Abstract P5-10-04: Trimodal Therapy is Associated with Higher Overall Survival than Chemotherapy only in Patients with Metastatic Inflammatory Breast Cancer

Abstract Background: Metastatic inflammatory breast cancer (MIBC) is a rare and aggressive breast cancer with poor overall survival. Current standard of care treatment of MIBC consists of systemic therapy only with locoregional therapy to the primary site (surgery and radiation) utilized inconsistently and generally reserved for palliation. The purpose of this study is to examine overall survival (OS) among MIBC patients receiving chemotherapy only versus trimodal therapy in the National Cancer Database (NCDB). Patients and Methods: All patients diagnosed with MIBC from 2004 to 2021 were identified in the NCDB. The cohort was divided into a chemotherapy only group versus trimodal therapy. Trimodal therapy included chemotherapy, modified radical mastectomy, and radiation therapy. Radiation therapy included radiation to the breast, chest wall, and/or regional lymph nodes. We fitted Overlap Propensity Score Weighting (OPSW) Cox proportional hazard models to account for confounding in the relationship between OS and trimodal therapy status. Variables included in the propensity score model included age, Charlson-Deyo score, molecular subtype, and metastatic site. Results: A total of 4258 patients with MIBC were included in this study, of whom 1029 (24.17%) underwent trimodal therapy and 3229 (75.83%) received chemotherapy-only. Patients in the trimodal therapy group were younger (median age 54 vs. 59 years old; p<0.0001) compared to the chemotherapy-only group. Additionally, a higher percentage of patients in the trimodal therapy group had a Charlson Deyo Score of 0 (87.66% vs 82.25%, p-value<0.0001), held private insurance (58.16% vs 41.64%, p-value<0.0001), had a median income of $74,063 or higher (31.20% vs 27.50%, p-value=0.0109) and had less than 2 metastatic sites (90.43% vs 67.19%). There were no statistically significant differences in cancer subtypes between the treatment groups (p=0.158). On multivariable analysis, patients who underwent trimodal therapy were at 48% lower hazard of mortality compared to those on chemotherapy only (aHR: 0.52, 95% CI: 0.46-0.58, p<0.0001). Moreover, the median OS for those who received trimodal therapy was 49.5 months compared to 21.7 months (p<0.0001) for those who received chemotherapy only. Conclusions: In this cohort of patients with MIBC in the NCDB, trimodal therapy improves overall survival compared to chemotherapy only. Future prospective studies with patient-reported outcomes are needed to confirm these findings. Citation Format: Eric Schupp, Yevgeniya Goukun, Jacob Eckstein, Daniel Stover, Sachin Jhawar, Dionisia Quiroga, Margaret Gatti-Mays, Mathew Cherian, Min-Jeong Cho, Kai Johnson, Heather LeFebvre, JC Chen, Mohamed I Elsaid, Samilia Obeng-Gyasi. Trimodal Therapy is Associated with Higher Overall Survival than Chemotherapy only in Patients with Metastatic Inflammatory Breast Cancer [abstract]. In: Proceedings of the San Antonio Breast Cancer Symposium 2024; 2024 Dec 10-13; San Antonio, TX. Philadelphia (PA): AACR; Clin Cancer Res 2025;31(12 Suppl):Abstract nr P5-10-04.