancer, saving lives and diminishing suffering from cancer, through research, education, advocacy, and service. For more information about cancer or the American Cancer Society and its programs, contact your local American Cancer Society by calling 1-800-ACS-2345.

Joann Schellenbach
National Director Media Relations
American Cancer Society
212-382-2169
jschelle@cancer.org