Toxicity Profiles Following Whole Breast Irradiation plus Sequential Boost using Hypofractionated or Conventionally Fractionated Treatment

Abstract

To compare toxicity and cosmesis in women with early-stage breast cancer treated with conventionally fractionated (C-WB) or hypofractionated (H-WB) whole breast irradiation with sequential boost. We performed a matched-pair analysis to compare patients treated with C-WB or H-WB as part of BCT at a single institution from 2008-2016. 240 patients (120 pairs) were matched by age (+/- 3 y), T-stage, chemotherapy (y/n), and endocrine therapy (y/n). Acute (≤6 mos post-WB) and chronic (>6 mos post-WB) toxicities were graded according to CTCAEv3.0. Cosmesis was evaluated using the Harvard cosmesis scale. Outcomes were analyzed using t-tests for continuous variables, χ2 for categorical variables, and Kaplan-Meier estimates. P-values <0.05 were considered significant. Median whole breast dose was 42.56 Gy (39.9-41.72) in 2.66 Gy fractions for H-WB and 45 Gy (45-50.4) in 1.8-2 Gy fractions for C-WB. Median boost dose was 10.64 Gy (2.66-14) in 2.50-2.66 Gy fractions for H-WB and 16 Gy (6-22.5) in 2-2.5 Gy fractions for C-WB. Median follow up for all patients was 2.6y (0.1-28.1); 1.1 and 6.3y for H-WB and C-WB, respectively (p<0.001). Median age at diagnosis was 61 (44-88). 84% and 12% of patients received anti-hormone and chemotherapy, respectively. There were no differences in race, menopausal status, histology, or grade. The H-WB group had more close margins (< 2 mm; 32 v 4%, p<0.001). There were no differences in acute toxicity between H-WB and C-WB. Rates of grade 2/3 acute toxicity were <10% overall, with the exception of hyperpigmentation (15%). Rates of chronic toxicity (Table 1) were similar, with low rates of grade 2/3 toxicities (<12%). Cosmesis was good/excellent in 93% of patients, with no differences in the acute period. There were more H-WB patients with fair/poor chronic cosmesis (13 v 3%, p=0.026). Clinical outcomes were excellent at 3 years and similar between H-WB and C-WB. Patients had favorable toxicity profiles regardless of fractionation schedule used. In light of recently published data supporting favorable toxicity and cosmesis with hypofractionated regimens, we are evaluating specific dosimetric or patient related features that may contribute to the small difference in chronic cosmetic outcomes when comparing groups.Abstract 2034; Table 1ToxicityH-WBGrade 0/1 (No fat necrosis) N(%)H-WBGrade 2/3 (+ fat necrosis) N(%)C-WBGrade 0/1 (No fat necrosis) N(%)C-WBGrade 2/3 (+ fat necrosis) N(%)p-valueRadiation Dermatitis6 (100)0 (0)84 (99)1 (1)0.39Hyperpigmentation53 (87)9 (13)79 (92)7 (8)0.33Hypopigmentation61 (100)0 (0)84 (99)1 (1)0.39Breast Pain60 (97)2 (3)84 (99)1 (1)0.38Breast Edema48 (89)6 (11)71 (93)5 (7)0.36Telangiectasia61 (100)0 (0)86 (99)1 (1)0.40Induration/Fibrosis51 (84)10 (16)70 (91)8 (9)0.19Fat Necrosis57 (93)4 (7)80 (94)5 (6)0.87 Open table in a new tab