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Study examines risk factors for cancer in unaffected breast of breast cancer patients

January 26, 2009

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 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 a fairly drastic measure, some women may choose this option due to a variety of factors, such as advice from their physician, fear of another breast cancer diagnosis, desire for cosmetic symmetry and family history of breast or other cancers.

While most breast cancer patients would not experience any survival benefit from such a contralateral prophylactic mastectomy, 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.

From the prophylactic mastectomy specimen, the researchers found that twenty-five patients (5 percent) had contralateral breast cancer, and 82 patients (15 percent) had cells in the other breast that were abnormal and could signify higher risk for breast cancer development.

When the investigators looked for clinical features associated with contralateral breast cancer, they found three independent factors: when the cancer cells had certain histologic invasive characteristics; when the cancer was present in more than one quadrant of the breast; and when the patient had a 5-year Gail risk of 1.67 percent or greater. 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.

Also, women aged 50 years or older at the initial cancer diagnosis or who had additional moderate- to high-risk cells in their affected breast were likely to have abnormal cells in the other breast that could potentially develop into cancer.

American Cancer Society