Why Are Double Mastectomy Rates on the Rise?

From the National Cancer Institute:

New results from a population-based study show that about 75 percent of women diagnosed with cancer in one breast who chose to have a double mastectomy did so despite being at low risk of developing a new cancer in the unaffected (contralateral) breast. Greater degree of worry about cancer recurrence was associated with removing the breast not affected by cancer, known as contralateral prophylactic mastectomy (CPM).

Dr. Sarah Hawley of the University of Michigan presented the findings, from a patient survey and analysis of SEER cancer registry data, November 30 at the American Society of Clinical Oncology's (ASCO) Quality Care Symposium  in San Diego.

Only a small percentage of women diagnosed with breast cancer have clinical risk factors known to increase their chances of developing a new cancer in the unaffected breast—that is, mutations in theBRCA1 or BRCA2 genes and/or a strong family history of breast or ovarian cancer. Yet several studies, including a previous analysis of SEER data, show that rates of CPM among U.S. women with breast cancer are rising.

To investigate why women may choose CPM, Dr. Hawley and her colleagues surveyed roughly 1,500 ethnically and racially diverse women diagnosed with breast cancer that had been reported to the Detroit and Los Angeles SEER registries. Of the 564 women who received mastectomies, 107 had CPM. The remaining women had breast conserving surgery.

When the researchers compared survey responses in the two groups of women, they found that those who reported being "very worried" about recurrence were about twice as likely to have CPM as those who reported being "somewhat worried" or "not at all worried."

In addition, women who reported that they had tested positive for BRCA1 or BRCA2 mutations were about 10 times more likely to undergo CPM than those who did not have a mutation, and those having two or more first-degree relatives with breast cancer were about 4.5 times more likely to undergo CPM than those who did not have a strong family history of the disease. Although CPM reduces the risk of developing a new cancer in the unaffected breast for women with these clinical risk factors, the procedure has not been shown to reduce the risk of a recurrence of the original cancer.

"Our results suggest that many women are choosing a double mastectomy who really don't need it," Dr. Hawley said. "We want to make sure that women choose CPM…with a good, clear understanding of what it's doing and not doing in terms of risks and benefits…. What you do is a personal decision, but it should be an informed one."

Dr. Hawley and her colleagues are still analyzing the survey data and have not yet examined some other possible reasons that women may be opting for CPM.

"This study suggests that we should re-examine how we communicate with our patients regarding the decision of whether to undergo prophylactic mastectomy," said Dr. Jyoti Patel, an oncologist at Northwestern University who moderated a November 30 ASCO press briefing at the symposium.

This study was funded by NCI (CA088370 and CA109696).

Further reading: "Preventive Double Mastectomies Increasing Despite Some Concerns"