Most women who have double mastectomy don't need it, U-M study finds

About 70 percent of women who have both breasts removed following a breast cancer diagnosis do so despite a very low risk of facing cancer in the healthy breast, new research from the University of Michigan Comprehensive Cancer Center finds.

Recent studies have shown an increase in women with breast cancer choosing this more aggressive surgery, called contralateral prophylactic mastectomy, which raises the question of potential overtreatment among these patients.

The study found that 90 percent of women who had surgery to remove both breasts reported being very worried about the cancer recurring. But, a diagnosis of breast cancer in one breast does not increase the likelihood of breast cancer recurring in the other breast for most women.

"Women appear to be using worry over cancer recurrence to choose contralateral prophylactic mastectomy. This does not make sense, because having a non-affected breast removed will not reduce the risk of recurrence in the affected breast," says Sarah Hawley, Ph.D., associate professor of internal medicine at the U-M Medical School.

Hawley will present the findings Nov. 30 at the American Society of Clinical Oncology's Quality Care Symposium.

The study authors looked at 1,446 women who had been treated for breast cancer and who had not had a recurrence. They found that 7 percent of women had surgery to remove both breasts. Among women who had a mastectomy, nearly 1 in 5 had a double mastectomy.

In addition to asking about the type of treatment, researchers asked about clinical indications for double mastectomy, including the patients' family history of breast and ovarian cancer and the results of any genetic testing.

Women with a family history of two or more immediate family members (mother, sister, daughter) with breast or ovarian cancer or with a positive genetic test for mutations in the BRCA1 or BRCA2 genes may be advised to consider having both breasts removed, because they are at high risk of a new cancer developing in the other breast. But women without these indications are very unlikely to develop a second cancer in the healthy breast.

"For women who do not have a strong family history or a genetic finding, we would argue it's probably not appropriate to get the unaffected breast removed," says Hawley, who is also a research investigator at the Ann Arbor VA Center of Excellence in Clinical Care Management Research and a member of the U-M Institute for Healthcare Policy and Innovation.

A double mastectomy is a bigger operation that is associated with more complications and a more difficult recovery. Women might still need to undergo chemotherapy or radiation therapy after their surgery – treatments that are known to reduce the risk of cancer recurring – which could delay their recovery further.

The study suggests that concern about recurrence is one of the biggest factors driving the decision to have this surgery. Hawley says it's important to educate women better that a contralateral mastectomy will not reduce the risk of recurrence. She and her colleagues have recently received a large grant from the National Cancer Institute that will in part allow them to develop a decision tool to help guide women through breast cancer treatment choices.