Abstract P6-08-04: National trends in mastectomy for operable breast cancers treated with neoadjuvant chemotherapy

Abstract

Objective: Although neoadjuvant chemotherapy (NAC) has not been shown to improve survival compared with adjuvant therapy for patients with operable invasive breast cancer (IBC), it is often used to allow more limited surgery in the breast and axilla without compromising local control. We sought to evaluate national trends in mastectomy among patients with operable breast cancer treated with NAC and to characterize the contribution of demographic and tumor characteristics to changing trends. Methods: We queried the National Cancer Database (NCDB) 2014 Participant User File for adult women who underwent surgery and received chemotherapy for unilateral T1-3N0-3M0 IBC diagnosed between 2010 and 2014. Surgery was classified as lumpectomy (BCS), unilateral mastectomy (UM) or bilateral mastectomy (BM). Molecular subtype was categorized according to ER, PR, and HER2 status. We used logistic regression to model surgery use (BM or UM vs BCS), adjusting for the following clinical covariates that were selected a priori: age, race/ethnicity, year of diagnosis, comorbidity score, metropolitan vs urban/rural residence, patient distance from treating facility, % with less than high school education (zip code based), insurance type, clinical stage, histology, and molecular subtype. As those who achieved pathologic complete response (pCR) after NAC should be ideal candidates for BCS, we also looked at this group separately. We then performed sensitivity analyses further controlling for region of the country and facility type, and for facility. Results: We identified 235,339 patients who fulfilled our inclusion criteria. Of these patients, 25.3% were treated with NAC. Rates of pCR increased from 33.3% in 2010 to 46.3% in 2014 (p<0.001). Rates of BCS increased from 37.0% in 2010 to 40.8% in 2014 (p<0.001). While rates of UM decreased from 43.3% in 2010 to 34.7% in 2014 (p<0.001), rates of BM with or without reconstruction increased from 19.7% in 2010 to 24.6% in 2014 (p<0.001). Rates of BM without immediate reconstruction remained stable over time, from 11.8% in 2010 to 11.5% in 2014. Among patients who received NAC, factors that were independently associated with both UM and BM (versus BCS) for both the entire cohort and those who achieved pCR included younger age, greater patient distance from facility, and higher clinical stage. Factors that were inversely associated with both UM and BM included black race and ductal histology. More recent year of diagnosis was inversely associated with UM and directly associated with BM. Asian race was associated with UM while non-Hispanic white race was associated with BM. Private or managed care insurance and higher area education were also associated with BM. These results were materially unchanged in sensitivity analyses. Conclusion: Rates of pCR have increased over time among patients with operable IBC treated with NAC. While the rate of UM has declined over time, the rate of BM has increased. Significant sociodemographic differences exist between women who undergo BCS, and women who undergo UM and BM. Further study of factors that influence surgical decision-making in the NAC setting is warranted. Citation Format: Pollom E, Qian Y, Dirbas F, Horst K, Tsai CJ. National trends in mastectomy for operable breast cancers treated with neoadjuvant chemotherapy [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 P6-08-04.