Three-Year Outcomes With Hypofractionated Versus Conventionally Fractionated Whole-Breast Irradiation: Results of a Randomized, Noninferiority Clinical Trial

Abstract

Purpose: The adoption of hypofractionated whole-breast irradiation (HF-WBI) remains low, in part because of 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 conventionally fractionated whole-breast irradiation (CF-WBI; 50 Gy/25 fx + 10 to 14 Gy/5 to 7 fx) with HF-WBI (42.56 Gy/16 fx + 10 to 12.5 Gy/4 to 5 fx).

Patients and methods: From 2011 to 2014, 287 women with stage 0 to II breast cancer were randomly assigned to CF-WBI or HF-WBI, stratified by chemotherapy, margin status, cosmesis, and breast size. The trial was designed to test the hypothesis that HF-WBI is not inferior to CF-WBI with regard to the proportion of patients with adverse cosmetic outcome 3 years after radiation, assessed using the Breast Cancer Treatment Outcomes Scale. Secondary outcomes included photographically assessed cosmesis scored by a three-physician panel and local recurrence-free survival. Analyses were intention to treat.

Results: A total of 286 patients received the protocol-specified radiation dose, 30% received chemotherapy, and 36.9% had large breast size. Baseline characteristics were well balanced. Median follow-up was 4.1 years. Three-year adverse cosmetic outcome was 5.4% lower with HF-WBI ( P_{noninferiority} = .002; absolute risks were 8.2% [n = 8] with HF-WBI v 13.6% [n = 15] with CF-WBI). For those treated with chemotherapy, adverse cosmetic outcome was higher by 4.1% (90% upper confidence limit, 15.0%) with HF-WBI than with CF-WBI; for large breast size, adverse cosmetic outcome was 18.6% lower (90% upper confidence limit, -8.0%) with HF-WBI. Poor or fair photographically assessed cosmesis was noted in 28.8% of CF-WBI patients and 35.4% of HF-WBI patients ( P = .31). Three-year local recurrence-free survival was 99% with both HF-WBI and CF-WBI ( P = .37).

Conclusion: Three years after WBI followed by a tumor bed boost, outcomes with hypofractionation and conventional fractionation are similar. Tumor bed boost, chemotherapy, and larger breast size do not seem to be strong contraindications to HF-WBI.

Fig 1.

Consort diagram. BCTOS, Breast Cancer Treatment Outcomes Scale; BIS, Body Image Scale; CF-WBI, conventionally fractionated whole-breast irradiation; CT, computed tomography; HF-WBI, hypofractionated whole-breast irradiation; MD, physician; NCI CTCAE, National Cancer Institute Common Terminology Criteria for Adverse Events.

Fig 2.

Forest plot. Strata-specific analyses. The x-axis indicates the absolute difference in the percentage of patients with adverse cosmetic outcome (the primary outcome) among those treated with hypofractionated whole-breast irradiation (HF-WBI) minus those treated with conventionally fractionated whole-breast irradiation (CF-WBI). For example, the overall primary outcome was 8.2% with HF-WBI and 13.6% with CF-WBI, for a difference of 8.2%−13.6% = −5.4%, which is shown as the gold diamond for the overall effect size. The vertical line at 10% indicates the noninferiority margin, and the gold horizontal bars indicate the 90% upper confidence limit (UCL) for each difference. The top two rows of the graph refer to the baseline (postoperative, preradiation) physician-assessed cosmesis, which was one of the stratification factors. CF, conventional fractionation; HF, hypofractionation.

Fig A1.

Representative photographs for 3-year end points rated by the physician panel.