A retrospective analysis on safety and effectiveness of hypofractioned post-mastectomy radiotherapy

The data supporting hypofractionated post-mastectomy radiotherapy is limited. The purpose of this study is to present the experience from Tarnów of hypofractionated PMRT over 20 fractions with respect to toxicity and effectiveness. We delivered post-mastectomy radiotherapy at the dose of 45 Gy in 20 fractions to the chest wall and the draining regional lymph nodes. The primary outcome of interest was to ensure that the rate of grade 3 or greater toxicity from the hypofractionation, at any time point, was non-inferior to standard post-mastectomy radiotherapy. We conducted a retrospective analysis of 211 women with stages I-IV breast cancer. After a median follow-up of 30 months, there were four reported grade 3 toxicities, with grade 3 lymphedema being the most frequent (1.5%). There were 134 reported grade 2 toxicities, with grade 2 fatigue being the most frequent (18%). There were six instances of isolated locoregional (6 of 211; 2.8%). Three-year estimated local recurrence-free survival was 96.4% (95% CI 0.921-0.984). The 3-year estimated distant recurrence-free survival was 77.8% (95% CI 0.699-0.838). To our knowledge, the results presented here are the largest single institution experience of hypofractionated post-mastectomy radiotherapy published in the literature to date. Our fractionation scheme, 45 Gy in 20 fractions, seems to be safe and effective with low toxicity.