New conventions.

Top Line: Is hypofractionated whole breast radiation with a hypofractionated boost safe and effective for Asian women? 

The Study: Ok, humor us for a moment. Most of the data comparing hypofractionated (HFRT) and conventionally fractionated whole breast radiation (CFRT) comes from North American and European trials. But uptake of HFRT in China (as in the US) has been relatively slow. In this trial, 734 Chinese women with early stage breast cancer receiving adjuvant whole breast radiation and lumpectomy boost were randomized to HFRT or CFRT. Though the trial allowed node positive disease and regional nodal irradiation (RNI), >80% of patients were T1, N0, and ER+, and <5% actually received RNI. Median age was much lower than in western studies (46 years !?), and 65% received chemotherapy. The CFRT regimen was 50 Gy in 25 fractions with 10 Gy in 5 fractions boost. The HFRT arm, similar to the previously published Chinese PMRT trial, was 43.5 Gy in 15 fraction with an 8.7 Gy in 3 fractions boost. The HFRT dose was estimated to be biologically equivalent to 50/25+10/5 using a breast cancer alpha/beta of 4.0. At 5 years, there was no difference in the cumulative incidence of local recurrence with HFRT compared to CFRT (1.2 vs 2.0%)--although there were fewer than expected LR events at final analysis. There was also no difference in locoregional recurrence (3.1 vs 3.8%), disease-free survival, or overall survival. Once again, CFRT had a significantly higher rate of grade 2 skin toxicity compared to HFRT (2.5→ 6.9%) with no difference in long-term cosmesis or other toxicity.

TBL: Hypofractionated whole breast radiation with boost has similar treatment outcomes and less skin toxicity than conventionally fractionated radiation in Asian women early stage breast cancer. | Wang, J Clin Oncol 2020