Abstract P2-14-05: Patient rather than tumor factors predict contralateral prophylactic mastectomy for inflammatory breast cancer
Authors: Drapalik Lauren M. , Amin Amanda L. , Simpson Ashley , Rock Lisa , Freyvogel Mary , Shenk Robert , Miller Megan E. 
Published: March 2023

Introduction: Inflammatory breast cancer (IBC) is an aggressive form of breast cancer with best outcomes result-ing from trimodality therapy: neoadjuvant chemotherapy (NAC), modified radical mastectomy (MRM), and radiation (PMRT). Contralateral prophylactic mastectomy (CPM) is generally discour-aged at the time of MRM due to poor prognosis. Our aim was to identify factors associated with CPM for IBC and determine its relationship with overall survival (OS). Methods: The National Cancer Database was used to identify female patients with AJCC stage IIIC unilateral IBC (cT4d and inflammatory histology code) treated 2004-2018. Patients were stratified by mastec-tomy type: unilateral mastectomy (UM) was defined as MRM or simple mastectomy, and CPM was defined as UM + CPM. Logistic regression identified factors associated with mastectomy type, and multivariable proportional Cox hazards regression identified factors associated with OS. A subset analysis of patients receiving NAC compared complete pathologic response (pCR) between mastec-tomy groups. Results: Of the 2,837 patients with non-metastatic IBC, 2,013 (70.2%) underwent UM and 855 (29.8%) had CPM. The CPM group was significantly younger than the UM group (mean age 52 vs. 56.6 years, p=0.028), more frequently identified as Non-Hispanic White (79.7% vs. 70.1%, p&lt; 0.001), and had private insurance (66.9% vs. 55.6%, p&lt; 0.001). Nearly all patients received chemotherapy and over 80% were treated with NAC. Receipt of PMRT did not differ by mastectomy type (80% for UM and CPM). On multivariable logistic regression, patients age &lt; 40 were more likely to undergo CPM than UM (OR 3.7, 95% CI 1.61-8.5, p&lt; 0.002). Patients with age &gt;70, Hispanic ethnicity, and public insur-ance were significantly less likely to receive CPM (all p≤0.002). On multivariable Cox regression ad-justed for patient, tumor, and treatment factors, CPM was not associated with OS benefit (HR 0.86, 95% CI 0.73-1.02, p=0.08). Higher histologic grade, node-positive disease, and greater co-morbidity were associated with poorer OS, while receipt of chemotherapy and PMRT improved OS. In the subset of NAC patients, overall pCR did not differ significantly by mastectomy type (CPM 22.3%, UM 19.4%, p=0.26). When included in multivariable models, pCR rates were not predictive of CPM de-spite being associated with improved OS. Conclusion: Nearly 30% of IBC patients undergo CPM despite discouragement by guidelines. Demographic char-acteristics – particularly age &lt; 40 – predicted CPM, suggesting patient preferences and access to care affect surgical decisions. As expected, trimodality therapy and favorable NAC response im-proved oncologic outcomes, but CPM had no association with OS. While CPM may be chosen for risk reduction and symmetry, patients should be counseled that it does not improve survival for IBC.

Citation Format: Lauren M. Drapalik, Amanda L. Amin, Ashley Simpson, Lisa Rock, Mary Freyvogel, Robert Shenk, Megan E. Miller. Patient rather than tumor factors predict contralateral prophylactic mastectomy for inflammatory breast cancer [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P2-14-05.