Kong, Iwa

PURPOSE Patients with breast cancer requiring postmastectomy radiation therapy (PMRT) often desire breast reconstruction. Reconstructions can be adversely affected by PMRT, and fear of reconstruction complications has discouraged adoption of short-course radiation therapy used after lumpectomy. To fill the evidence gap, we conducted a noninferiority trial of hypofractionated versus conventional PMRT in patients undergoing breast reconstruction. The primary outcome was reconstruction complication rate, a composite of wound healing, readmission, capsular contracture, unplanned reoperation, and reconstruction failure. METHODS Women with unilateral invasive breast cancer with planned immediate or delayed reconstruction and PMRT were randomly assigned (1:1) to 50 Gy (25 fractions/5 weeks) or 42.56 Gy (16 fractions/3 weeks). This study was designed with a noninferiority margin of 10%, assuming a 2-year reconstruction complication rate of 25% with conventional PMRT. Randomization was stratified by immediate versus delayed and autologous versus implant-only reconstruction. RESULTS Between 2018 and 2021, 898 patients enrolled with a median follow-up of 3.9 years; 825 patients were evaluable for the primary end point. The 24-month reconstruction complication rates were 12.3% (52/422) with hypofractionated PMRT and 10.2% (41/403) with conventional PMRT, corresponding to an estimated difference of -2.1% (95% CI, -6.5 to 2.2). The complication rate was higher (regardless of arm) with implant-only versus autologous reconstruction (odds ratio = 1.65). There was no statistically significant difference in 36-month locoregional recurrence rates: 1.5% (95% CI, 0.7 to 3.2) with hypofractionated and 2.2% (95% CI, 1.1 to 4.3) with conventional PMRT. Acute and late toxicity rates were not statistically different. CONCLUSION A 16-fraction course of hypofractionated PMRT is safe and noninferior to conventional PMRT in women undergoing breast reconstruction after mastectomy.