Financial Toxicity of Shorter Versus Longer Partial Breast Irradiation: A Randomized Clinical Trial.

Abstract

Within a randomized clinical trial comparing partial breast irradiation (PBI) dosing schedules, we sought to determine if shortening the radiation course would reduce financial toxicity (FT). In a phase III trial of 778 women age≥40 years who underwent segmental mastectomy for early breast cancer at 12 US cancer centers, patients were randomized 1:1 to external beam PBI using 15-22 fractions (control, n=385) versus 5-13 fractions (experimental, n=393) (NCT03077841). FT was assessed using comprehensive, multi-item instruments and scored using the Economic Strain and Resilience in Cancer (ENRICh) measure at baseline, end of radiation treatment (EoT), and 6- and 18-months post-radiation on a scale of 0 to 100 (higher score indicated worse FT). Mixed linear multivariable regression estimated adjusted difference-in-difference between EoT versus baseline FT by treatment arm. Minimal important difference (MID) in ENRICh score from baseline to EoT was estimated, anchored on change in patient-reported overall financial situation during that interval. Treatment arms had balanced clinical and sociodemographic characteristics. Median PBI duration was 22 days (interquartile range [IQR] 21-25) for the control arm versus 7 days (IQR 5-10) for the experimental arm (P<0.001). FT measures were completed for 96.1% of baseline and EoT assessments (n=1496/1556). Adjusted improvement in FT score between baseline to EoT was -2.0 (95% CI -3.6 to -0.4; P=0.02) for the experimental versus control arm. Of 52 individual FT items assessed, 9 favored the experimental arm at EoT (P<0.05), whereas none favored the control arm. MID in ENRICh score was 2.2 (95% CI 1.0-3.4). For early breast cancer patients eligible for PBI, shortening radiation duration by an average of 15 days yielded a reduction in end of treatment FT that was less than the MID estimated in this study.