(ChemotherapyAdvisor) – Most women who undergo contralateral prophylactic mastectomy (CPM) have a strong family history for breast or ovarian cancer, positive genetic tests, and worry about recurrence, yet are not expected to benefit in terms of disease-free survival because the procedure is not clinically indicated, according to a study released today in advance of ASCO’s inaugural 2012 Quality Care Symposium, to be held in San Diego, CA, November 30-December 1.

“The growing rate of CPM among women diagnosed with breast cancer has raised concerns about potential for over-treatment, yet little is known about factors that affect the decisions for this surgical treatment option,” noted Sarah T. Hawley, PhD, MPH, lead author and Associate Professor of General Medicine at University of Michigan, Ann Arbor, MI.

The investigators surveyed women newly diagnosed with breast cancer and reported to the Detroit and Los Angeles Surveillance Epidemiology and End Results registries from June 2005 to February 2007; this cohort was resurveyed approximately 4 years later. The women received lumpectomy, unilateral mastectomy, or CPM.

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Of the 1,446 women who had not had a recurrence of breast cancer by the time of the second survey, 35% had considered CPM and 7.4% underwent surgery. Among those who received a mastectomy for the affected breast, 53% considered CPM, and 19% received it.

“About 70% of patients who received CPM were clinically at very low risk for contralateral disease,” Dr. Hawley noted, adding that “90% of those who got CPM reported being very worried about recurrence when making their treatment decision, compared to 80% of those who received unilateral mastectomy (P<0.05).”

Multivariate regression showed receipt of CPM vs unilateral mastectomy was associated with having a family history (at least two first-degree relative with breast or ovarian cancer; OR 5.1; 95% CI 2.49–10.1) and/or a positive genetic test for alterations in BRCA1 and BRCA2 genes (OR 10.93; 95% CI 3.37–35.71), as well as greater worry about recurrence (OR 2.07; 95% CI 1.01–4.51).

“If worries about cancer recurrence are affecting a woman’s psychological wellbeing, perhaps CPM would be the right choice, but our results clearly show that too many women are undergoing unnecessary surgery,” said Dr. Hawley.

In the general population of women diagnosed with breast cancer, risk of developing a new cancer in the unaffected breast is <1%, whereas the risk of cancer recurring locally is 8%.

“Our findings also suggest that some women made the decision based on their misconception about the ability of CPM to reduce the risk of local recurrence of cancer. In everyday practice, this means that physicians need to understand the strong impact of worry about cancer recurrence in patient decision making, and may need to do a better job of educating and reassuring women about their true risks of both cancer recurrence and of developing a new cancer,” she added.

Next steps include a large study designed to explore how decisions about breast cancer treatments, including CPM, are made for patients who do not have an increased risk of cancer in the unaffected breast. The perspective of both physicians as well as patients will be included. Decision tools to help patients understand risks and benefits of various treatment options are also being developed.