Contralateral prophylactic mastectomy decision-making in the population-based iCanCare study of early-stage breast cancer patients.

177 Background: Contralateral prophylactic mastectomy (CPM) use is increasing in women who are not at increased risk of contralateral cancer development and will experience no survival benefit from the more morbid procedure. Little is known about treatment decision-making or provider interactions.

METHODS: We surveyed a weighted random sample of newly diagnosed patients with early-stage breast cancer who were treated in 2013-14, identified through the population-based SEER registries of Los Angeles and Georgia about 3 months after surgical treatment, and merged with SEER data (N=2632, RR=70%), to determine receipt of diagnostic tests and factors related to the decision about surgery (including knowledge and perceived physician recommendation).

RESULTS: Nearly half of 2,436 respondents with unilateral non-metastatic cancer considered CPM (25% strongly). Only 37% of those who considered CPM knew that it does not improve survival for all women with breast cancer (24% believed it does, 39% didn't know). Among women receiving CPM, 37% believed it generally improves survival. Ultimately, 1,464 (60%) received BCS and 972 (40%) mastectomy (of whom 438, or 18% overall, received CPM). On multivariable analysis, pts who received CPM were younger, more likely to be white, and more likely to have a family history, private rather than Medicaid insurance, and received MRI. Even among pts without a deleterious genetic mutation or family history in multiple relatives (2,303), 400 (17%) received CPM. CPM was uncommon among pts who reported that their surgeons recommended against it (2.0% [17/832]) but much higher among those who reported no surgeon recommendation regarding CPM (21.3% [229/1,077]), and among those who perceived their surgeons to have recommended it (55.4% [147/265]).

CONCLUSIONS: Many patients consider CPM, but knowledge is low. Use of CPM is substantial among patients without clinical indications but is low when patients report their surgeon recommended against it. In the context of shared decision-making, surgeon recommendations against CPM might help reduce potential overtreatment.