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

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.

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.

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).

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