Stereotactic body radiation therapy (SBRT) for the treatment of primary breast cancer in patients not undergoing surgery.

ABSTRACT

PURPOSE: The purpose was to explore the role of stereotactic body radiation therapy (SBRT) in providing local control (LC) for primary breast cancer in patients unable to undergo surgery. MATERIALS/METHODS: Between 2015 and 2019, 13 non-surgical candidates with 14 lesions were treated with SBRT for primary breast cancer. In 4 cases, SBRT was used after whole breast radiation therapy (WBRT; 40-50 Gy/20-25 fractions). SBRT dose was 30-40 â€‹Gy in 5 fractions for patients treated with SBRT alone and 25-32 â€‹Gy in 4-5 fractions for those treated with SBRT â€‹+ â€‹WBRT. LC and overall survival (OS) were estimated using Kaplan-Meier curves. Response was also assessed using RECIST guidelines. RESULTS: Median follow-up was 32 (range 3.4-70.4) months. Imaging at median 2.2 (0.6-8.1) months post-SBRT showed median 43.2 â€‹% (range 2-100 â€‹%) decrease in the largest diameter and median 68.7 â€‹% (range 27.9-100 â€‹%) SUV reduction. There were 3 cases of local progression at 8.7-10.6 months. Estimated LC was 100 â€‹% at 6 months and 71.6 â€‹% at 12, 24 and 36 months. Estimated median OS was 100 â€‹% at 6 months, 76.9 â€‹% at 12 months, and 61.5 â€‹% at 24 and 36 months. Acute toxicity (n â€‹= â€‹13; 92.9 â€‹%) included grade (G)1 (n â€‹= â€‹8), G2 (n â€‹= â€‹4), and G4 (necrosis; n â€‹= â€‹1). Late toxicity included G2 edema (n â€‹= â€‹1) and G4 necrosis (n â€‹= â€‹2, including 1 consequential late effect). Only patients treated with SBRT â€‹+ â€‹WBRT experienced acute/late G4 toxicity, managed with resection or steroids. CONCLUSIONS: SBRT to primary breast cancer resulted in good LC in non-surgical/metastatic patients. Although necrosis (n â€‹= â€‹2) occurred in the SBRT â€‹+ â€‹WBRT group, it was successfully salvaged.