Abstract P2-11-19: Safety and efficacy of re-irradiation for locoregional breast cancer recurrences using pulsed reduced dose rate technique and concurrent capecitabine

Purpose: Locoregionally recurrent breast cancer presents a tremendous therapeutic challenge, but successful treatment can provide a durable cure. Re-irradiation has been performed infrequently in the recurrent setting due to concern for toxicity. Pulsed reduced dose rate radiation is a technique that can decrease the toxicity of re-irradiation by increasing normal tissue repair. Here, we update our previously published results of chest wall re-irradiation with an additional 16 patients and a focus on outcomes and long term toxicities. Methods: Patients treated from 11/09/2000 to 04/21/2016 with pulsed reduced dose rate radiation therapy at the University of Wisconsin were identified by query of Aria radiation oncology record software. Patients were retreated to a median dose of 54 Gy (range 37.5-66 Gy) using pulsed reduced does rate technique, delivering radiation at an apparent dose rate of 0.067 Gy/min to allow for normal tissue repair. The median cumulative dose was 109.8 Gy (range 75 to 236 Gy). Eleven patients underwent comprehensive re-irradiation to the chest wall and locoregional lymphatics, while the remainder underwent re-treatment limited to the site of recurrence. Concurrent capecitabine was given to 15 patients, most frequently at 500mg BID (range 1000 mg to 1500mg daily). The Kaplan-Meier method was used for survival analysis. Results: Thirty-three patients were identified who were treated with pulsed reduced dose rate radiation therapy for locoregionally recurrent invasive breast cancer with a median follow-up of 19.8 months (range 6.8-133.8 months). Sixteen patients were treated with curative intent and 17 patients were treated with palliative intent. Twenty-two patients had gross disease present at the time of treatment, 6 patients had microscopically positive surgical margins, and 5 patients were treated who had negative margins. The 2 year locoregional recurrence free survival was 70.5% by the Kaplan-Meier method for all patients and 81.5% for patients treated with curative intent. Two year overall survival was 43.6% for all patients and 72.2% in patients treated with curative intent. The rate of acute grade 3 skin toxicity was 21.2%. No other acute grade three toxicities occurred. A total of 9 patients (27.2%) developed late grade 3 or greater toxicities, including 4 patients who developed lymphedema, 4 patients who developed non-healing wounds, and one patient who developed both lymphedema and a non-healing wound. Conclusion: Pulsed reduced dose rate radiation therapy with capecitabine is an effective method for treating patients with recurrent breast cancer. The moderate risk of toxicity is warranted in a subset of patients with high risk of disease recurrence or morbidity from disease progression. Further work, including prospective studies, is needed to determine the patients who who will benefit most from this technique. Citation Format: Burr A, Howard S. Safety and efficacy of re-irradiation for locoregional breast cancer recurrences using pulsed reduced dose rate technique and concurrent capecitabine [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P2-11-19.