This study reported early toxicity and cosmetic outcomes of 21 patients treated with breast-conserving surgery and adjuvant PBT. Grade 2 and 3 dermatitis occurred in 62% and 14% of patients. Grade 2 and 3 pain was reported by 33% and 10% of patients. Median follow-up at the time of cosmetic evaluation was 27 months. Four patients (21%) reported fair cosmetic outcome and 15 patients (79%) reported good or excellent cosmetic outcome. No poor cosmesis was reported.