This is the first study to examine these trends on a national level. The authors caution that this aggressive strategy may be unnecessary since most patients will never develop cancer in the second breast, and since the risk of cancer spreading to other parts of the body is often higher than the risk that cancer will be found in the second breast. The study will be published online October 22 in the Journal of Clinical Oncology (JCO).

Although breast cancer is now often diagnosed at earlier stages, we're seeing more women having contralateral prophylactic mastectomy, even though there are very little data showing that this irreversible procedure improves overall survival, explained lead author Todd M. Tuttle, MD, chief of surgical oncology and associate professor of surgery at the University of Minnesota. We need to determine why this is occurring and use this information to help counsel women about the potential for less invasive options.

The researchers used the Surveillance, Epidemiology, and End Results database (which provides detailed information about cancer diagnosis and treatment for 16 areas in the United States) to review the treatment of patients with unilateral (one-sided) breast cancer diagnosed between 1998 and 2003. Among 152,755 women diagnosed with stage I, II or III breast cancer during this period, 59,460 underwent a single mastectomy; 4,969 other women who were candidates for a single mastectomy chose to have CPM as well. The CPM rate among those who were candidates for a single mastectomy rose from 4.2 percent in 1998 to 11 percent in 2003. Younger women, non-Hispanic whites and women with lobular breast cancers were more likely to have CPM.

Dr. Tuttle proposed several potential reasons for the increase in the rate of CPM. There is more public awareness of the genetics of breast cancer and more frequent testing for mutations in BRCA genes, which increase contralateral breast cancer risk (although this study did not examine patients' BRCA status). Moreover, less invasive mastectomy approaches and improved breast reconstruction techniques may persuade more women to have both breasts removed at the same time.

He also emphasized that women often make the decision to have CPM quickly and at a vulnerable time. Instead, women may benefit from treating just the known breast cancer first and thinking about other options later, after their treatment is completed.

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