Analysis of Outcomes Using Hypofractionated Tumor Bed Boost Combined With Hypofractionated Whole Breast Irradiation for Early-stage Breast Cancer.

INTRODUCTION: Tumor bed boost improves local control and is an important part of breast-conserving therapy. Data on the use of a hypofractioned tumor bed boost are needed. We performed a retrospective analysis of patients treated with hypofractionated whole breast irradiation (WBI) and hypofractionated boost to examine acute and delayed outcomes.

MATERIALS AND METHODS: We examined the records of patients treated with hypofractionated WBI and tumor bed boost after lumpectomy for Stage 0 to II breast cancer. Local control, toxicity, and cosmetic outcome were evaluated. Patient, tumor, and treatment characteristics were evaluated including excision volume, surgical technique, surgical complications, chemotherapy, endocrine therapy administration, radiation dose, fractionation, and technique.

RESULTS: A total of 143 patients received hypofractionated WBI with hypofractionated boost between 2010 and 2015. The median follow-up was 16.8 months. The median patient age was 65 years. Patient stage was 0, I, and II in 25%, 68%, and 7%, respectively. All patients received hypofractionated WBI with 42.5 Gy in 16 fractions. Sixty-one percent of women received a boost regimen of 2.66 Gy/fraction for 3 fractions. Boost techniques included noninvasive breast brachytherapy, electrons, 3-dimensional conformal radiation therapy, or a combination of techniques. Acute skin reaction was grade 1 in 65% and grade 2 in 32%. Good or excellent cosmetic outcome was achieved in 94% of patients. Subcutaneous fibrosis was the most common delayed toxicity in 19%, of which 86% was grade 1. There were no local recurrences.

CONCLUSIONS: Hypofractionated tumor bed boost is well-tolerated with a low rate of toxicity and high rate of good-to-excellent cosmetic outcome.