Robotic Stereotactic Accelerated Partial-Breast Irradiation for Early-Stage Breast Cancer: 5-Year Results of a Single-Institution Pilot Study

Abstract

early stage breast cancer following breast conserving surgery. Patients who received chemotherapy (CHT) are not well represented on these trials. This study investigates whether receiving CHT prior to WBI is associated with increased toxicity or worse cosmetic outcomes. Materials/Methods: We identified 7,014 women in a statewide radiation oncology quality consortium database who received WBI with a surgical cavity boost between 11/2011 and 8/2018. Toxicity data were available for 6,870 patients. Significant acute toxicity was defined as patient-reported moderate/severe breast pain (4/10), physician-reported CTCAE grade 2 breast pain, or the development of moist desquamation between 7 days prior to and 42 days following the completion of radiotherapy. We determined rates of physician-reported fair/poor cosmetic outcome per the Harvard criteria in 2,012 patients who had 1 year of follow-up. Rates of significant acute toxicity and fair/poor cosmetic outcome were compared among patients receiving conventionally fractionated treatment (C-WBI) or H-WBI. Multivariable modeling, adjusting for age, race, BMI, breast volume, separation along the central axis, comorbidity index, smoking status, radiation planning technique, breast D50, triple negative breast cancer, pTis disease, treatment at an academic institution, and receipt of CHT, were used to quantify the strength of association, given as an odds ratio [95%CI], between patient or treatment related factors and clinical endpoints. Results: C-WBI and H-WBI most commonly comprised 45-50.4 Gy in 25-28 fractions and 40-42.72 Gy in 15-16 fractions, respectively. A boost of 10-16 Gy in 5-8 fractions and 10 in 4 fractions was most common for C-WBI and H-WBI, respectively. CHT was administered prior to radiation therapy in 1266 (35%) of the 3,628 patients who received C-WBI and in 558 (17%) of the 3,242 patients who received H-WBI. Crude rates of significant acute toxicity were 43% and 40% for patients receiving CHT followed by C-WBI and C-WBI without CHT, respectively, and 29% and 27% for patients receiving CHT followed by H-WBI and H-WBI without CHT, respectively. CHT was not associated with worse acute toxicity for patients receiving C-WBI (ORZ0.94 [0.79-1.12], pZ0.50) or H-WBI (ORZ0.79 [0.63-1.00], pZ0.054). CHT was not associated with increased rates of fair/poor cosmetic outcomes at 1 year (ORZ1.21 [0.82-1.78], pZ0.33), independent of fractionation. Conclusion: In this large, multi-center cohort, rates of significant acute toxicity and fair/poor cosmetic outcomes were not worse in patients receiving chemotherapy prior to whole breast irradiation, compared to patients who did not receive chemotherapy, regardless of fraction size.