Regional Nodal & Chest Wall Re-Irradiation in Locoregional Recurrent Breast Cancer

Summary: Despite significant advances in tri-modality therapy, a small proportion of patients receiving initial post-lumpectomy radiation or post-mastectomy radiation (RT) will develop locoregional recurrence (LRR), which presents a therapeutic challenge. However, data surrounding regional nodal (RN), and chest wall (CW) photon 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 acceptable in-field control. 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)/volumetric modulated arc RT (VMAT)/3D-conformal RT (3DCRT) for LRR disease 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 Kapan-Meier method. Wilcoxon rank-sum test was utilized to compare the time between iRT and re-RT and grade of acute skin toxicity (AST) or presence of late toxicity (LT). 41 patients with a 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/VMAT (97.56%) or 3DCRT (2.44%). Median time from iRT to re-RT was 56.4 months (IQR, 31.2-166.5 months). 12 patients (29.27%) had distant metastatic 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, and the 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) observed 3 months following re-RT. 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. Re-RT for LRR BC with IMRT/VMAT is well tolerated with a low rate of severe toxicities and acceptable local control. Mature follow-up, increased sample size and future prospective trials are needed to elucidate the overall therapeutic impact, toxicity profile and optimal dose/fractionation for re-irradiation. Alexander Crum, MD (Presenting Author) - The Ohio State University; Sasha Beyer (she/her/hers), MD, PhD (Co-Author) - The Ohio State University; Yevgeniya Gokun, MS (Co-Author) - The Ohio State University; Mariella A. Mestres-Villanueva, MS (Co-Author) - The Ohio State University; Sierra J. Daniel, MHA (Co-Author) - The Ohio State University; Erin Healy, MD (Co-Author) - University of California Irvine; Therese Andraos, MD (Co-Author) - The Ohio State University; Rebekah Young, MD (Co-Author) - The Ohio State University; Jacob Eckstein, MD (Co-Author) - The Ohio State University; Julia White, MD (Co-Author) - The University of Kansas; Sachin Jhawar, MD (Co-Author) - The Ohio State University; Jose Bazan, MD, MS (Co-Author) - City of Hope Comprehensive Cancer Center