By Christina Frangou

Washington—Of the thousands of women with early-stage breast cancer in one breast who opt to undergo a contralateral prophylactic mastectomy every year, less than one in 100 will derive any survival benefit from the procedure, a new computer model suggests.

“We hope that by providing women with accurate and easily understood information about the potential benefits for contralateral prophylactic mastectomy [CPM], this may impact current trends,” said study co-author Pamela Portschy, MD, a surgical resident at the University of Minnesota, Minneapolis.

Dr. Portschy presented the findings at the 2013 Clinical Congress of the American College of Surgeons.

Rates of CPM have escalated over the past 20 years. Close to 20% of women in the United States today who have cancer in one breast undergo a double mastectomy, up from about 1% in the mid-1990s, said co-author Todd Tuttle, MD, chief of surgical oncology, University of Minnesota.

Experts attribute the rise in CPM to a number of factors such as increased use of magnetic resonance imaging, improved mastectomy and reconstruction techniques and greater awareness of genetic breast cancer and BRCA testing.

Previous studies also have shown that another key factor influencing a woman’s decision to undergo CPM is her substantial overestimation of the risks for contralateral breast cancer (Ann Intern Med 2013;159:373-381). One study from Dr. Tuttle and his colleagues reported that women without the BRCA mutation estimate their risk for developing a contralateral breast cancer (CBC) to be about 30% to 40% within a decade, which is the risk for women with the mutation. For women without the BRCA mutation, the risk is around 5% (Ann Surg Oncol 201;18:3129-3136).

Many breast cancer specialists have called for better tools to help inform women about their risks, especially in light of the publicity surrounding actress Angelina Jolie’s announcement that she underwent a preventive bilateral mastectomy. Ms. Jolie carries a mutated BRCA1 gene, putting her at very high risk for breast cancer.

Dr. Portschy and her colleagues set out to evaluate the survival benefit of CPM for women with unilateral early-stage breast cancer without a BRCA gene mutation. They developed a computer model that simulated a hypothetical cohort of women with stage I or II breast cancer to compare CPM with women who did not have a prophylactic operation to remove the second breast.

Gains in life expectancy with prophylactic mastectomy ranged from less than one month in a 60-year-old woman with estrogen receptor (ER)-positive, stage II breast cancer, to 6.3 months in a 40-year-old woman with ER-negative stage I disease.

The absolute overall difference in survival at 20 years ranged from 0.36% to 0.94% for both patient groups.

Cancer stage at diagnosis and ER status, not CPM, affected life expectancy, said Dr. Portschy.

“What we are trying to tell patients is that what is going to be potentially fatal is not a cancer that you may or may not get in the opposite breast. It’s whether or not this initial cancer has metastasized to your liver, lung or brain.”

The study adds to our knowledge about survival after CPM but is limited by methodological issues, said Isabelle Bedrosian, MD, associate professor of surgical oncology, the University of Texas MD Anderson Cancer Center, Houston. The study did not adjust for comorbid conditions, which must be factored in when counseling women about risk for breast cancer and overall survival, she said.

“If you are a healthy woman for whom there are no other health conditions, it may be worth considering a prophylactic mastectomy because your chance of dying of something unrelated to cancer is remote,” she said.

Dr. Bedrosian said that many of her patients without BRCA mutations who opt to undergo prophylactic mastectomy do so for peace of mind. “It’s anxiety, it’s fear. There is a great desire to do something to alleviate the fear and anxiety.”

She hopes that studies such as this will help raise awareness among the public about breast cancer risks. Many patients tell her in clinic that they understand that CPM offers no substantial survival benefit but they must contend with family and friends who want them to take every measure to prevent breast cancer in future.

“In order to move women away from this trend, we need to educate the community at large, not just our patients,” said Dr. Bedrosian.

For this study, authors analyzed data from the Early Breast Cancer Trialists’ Collaborative Group and the Surveillance, Epidemiology and End Results program. They examined the risk for developing CBC, dying from CBC, dying from primary breast cancer and the reduction in CBC due to CPM. The two databases include information on the treatment and survival of early breast cancer and include more than 100,000 women who have participated in randomized trials over the past 30 years in the United States.