Comparative acute toxicity from whole breast irradiation using 3-week accelerated schedule with concomitant boost and the 6.5-week conventional schedule with sequential boost for early-stage breast cancer.

Background: We aimed to evaluate the incidence of acute toxicity in a 3-week accelerated radiation therapy (RT) schedule with a concomitant boost compared with the 6.5-week conventional schedule with a sequential boost for early-stage, node-negative breast cancer.

Materials And Methods: This study included the first 50 patients treated on protocol using the accelerated schedule as well as 74 patients with comparable stages of disease treated over the same period using the conventional schedule. An accelerated schedule of 40.5 Gy × 2.7 Gy/fraction to the whole breast with 4.5 Gy × 0.3 Gy/fraction concomitant boost, for a delivered total dose of 45.0 Gy × 3.0 Gy/fraction in 15 fractions to the lumpectomy site. The conventional schedule used 46.8 Gy × 1.8 Gy to the whole breast with a sequential boost of 14.0 Gy × 2.0 Gy/fraction, delivering a total dose of 60.8 Gy × 33 fractions to the lumpectomy site. The side effects observed during RT and through the initial 8 weeks after treatment were scored for acute toxicity.

Results: A lower incidence of ≥ grade 2 skin toxicity was observed among patients treated on the accelerated schedule compared with those treated on the conventional schedule (p = .0015). There was a higher incidence of breast pain among patients receiving the conventional schedule (p = .045). No significant difference in the incidence of breast edema, fatigue, or hematologic side effects was observed between the 2 groups.

Conclusion: Our observations suggest that there is acceptable toxicity with the accelerated schedule as used in this study. Further, it is not associated with a higher risk of acute toxicity when compared with the conventional schedule. Patients in the study are being followed, and clinical outcomes will be reported as the data mature.