A new study identifies certain patient and tumor characteristics that may help indicate which breast cancer patients would be the most likely to benefit from preventive surgery to remove the unaffected breast. Published in the March 1, 2009 issue of the journal Cancer, a peer-reviewed journal of the American Cancer Society, the study could help patients with breast cancer make more informed treatment choices.

Women diagnosed with breast cancer are known to be at increased risk of developing breast cancer in the opposite breast, either at the time of diagnosis or some time in the future. Identifying which women are most at risk of cancer in the other breast could help patients decide whether to have preventive treatment, including mastectomy to remove the unaffected breast.

While most breast cancer patients would not experience any survival benefit from such a contralateral prophylactic mastectomy (CPM), it is difficult to determine which patients should consider the procedure. If physicians could predict which patients are at the highest risk of developing contralateral breast cancer and which are not, many patients could preserve their unaffected breast if desired.

To identify the factors that predict contralateral breast cancer, Dr. Kelly K. Hunt and colleagues at the University of Texas M. D. Anderson Cancer Center in Houston studied 542 patients who had breast cancer in one breast and who had both breasts removed between 2000 and 2007.

Out of this group, 435 patients had no abnormal pathology identified in the opposite breast, 25 patients (5 percent) had contralateral breast cancer identified at surgery, and 82 patients (15 percent) had atypical ductal hyperplasia, atypical lobular hyperplasia or lobular carcinoma in situ.

Further analysis revealed that a five-year Gail risk of 1.67 percent or greater, an invasive lobular histology, and multiple tumors in the original breast were all strong predictors for contralateral breast cancer. The Gail model is a breast cancer risk assessment tool used for women without a cancer diagnosis that takes into consideration a woman's medical history, age, race and other characteristics.

"We went from having very little information on the benefit of this procedure for individual patients to identifying three independent and significant risk factors," Hunt said. "Each provides valuable insight into how likely a woman is to develop the disease in her other breast and enables physicians to make an educated recommendation if a patient will potentially benefit from CPM."

"We've always known contralateral breast cancer risk is not the same for all women and it is unnecessary to perform preventive mastectomies routinely. As we begin to clarify the specific risk factors, the number of women undergoing CPM may decrease and those with a low to moderate-risk may be more open to less extreme options for risk reduction, such as hormonal therapy and newer agents for prevention of breast cancer."

In addition to Hunt, other M. D. Anderson researchers contributing to this study include Min Yi, M.D., Funda Meric-Bernstam, M.D., Isabelle Bedrosian, M.D., Gildy V. Babiera, M.D., Rosa F. Hwang, M.D., Henry Kruerer, M.D., all in the Department of Surgical Oncology; Lavinia P. Middleton, M.D., in the Department of Pathology; Banu K. Arun, M.D., in the Department of Breast Medical Oncology; and Wei Yang, M.D., in the Department of Diagnostic Imaging.