Comparison of Acute and Late Toxicities With Daily Versus Every-Other-Day 5-Fraction Partial Breast Radiation Therapy.

Purpose: Partial breast irradiation (PBI) delivered with intensity modulated radiation therapy over 5 fractions every other day represents an attractive, convenient method of delivering adjuvant radiation therapy for well-selected patients without compromising oncologic or toxicity outcomes. Condensing this regimen to a week of treatment through consecutive daily delivery may further increase patient convenience, though a comparison of toxicities between daily and every other day regimens is limited.

Methods And Materials: We retrospectively reviewed 507 patients from an institutional registry undergoing PBI for ductal carcinoma in situ (DCIS) or early-stage breast cancer (T1-2N0/x) from 2015 to 2022. All patients received 30 Gy in 5 fractions with intensity modulated radiation therapy. Acute (toxicity within 90 days of treatment) and chronic toxicity were recorded.

Results: Of the 507 patients, 351 were treated every other day, and 159 were treated daily. Median follow-up was longer in the every-other-day group (2.4 vs 1.9 years, P < .001). With regards to acute toxicity, there was slightly reduced grade 1 to 2 dermatitis with daily treatment (39% every other day vs 35% daily, P = .06), while rates of fatigue (18% every other day vs 20% daily, P = .09) were similar. Rates of chronic toxicities were comparable between the two approaches, with no differences in the rates of chronic hyperpigmentation (14% every other day vs 14% daily, P = .97), telangiectasias (1% every other day vs 1% daily, P = .92), mild fibrosis/induration (13% every other day vs 13% daily, P = .91), and lymphedema (0% every other day vs 1% daily, P = .31).

Conclusions: Overall, 5-fraction PBI delivered daily appears to be well tolerated with similar acute and chronic toxicity to every other day fractionation.