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Prophylactic Mastectomy Reduces Risk of Contralateral Disease: Presented at SSO

By Carole Bullock

CHICAGO -- March 20, 2008 -- Women who undergo prophylactic mastectomy can significantly reduce their risk of developing a contralateral breast cancer, according to results of a 10-year retrospective analysis presented here at the Society of Surgical Oncology (SSO) 61st Annual Cancer Symposium.

The study found a 90% decreased risk of contralateral breast cancer (hazard ratio = 0.10; 95% confidence interval, 0.03-0.30) in women who chose to have a contralateral prophylactic mastectomy (CPM) to prevent a second breast cancer development, reported lead author Judy C. Boughey, MD, Assistant Professor of Surgery, Mayo Clinic, Rochester, Minnesota, in a poster presentation here on March 14.

Through more than 9,000 person-years of follow-up (median 10.3 years), the rate of second breast cancer development was 0.6% in the CPM cohort, and the rate was 6.7% in the total-mastectomy-only (TMO) cohort.

Breast cancer patients in the CPM group (n = 488) included those who had had therapeutic mastectomy at the Mayo Clinic between 1960 and 1993 for stage I or II breast cancer and had a family history of breast cancer; all underwent a therapeutic mastectomy and a CPM. In this group, 45% of the participants underwent a prophylactic subcutaneous mastectomy and 55% underwent a prophylactic total mastectomy.

The CPM group was compared with a cohort of 511 patients with unilateral breast cancer who underwent TMO.

The analysis adjusted for age at surgery, stage of disease, and year of surgery.

Adjustment for age at diagnosis, year of surgery, stage, and number of positive nodes had no effect on this estimate.

Additionally, adjustment for use of tamoxifen, chemotherapy, or prior history of oophorectomy did not change the results.

The prevalence of a positive family history in the TMO cohort was 36%, and 100% in the CPM cohort.

A total of 21 patients (4%) in the CPM cohort had a known deleterious mutation in the "breast cancer gene" BRCA1 or BRCA2; 1 patient developed a second primary breast cancer.

"Our study gives information that helps women make decisions," Dr. Boughey concluded in an interview.

This study was funded by the National Cancer Institute and the Department of Defense.

[Presentation title: Breast Cancer Risk Following Contralateral Prophylactic Mastectomy in High Risk Women With a Personal History of Breast Cancer. Abstract P36]

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