Single preoperative radiation therapy with delayed surgery for low-risk breast cancer: Oncologic outcome, toxicity and cosmesis of the SPORT-DS phase I trial

• Published in: Radiotherapy and oncology 2024-11, Vol.200, p.110515, Article 110515
• Main Authors: Lavigne, Danny, Hijal, Tarek, Vavassis, Peter, Guilbert, Marie-Christine, Sideris, Lucas, Dubé, Pierre, Gervais, Mai-Kim, Leblanc, Guy, Dufresne, Michel-Pierre, Nguyen, David, Tiberi, David, Mahmoud, Dima, Yassa, Michael
• Format: Article
• Language: English
• Subjects: Breast cancer; Neoadjuvant radiotherapy; Partial breast irradiation; Preoperative radiotherapy; Stereotactic ablative radiotherapy; Stereotactic body radiotherapy
• ISSN: 0167-8140; 1879-0887; 1879-0887
• DOI: 10.1016/j.radonc.2024.110515

•Single-fraction partial breast irradiation, followed by surgery after 3 months, leads to a high rate of pathologic response.•A single dose of 20 Gy to the breast tumor is acutely well tolerated.•The 3-month preoperative interval is suboptimal for late toxicities and cosmesis. A novel approach using single-fraction preoperative partial breast irradiation (PBI) for low-risk breast cancer is under study. We sought to investigate the rate of pathologic response (pR), toxicities and cosmetic results related to this new treatment strategy. Women of 65 years or older with stage I unifocal luminal A breast cancer were eligible for inclusion in this phase I prospective trial. Patients received a single 20 Gy dose of PBI followed by breast-conserving surgery (BCS) 3 months later. The primary endpoint was the pR rate, and the secondary endpoints were radiation therapy-related toxicity and cosmetic results. Thirteen patients were treated, with a median age of 71. Eleven patients (84.6 %) had pR with a median residual cellularity of 1 % (range: 0–10 %). At median follow-up of 48.5 months, no recurrences or cancer-related deaths were recorded. Acute radiation therapy-related toxicity were limited to grade 1 dermatitis and breast pain. At the 1-year follow-up, there were one grade 2 fat necrosis and two grade 3 toxicities (wound infection and hematoma). Only grade 1 toxicities remained at 2 years, but one grade 2 toxicity (fibrosis/induration) developed by the 3-year follow-up. Three-year patient-reported cosmetic outcomes were good or excellent in 60 % of patients. Single-fraction preoperative PBI preceding BCS for low-risk breast cancer is feasible, relatively well tolerated and leads to a high level of pR. The 3-month interval after PBI seems to place surgery in a post-radiation inflammatory phase. Further delay between PBI and surgery could improve pR and cosmetic outcome. NCT03917498.