Outcome of 15 Versus 5 Fractions in Adjuvant Breast Radiotherapy in Women Over 65 Years

Over the age of 65, uptake of adjuvant radiotherapy after surgery for breast cancer declines, even in women with poor prognostic stage or adverse tumor characteristics. Lowering the number of fractions may reduce reluctancy for radiotherapy in this age group. In a preceding prospective phase I-II trial, evaluating EBRT over 10 days, results on technical feasibility and acute toxicity were positively evaluated. However, data on the chronic effects of breast irradiation using high doses per fraction are still sparse. This trial is developed to compare standard hypo-fractionation in 15 fractions (if needed with simultaneously integrated boost - SIB) with highly accelerated radiotherapy in 5 fractions. Patients referred for adjuvant radiotherapy after breast conserving surgery will preferably be randomized, depending on the indication, to a study-arm with whole breast irradiation (WBI) +/- SIB or to a study-arm with WBI+/- SIB and lymph node irradiation (LNI). If patients after breast conserving surgery (BCS) have a strong preference for 5 or 15 fractions, they will be invited to enter the parallel observational arm (patient preference). Patients referred for adjuvant radiotherapy after mastectomy +/- LNI accepting to participate, can choose a 5 or 15-fraction schedule. No randomization is foreseen in this last observational group.