We investigated whether the use of chemotherapy before whole breast irradiation (WBI) using either conventional fractionation (CWBI) or hypofractionation (HWBI) is associated with increased toxic effects or worse cosmetic outcome compared with WBI alone.

We identified 6754 patients who received WBI alone (without a third field covering the superior axillary and supraclavicular nodal regions) with data prospectively collected in a statewide consortium. We reported rates of 4 toxic effects: physician-reported acute moist desquamation, patient-reported acute moderate/severe breast pain, a composite acute toxic effect measure (including moist desquamation and either patient- or physician-reported moderate/significant breast pain), and physician-reported impaired cosmetic outcome at 1 year after WBI. Successive multivariable models were constructed to estimate the effect of chemotherapy on these outcomes.

Rates of moist desquamation, patient-reported pain, composite acute toxic effects, and impaired cosmetic outcome were 23%, 34%, 42%, and 10% for 2859 patients receiving CWBI and 13%, 28%, 31%, and 11% for 3895 patients receiving HWBI. Receipt of chemotherapy before CWBI was not associated with higher rates of patient-reported pain, composite acute toxic effects, or impaired cosmetic outcome compared with CWBI without chemotherapy but was associated with more moist desquamation (odds ratio, 1.32 [1.07-1.63]; P = .01). Receipt of chemotherapy before HWBI was not associated with higher rates of any of the 4 toxic effects compared with HWBI alone.

In this cohort, use of chemotherapy before WBI was generally well tolerated. CWBI with chemotherapy but not HWBI with chemotherapy was associated with higher rates of moist desquamation. Rates of acute breast pain and impaired cosmetic outcome at 1 year were comparable in patients receiving chemotherapy before either CWBI or HWBI. These data support the use of HWBI after chemotherapy.