Abstract P2-11-02: Three-year outcomes with hypofractionated (HF) versus conventionally fractionated (CF) whole breast irradiation (WBI)

Abstract

Abstract Background: Adoption of HF-WBI remains low due in part to concerns regarding its safety when used with a tumor bed boost or in patients who have received chemotherapy or have large breast size. To address this, we conducted a randomized, multicenter trial to compare CF-WBI (50Gy/25fx+10-14Gy/5-7fx) to HF-WBI (42.56Gy/16fx+10-12.5Gy/4-5fx). Methods: From 2011 and 2014, 287 women with stage 0-II breast cancer, age ≥40 years, were randomized to CF-WBI or HF-WBI, stratified by chemotherapy and breast size. The primary outcome was the proportion of patients with adverse Breast Cancer Treatment Outcomes Scale (BCTOS) cosmetic score three years post-WBI, defined as a score of ≥2.5 (a score of 1 indicates no difference between the treated breast and contralateral breast, 2-slight difference, 3-moderate difference, 4-large difference). Secondary patient-reported outcomes included BCTOS functional status, BCTOS breast pain, Body Image Scale (BIS), and the FACT-B Trial Outcome Index (TOI). Additional secondary outcomes included photographically-assessed cosmesis scored by a 3-physician panel blinded to randomization arm using the RTOG scale, physician-assessed CTCAEv4.0, overall survival (OS), local recurrence-free survival (LRFS) and distant metastasis-free survival (DMFS). Chi-square, Fisher's exact, Wilcoxon's rank sum, logistic regression, and log-rank tests evaluated differences by treatment arm; survival was measured using the Kaplan-Meier method. All analyses were intention-to-treat. Results: Of 287 patients enrolled, 286 received the protocol-specified radiation dose. Thirty percent received chemotherapy (73% anthracycline, 92% taxane, 22% trastuzumab), 37% had large breast size (D cup or larger), and 44% were obese (BMI≥30). All baseline characteristics were well-balanced by treatment arm (P>0.05). Median follow-up is 4.1 years. For the primary outcome, adverse BCTOS cosmetic score at 3 years was noted in 13.6% (n=15/110) of CF-WBI and 8.2% (n=8/97) of HF-WBI patients (P=0.22). There were trends for lower risk of adverse BCTOS cosmetic score with HF-WBI, compared to CF-WBI, among patients who did not receive chemotherapy (OR=0.25, 95%CI 0.06-1.03; Pinteraction=0.07) or with large breast size (OR=0.26, 95%CI 0.07-0.98; Pinteraction=0.08). There were no patient subgroups where risk of adverse BCTOS cosmetic outcome was significantly higher with HF-WBI compared to CF-WBI. For secondary outcomes, there was no difference by treatment arm for BCTOS functional status (P=0.83), BCTOS breast pain (P=0.69), BIS (P=0.45), or FACT-B TOI (P=0.79). Poor-fair cosmetic outcome at 3 years assessed by the 3-physician panel was noted in 28.8% of CF-WBI patients and 35.4% of HF-WBI patients (P=0.31). In total, 19% CF-WBI patients and 20% of HF-WBI patients had a grade 2-3 toxicity at the three-year evaluation, with no difference by treatment arm (P=0.84). Five-year OS, LRFS, and DMFS were 99%, 98%, and 99%, respectively, with no difference by treatment arm (P=0.68, 0.37, 0.62). Conclusions: Three years after WBI followed by a tumor bed boost, outcomes with HF and CF are similar. Tumor bed boost, modern chemotherapy, and large breast size do not appear to be clinically meaningful contraindications to HF-WBI. Citation Format: Shaitelman SF, Lei X, Thompson A, Schlembach P, Arzu I, Bloom ES, Buchholz DJ, Chronowski GM, Dvorak T, Grade EJ, Hoffman KE, Kelly P, Perkins GH, Reed V, Shah S, Stauder MC, Strom EA, Tereffe W, Woodward WA, Baumann D, Amaya D, Guerra W, Morrison M, Hortobagyi G, Hunt KK, Buchholz TA, Smith BD. Three-year outcomes with hypofractionated (HF) versus conventionally fractionated (CF) whole breast irradiation (WBI) [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P2-11-02.