Dosimetric predictors of toxicity and cosmesis in women treated with hypofractionated whole-breast irradiation.

77 Background: Large breast volume (BV) and distance of separation (DoS) have historically served as exclusionary criteria for hypofractionated whole breast irradiation (H-WBI). We investigate dosimetric parameters impacting toxicity and cosmesis. Methods: 299 consecutive patients with T0-2,N0-1,M0 breast cancer were treated with H-WBI at a single institution from 2007-2013. 4,256 cGy were delivered in 16 fractions via tangent photon beams utilizing inverse planning, with objectives to limit the V105 to 15%, the V110 to 2%, and the V115% to <0.1%. 227 patients with available treatment planning information and at least 6 months of follow-up (FU) were analyzed. Dosimetric parameters were correlated with acute (≤6 months post-treatment) and chronic toxicity and overall cosmesis. Proportions of toxicity grade and cosmesis score were compared with chi-square or Fisher exact tests. Results: With a median FU of 2.7 years (range 0.4-6.6 years), there were no local or regional recurrences, 1 distant failure, and o...