Reirradiation Of Locoregional Disease In Breast Cancer

To report our institution’s experience with reirradiation (reRT) in the setting of locoregional recurrent breast cancer. Between 1999 and 2019, all breast cancer patients treated with repeat breast/chest wall RT at our institution. Physician-reported adverse events (AEs) were assessed using CTCAE version 5.0. Freedom from locoregional recurrence and from distant metastasis, and overall survival (OS) were calculated using the Kaplan-Meier method. 74 patients were identified, 21 were treated with protons and 53 with photons +/- electrons. Intent was curative in 44 and palliative in 30, with gross disease in 36. At time of reRT, 27 patients had multiple prior recurrences, 3 had pre-operative RT, 5 were treated BID, 19 had concurrent chemotherapy, and 16 had concurrent hyperthermia. Table 1 describes course details. Median total dose was 100.2 Gy (IQR: 93.7-110), median interval between RT courses was 70 mo. (IQR: 29-127), and median follow-up was 22 mo. (IQR: 9-42). Among curative pts, freedom from locoregional recurrence was 91.8% at 12 mo. and 85.4% at 24 mo., freedom from distant metastasis 71.6% at 12 mo. and 63.0% at 24 mo., and OS 95.2% at 12 mo. and 74.9% at 24. Among palliative pts, freedom from locoregional recurrence was 59.7% at 12 mo. and 52.2% at 24 mo., and OS 65.6% at 12 mo. and 48.3% at 24 mo. Acute toxicities included dermatitis grade 1 (45), grade 2 (23), grade 3 (7). Delayed grade 2 toxicities were chest wall and soft issue fibrosis (8), skin infection (5), decreased ROM (4), wound complication (3), brachial plexopathy (2), lymphedema (2), soft-tissue necrosis (1). Persistence, without worsening, of grade 2 toxicities present before reRT were lymphedema (7), decreased ROM (6), brachial plexopathy (4), chest wall fibrosis (4), heart failure (1). 2 patients had grade 3 skin necrosis – 1 had diffuse tumor vascular invasion, which was identified as a possible contributor and 1 had chest wall necrosis requiring flap-based closure 2 yrs after reRT. 1 patient had a chronic non-healing wound prior to reRT. 14 patients developed rib fracture at median time of 11 mo. (IQR: 7-31). 10 were identified only by imaging. There were no grade 4/5 AEs. Disease control outcomes with curative intent reirradiation for locoregionally recurrent breast cancer appear promising, with acceptable acute and late toxicity. Additional follow-up is ongoing.Abstract 2061; TableIntervention1st RT Course: # of Patients2nd RT Course: # of PatientsSurgeroWide local excision: 53Wide local excision: 17Mastectomy: 16Mastectomy: 22Biopsy only: 5Biopsy only: 35Radiation CourseMedian Dose and Fraction• 50 Gy (IQR: 50-50.4) in 1.8-2 Gy/day: 64 pts• 42.56 (IQR: 40.05-42.56) in 2.25-3 Gy/day: 7 pts• 34-38.5 Gy in 10 fractions BID: 3 pts• 50 Gy (IQR: 40-50) in 1.8-2 Gy/day: 48 pts• 40.05 Gy (IQR: 40.03-40.46) in 2.25-7.3 Gy/ day: 21 pts• 39.6-60 Gy BID in 1.2-3.7 Gy/day: 5 ptsBoost: Dose (IQR)10 Gy (n = 44; 10-13.65 Gy; 2 integrated)10 Gy (n = 8; 6.94-10 Gy; 2 integrated) Open table in a new tab