Abstract P5-22-16: Choosing wisely recommendations against prophylactic bilateral mastectomy: Analysis of the National cancer database
Authors: Wallace AS , Threet A , Richman J , Lancaster R , Parker CC 
Published: February 2018

Abstract
Background: Surgical treatment for breast cancer is often a preference sensitive decision. The American Society of Breast Surgeons 2016 Choosing Wisely recommendation discourages routine contralateral prophylactic mastectomy (CPM). The purpose of this abstract is to analyze trends and factors that may be contributing to increasing utilization of CPM in the setting of unilateral breast cancer in the National Cancer Database (NCDB) from 2004-2013.
Methods: The NCDB is a national database of the American Cancer Society and the Commission on Cancer comprising approximately 70% of the cancer population in the US. Data from women with AJCC Stage 0-2 breast cancer treated with unilateral mastectomy (UM) vs CPM were abstracted. CPM was the primary outcome variable. Other variables included age, race, geographic region, payer status, income quartile, estrogen/progesterone receptor(ER/PR) status. HER2 status was not evaluated given limited availability of data. Categorical data was compared using Chi square tests. Odds ratios (OR) and Hazard ratios (HR) with confidence intervals (CI) were reported for univariate logistic regression models to evaluate effect of various factors on type of surgical treatment, and cox regression for survival with CPM, respectively. Significance was defined as p&lt;0.01.
Results: Median age for UM and CPM were 62.5 (SD 12) and 56.5 (SD 10.7) years respectively. In adjusted analysis, compared to Caucasian women, African American (OR 0.48, CI 0.47-0.50, p&lt;0.01) and Hispanic (OR 0.58, CI 0.56-0.61, p&lt;0.01) women were less likely to undergo CPM. Compared to women without insurance, those with private insurance (OR 1.53, CI 1.43-1.63, p&lt;0.01) or Medicare (OR 1.45, CI 1.37-1.57, p&lt;0.01) were more likely to under CPM. In comparison to women living in metro regions, those in urban (OR 1.08, CI 1.12-1.27, p&lt;0.01) and rural (OR 1.19, CI 1.12-1.27, p&lt;0.01) were more likely to undergo CPM. Women in the lower income quartile (OR 0.85 CI 0.82-0.87, p&lt;0.01) were less likely to undergo CPM compared to women in the highest quartile.
In the entire cohort, CPM was performed in 6.9% of ER/PR-, and 5.5% of ER/PR+ women (p&lt;0.01). ER/PR + women were less likely to undergo CPM (HR 0.7, CPM 0.69-0.73,p&lt; 0.01). Despite undergoing fewer CPM, women with ER/PR+ disease had improved overall survival in comparison to women who were ER/PR- There was an increase in utilization of CPM from 3.3% in 2004 to 7.5% in 2013 (p&lt;0.01) Progressive year of diagnosis (HR 1.12, CI 1.12-1.13, p&lt;0.01) was associated with increasing treatment with CPM, but among newly diagnosed women with CPM there was no change in survival over time (HR 1.0).
Conclusion: Women with newly diagnosed unilateral breast cancer are increasingly undergoing contralateral prophylactic mastectomy. There is great heterogeneity in socioeconomic factors associated with CPM. Women with ER/PR+ disease are undergoing CPM more often despite good outcomes in comparison to women with hormone negative disease. Given the new AJCC staging emphasis on tumor biology and disease outcomes, further research should consider socioeconomic variables as well as biology to create individualized risk assessment and decision aids to guide surgical decision making.
Citation Format: Wallace AS, Threet A, Richman J, Lancaster R, Parker CC. Choosing wisely recommendations against prophylactic bilateral mastectomy: Analysis of the National cancer database [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P5-22-16.