ESTRO 2025 - Abstract Book

S593

Clinical - Breast

ESTRO 2025

3649

Digital Poster Regional Nodal & Chest Wall Re-Irradiation in Locoregional Recurrent Breast Cancer Alexander E Crum 1 , Sasha Beyer 1 , Yevgeniya Gokun 2 , Mariella Mestres-Villanueva1 1 , Sierra Daniel 1 , Erin Healy 3 , Therese Andraos 1 , Rebekah Young 1 , Jacob Eckstein 1 , Julia White 4 , Jose Bazan 5 1 Radiation Oncology, The Ohio State University Wexner Medical Center, Columbus, USA. 2 Center for Biostatistics, The Ohio State University Wexner Medical Center, Columbus, USA. 3 Radiation Oncology, University of California Irvine Medical Center, Orange, USA. 4 Radiation Oncology, University of Kansas Medical Center, Kansas City, USA. 5 Radiation Oncology, City of Hope Comprehensive Cancer Center, Duarte, USA Purpose/Objective: Data surrounding regional nodal (RN), and chest wall (CW) photon re-irradiation (re-RT) is sparse, limited by low incidence, lack of defined indications and protocols for management, and increased proton utilization. We hypothesized that photon re-RT results in acceptable low toxicities and in-field control. Material/Methods: Our database was queried for breast cancer (BC) patients with prior breast, RN and/or CW RT, who received RN and/or CW re-RT with intensity modulated RT (IMRT) for locoregional recurrence (LRR) from 2014-2024. Demographics, disease characteristics, initial RT (iRT)/re-RT details, toxicity and outcome were collected. Overall survival (OS), in-field progression-free survival (IFPFS), and distant recurrence (DR) progression-free survival (DRPFS) were calculated from the completion of re-RT using Kaplan-Meier method. Time between iRT and re-RT and grade of acute skin toxicity (AST) or presence of late toxicity (LT) were compared utilizing Wilcoxon rank-sum test. Results: 41 patients, median age of 60 years-old (IQR, 46-66 years-old), HR+/HER2- (34%), HER2+ (27%), and TN (39%) receptor status, received re-RT for LRR BC from 2014-2024 with IMRT. Median time from iRT to re-RT was 56.4 months (IQR, 31.2-166.5 months). 12 patients (29.27%) had distant disease at time of re-RT, and 6 cases (14.63%) received palliative RT for symptomatic recurrence. Median re-RT total dose was 50 Gy (IQR, 45-55 Gy), with the most common regimen being 45 Gy in 1.5 Gy/fx BID (58.54%). 21 patients (51.22%) received a median boost of 10 Gy (IQR, 9-14 Gy), and 12 patients (29.27%) received concurrent chemotherapy; 11 of which (91.67%) received capecitabine. Median follow-up was 41 months. 10 patients (24.39%) had IFR, and at 62.8 months IFPFS was 65% (95% CI: 43%- 81%). 21 patients (51.22%) had DR, and median DRPFS was 52.7 months. At last follow-up, 17 patients had died. Median OS was 77 months. 29 patients (70.73%) had grade 1 AST, 11 patients (26.83%) had grade 2 AST, and no AST ≥ grade 3 were observed. 14 patients (34.15%) displayed LT, with one grade 3 LT (wound dehiscence). No grade 4/5 LT were observed. Although there was a trend between decreased time interval between RT courses and increased risk of AST (p=0.8025) and LT (p=0.8582), this did not reach statistical significance. Conclusion: Re-RT for LRR BC with IMRT is well tolerated with a low rate of severe toxicities and acceptable local control. Mature follow-up, increased sample size and prospective trials are needed to elucidate the overall therapeutic impact and toxicity profile for re-RT.

Keywords: Re-irradiation, IMRT, Locoregional