Marginal Survival Benefit After Contralateral Prophylactic Mastectomy

Alexander Castellino

July 16, 2014

Women with cancer in one breast are increasingly opting to undergo contralateral prophylactic mastectomy (CPM), despite a lack of evidence that they will live significantly longer. Now a study shows that survival benefits in such women might be only marginal, depending on the type and stage of breast cancer.

The study, published online July 16 in the Journal of the National Cancer Institute, projects a gain in life expectancy of 0.13 to 0.59 years for women with stage I breast cancer and of 0.08 to 0.29 years for women with stage II breast cancer.

"Many women cite survival benefits as a reason for undertaking double mastectomy on receiving a diagnosis of unilateral breast cancer. After looking at several subgroups of women, we found less than a 1% survival benefit after 20 years for all groups," said senior researcher Todd M. Tuttle, MD, from the Department of Surgery at the University of Minnesota in Minneapolis.

He does not know if this study will have an impact on the increasing rates of CPM, but he told Medscape Medical News that he hopes the data will help physicians and women with unilateral breast cancer make informed decisions.

Although the survival benefits seen in this study are small, CPM might be a good decision for women with a family history of breast cancer or a genetic predisposition, write Stephen G. Pauker, MD, and Mohamed Alseiari, MD, from the Department of Medicine at Tufts Medical Center in Boston, in an accompanying editorial.

Modeling Study Determines Survival Benefits

The estimates of survival after CPM come from a model developed by Dr. Tuttle and colleagues.

Modeling studies can be used to determine long-term survival in women with unilateral breast cancer, with or without CPM, when randomized clinical trials are not feasible, Dr. Tuttle told Medscape Medical News. In fact, retrospective studies are biased toward CPM in younger healthier women, he explained.

The researchers compared simulated survival for women with newly diagnosed breast cancer in those who opted for CPM and those who did not.

Their model took into account risk for contralateral breast cancer, mortality from the contralateral breast cancer, and mortality from the original breast cancer. They used information from the Surveillance, Epidemiology, and End Results (SEER) registry and from large meta-analyses for their analysis.

Survival was projected for women on the basis of age (40, 50, or 60 years), stage of breast cancer (I or II), and estrogen-receptor (ER) status (negative or positive). Women with BRCA mutations were excluded from the model because BRCA mutations are associated with a high risk of developing breast cancer in the contralateral breast.

Gain in life expectancy was highest for 40-year-old women with stage I ER-negative breast cancer (0.59 years), and lowest for 60-year-old women with stage II ER-negative disease (0.10 years). The absolute 20-year survival benefit from CPM was less than 1%, regardless of age, breast cancer stage, and ER status.

For women with stage I breast cancer, the 20-year survival difference between CPM and no CPM ranged from 0.56% to 0.94%; for women with stage II disease, the difference ranged from 0.36% to 0.61%.

CPM was more beneficial for women with stage I than stage II disease. In addition, potential benefits were much smaller for older women "because they have relatively fewer years of remaining life expectancy," the researchers note.

The analysis showed that CPM will confer a life expectancy of less than 2 months in a 60-year-old woman and of less than 7 months in a 40-year-old woman. These results are in line with previous data showing that CPM might benefit a small subset of women.

Weighing the Risks and Advantages of CPM

The basic assumption made in this analysis is that CPM will improve survival by preventing the development of potentially fatal cancer in the contralateral breast. The researchers note that the current clinical management of early-stage breast cancer predicts an even lower rate for cancer developing in the contralateral breast than the ones used in their model.

Besides survival, there are other effects that women with unilateral breast cancer have to consider before opting CPM, such as cancer-related anxiety, cosmesis, self-image, and anxiety about developing contralateral breast cancer. These variables were not part of the model because such information was not available in the databases used, Dr. Tuttle told Medscape Medical News. Another variable not considered in the model — complication rate — can be as high as 20%, he said.

"The balance between harm and benefit depends on the patient's preferences and highlights the importance of capturing the patient's values and expectations before considering CPM," write Drs. Pauker and Alseiari.

"This is a strong study and well done," Dr. Pauker told Medscape Medical News. Regardless of the marginal effects of CPM on survival, it is important to talk to women about their preferences, he said.

Dr. Tuttle, Dr. Pauker, and Dr. Alseiari have disclosed no relevant financial relationships.

J Natl Can Inst. Published online July 16, 2014. Abstract, Editorial

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