By Christina Frangou

A population-based study has found that nearly three-fourths of women who undergo contralateral prophylactic mastectomy (CPM) following a breast cancer diagnosis do so despite having a very low clinical risk for contralateral disease.

The analysis of data in the Surveillance, Epidemiology and End Results program (SEER) showed that less than one-fourth of women who underwent CPM had a known mutation in the BRCA1 or BRCA2 gene and/or a strong family history of breast cancer. The Society for Surgical Oncology recommends CPM for patients who meet either criterion.

“Yet, many of the women who received CPM did not have any of these indications,” said lead author Sarah Hawley, PhD, associate professor of internal medicine at the University of Michigan Medical School, in Ann Arbor. She presented the findings at the American Society of Clinical Oncology’s 2012 Quality Care Symposium.

AT A GLANCE

Three-fourths of women who undergo CPM have a very low clinical risk for contralateral disease.

Women were more heavily influenced by worry about recurrence of breast cancer than by their true risk for recurrence

Although CPM reduces the risk for developing a new primary cancer in the unaffected breast, it has not been shown to reduce the risk for a recurrence of the original cancer.

Women were more heavily influenced by worry about recurrence of breast cancer than by their true risk for recurrence, she said. Women who said they were “very worried” about recurrence were almost twice as likely to have CPM as those who reported being “somewhat worried” or “not at all” worried.

CPM has not been shown to reduce the risk for a recurrence of the original cancer. The procedure reduces the risk for developing a new primary cancer in the unaffected breast, which is of great benefit to women with a high genetic risk for breast cancer but has no known clinical benefit for women without this risk. Despite this, a number of recent reports have shown that more and more women are choosing to undergo CPM. At Memorial Sloan-Kettering Cancer Center, for instance, the rate of undergoing the procedure increased threefold over an eight-year period, from 6.7% in 1997 to 24% in 2005 (J Clin Oncol 2011;29:2158-2164).

The reasons for the increase remain unclear. In a study published last year in the Journal of Clinical Oncology, researchers said that women may be influenced by a fear of recurrence, reluctance to undergo repeat biopsies and a desire for breast symmetry (J Clin Oncol 2011;29:2158-2164).

The guidelines of the National Comprehensive Cancer Network (NCCN) discourage CPM for most women and recommend that it be considered only on a case-by-case basis for women at high risk for breast cancer, such as those who carry a BRCA1 or BRCA2 mutation, or those with Li-Fraumeni syndrome who have a higher risk for contralateral breast cancer. According to information compiled by the breast cancer organization, Susan G. Komen for the Cure, only about 5% to 10% of breast cancer cases are related to a genetic mutation, a rate far lower than the current rate of CPM use.

In the SEER study, investigators surveyed 1,446 women diagnosed with breast cancer who reported to the Detroit and Los Angeles SEER registries between 2005 and 2007. All the women underwent follow-up surveys within four years of their original diagnosis.

Of 564 women who underwent mastectomies, 107 ultimately had CPM. The remaining women had breast-conserving surgery. Overall, 35% of women initially considered having CPM and 7% ultimately had the surgery. As expected, CPM rates were higher among women who underwent mastectomy: 53% contemplated having the double mastectomy and 19% eventually had the surgery.

Jyoti Patel, MD, an oncologist and assistant professor of medicine at Northwestern University’s Feinberg School of Medicine, Chicago, said the findings suggest that physicians may not be adequately educating patients about their risk for recurrent disease.

“Many women who overestimate their risk for developing breast cancer in the contralateral breast undergo unnecessary surgery. This study suggests that we reexamine how we communicate with our patients regarding the decision to undergo prophylactic mastectomy.”

Women who met the clinical criteria for CPM were the most likely to undergo the procedure, according to the study. Women who reported that they had tested positive for BRCA1 or BRCA2 gene mutations were about 10 times more likely to undergo CPM than patients without a positive genetic test result (odds ratio [OR], 10.61; 95% confidence interval [CI], 2.51-44.82). Women who had two or more first-degree relatives with breast cancer were about 4.5 times more likely to undergo CPM (OR, 4.40; 95% CI, 1.52-12.71).

This study is one of the largest population-based investigations with a significant ethnic and racial sample that takes into account patient attitudes and the strength of family history, Dr. Hawley said.