Abstract
BACKGROUND: Guidelines for partial breast irradiation as postoperative radiotherapy following breast-conserving therapy for breast cancer have been published; consequently, the National Comprehensive Cancer Network guidelines now designate accelerated partial breast irradiation (APBI) as a standard treatment option for these patients. APBI was introduced at our institution in July 2024. Here, we report the early clinical outcomes of the use of APBI and present a dosimetric comparison of volumetric modulated arc therapy (VMAT) and three-dimensional conformal radiotherapy (3D-CRT) in delivering APBI. METHODS: We performed a retrospective review of the charts of patients who underwent breast-conserving surgery followed by radiotherapy between July 2024 and May 2025. APBI was performed according to the ASTRO guidelines; specifically, 30 Gy was administered in 5 fractions every other day. Among patients receiving APBI, dosimetric parameters were compared between 3D-CRT and VMAT. Acute adverse events occurring within 28 days of treatment initiation were evaluated using the Common Terminology Criteria for Adverse Events, Version 5.0. RESULTS: Among the 268 patients, 109 were deemed suitable for APBI. Of these, 27 (25%) chose to undergo whole-breast irradiation, while 82 (75%) chose APBI. The median age in the APBI group was 56 years (range, 43–78). The pathologic tumor size was 2 cm or smaller in 63 patients and greater than 2 cm in 19 patients. Dosimetric parameter analysis revealed the superiority of VMAT over 3D-CRT in terms of target coverage and normal tissue sparing. Acute adverse events included grade 1 dermatitis in 65 (79%) patients and grade 1 breast pain in 4 (5%) patients; no grade 2 or worse events were reported. CONCLUSIONS: APBI with VMAT was completed without inducing severe acute toxicity in all the patients in this real-world setting. Long-term follow-up is needed to evaluate oncological outcomes and late toxicity.