Comparison of Toxicity and Cosmetic Outcomes After Accelerated Partial Breast Irradiation or Whole Breast Irradiation Using 3-Dimensional Conformal External Beam Radiation Therapy

PURPOSE: To compare rates of acute and late skin toxicities and cosmetic outcomes after accelerated partial breast irradiation (APBI) or whole breast irradiation (WBI) using 3-dimensional conformal external beam radiation therapy in women with breast cancer after breast conservation surgery (BCS). METHODS AND MATERIALS: Women >35 years of age with invasive or noninvasive breast cancer ≤4 cm treated by BCS were randomized to 3D-CRT APBI (34 Gy/10 fractions/5 days) or WBI (40 Gy/16 fractions/3 weeks ± boost irradiation). The primary outcome was ipsilateral breast tumor recurrence. Important secondary outcomes were skin toxicities using Radiation Therapy Oncology Group scores, Late Effects Normal Tissue Task Force and Subjective, Objective, Management, Analytic scales, and adverse cosmetic outcome. This interim analysis focuses on the secondary endpoints of radiation toxicities and cosmesis. Patient and tumor characteristics and rates of adverse cosmetic outcomes and skin toxicities were compared using Fisher exact tests. All statistical tests were 2 sided, with P < .05 considered statistically significant. RESULTS: Between June 2011 and December 2015, 133 women with breast cancer were randomized to 3D-CRT APBI or WBI. Patient and tumor characteristics were balanced between the 2 arms. Median follow-up was 60 months (range, 12-93 months). Grade 4 late toxicity was not seen in either of the treatment arms, and grade 3 toxicity was very low for each endpoint assessed in both the groups. The rates of grade ≥2 acute dermatitis were 8% and 15%, respectively, for APBI and WBI (P = .18). Rates of grade ≥1 late radiation toxicities were higher in the WBI arm compared with the APBI arm for breast shrinkage (P = .008), pigmentation (P = .028), fibrosis (P = .040), induration (P = .048), and edema (P = .33). Adverse cosmesis at last follow-up was significantly higher in patients treated with WBI: 33% compared with 6% with APBI (P < .001). CONCLUSIONS: In women with breast cancer after BCS, APBI was associated with better cosmetic outcome and fewer late radiation toxicities than WBI.