Abstract PS1-07-23: Outcome After Locoregional Recurrences For Definitively Treated Non-Metastatic Inflammatory Breast Cancer

Abstract Purpose: This study examines the clinical outcomes for Inflammatory Breast Cancer (IBC) patients who develop locoregional recurrence (LRR) after tri-modality therapy (TMT), including systemic therapy, modified radical mastectomy and post-mastectomy radiation therapy (PMRT). While LRR is uncommon after standard trimodal therapy targeting all pre-systemic therapy disease, we sought to characterize patient demographics, tumor characteristics, recurrence patterns, and survival outcomes after LRR in IBC. Methods: This data set was derived from patients enrolled in a prospective IBC registry diagnosed from 2010 to 2017. Among 140 M0 patients who had TMT, 9 with LRR were identified. Clinical data were extracted for the 9 patients with LRR using the Electronic Health Record. Descriptive statistics were used to summarize patient characteristics. ER/PR 10% was considered triple negative. Kaplan-Meier survival curves assessed time to LRR from the end of radiation and overall survival after LRR diagnosis. Results: The average age at diagnosis was 59 years (range 23-96 years). All patients were White. Six were not Hispanic or Latino, three were of unknown ethnicity. Four cancers were HR-HER2-, three were HR+HER2-, and two were HR-HER2+. All cancers were node-positive, four had N3 disease. The average time to LRR development after treatment was 17 months. Isolated LRR occurred in three cases. Two patients had LRR prior to and after radiation completion. One had palliative dose PMRT (30Gy/ 10 fractions) and progressed on the chest wall less than a month after PMRT. Another developed LRR approximately one month after radical mastectomy before radiation initiation, which was managed with surgical re-excision followed by completion of PMRT. A subsequent LRR occurred on the chest wall at 82 months. Overall survival after LRR was 14% at five years, with one patient alive without distant disease at 89 months. Chest wall recurrence was the most common LRR site, occurring in four of patients. Supraclavicular lymph node recurrence occurred in two patients, and axillary lymph node recurrence occurred in one patient. Conclusion: Low LRR among non-metastatic IBC patients after trimodality therapy has been previously reported ( 10% at 5 years). LRR occurred across molecular subtypes and was most often concurrent with distant disease, although isolated LRR did occur. We plan to analyze the radiation treatment plans and parameters to correlate radiation doses delivered to areas of recurrence, which may identify technical factors contributing to LRR development and inform future treatment optimization strategies. Citation Format: E. Onwubiko, M. Kai, M. Stauder, S. Sun, C. Goodman, A. Lucci, H. Johnson, R. Layman, W. Woodward, B. Lim, A. Nasrazadani, S. Saleem, V. Valero, G. Whitman, M. Patel, H. Le-Petross, Y. Lu, M. Alexander, A. Alexander, C. Yajima, L. Villarreal, H. Lopez. Outcome After Locoregional Recurrences For Definitively Treated Non-Metastatic Inflammatory Breast Cancer abstract. In: Proceedings of the San Antonio Breast Cancer Symposium 2025; 2025 Dec 9-12; San Antonio, TX. Philadelphia (PA): AACR; Clin Cancer Res 2026;32(4 Suppl):Abstract nr PS1-07-23.