Concomitant Boost Versus Sequential Boost in Breast Conservative Therapy for Early Stage Breast Cancer

Abstract

Purpose/Objective: To compare concomitant boost irradiation (CBI) to sequential boost irradiation(SBI) to the tumor bed by 3DCRT after breastconserving surgery (BCS) regarding target coverage, dose homogeneity, dose to organs at risk, acute toxicity, late toxicity, local control, DFS and cosmesis. Materials and Methods: Sixty patients were randomized after BCS to receive concomitant boost irradiation for 5 weeks (for each fraction, the breast and boost planning target volumes 'PTVs' received 2 Gy and 2.4 Gy, to a total dose of 50 Gy and 60 Gy respectively) or a biologically equivalent sequential boost (the breast received 2 Gy x 25 fractions followed by 2 Gy x 8 fractions boost to the tumor bed). Threedimensional conformal beams with wedges were used. Acute toxicity was evaluated using RTOG criteria and cosmesis was evaluated using Gray score. Results: Target coverage was adequate with both techniques (V45 for breast CTV = 98.5% vs 98.7%for CBI and SBI respectively, p=0.6; and D95 for boost PTV -after calculation of biologically equivalent dose 'BED'= 62.9 Gy vs 63.3 Gy respectively). There was no statistically significant difference between the two groups regarding the doses to OAR (i.e. mean heart dose, heart V40, lung V20, mean dose to contra lateral breast and mean dose to the thyroid gland). The 2 groups were comparable regarding cardiac, pulmonary, neurologic and skin toxicity with 20 (33.4%) of our patients developing GII or worse skin toxicity, but with no impact on cosmetic outcome (median=7 in each arm, p=0.8). After a median follow-up of 25 months, disease free survival was 83.3% in the sequential arm versus 93.3% in the concomitant arm (P-value= 0.170). Only one patient in the study developed local recurrence; that patient was in the sequential boost arm, with loco-regional recurrence free survival (LRRFS) of 95.1% for our whole patient cohort. Conclusions: Concomitant boost irradiation by 3DCRT is non-inferior to sequential boost irradiation after BCS regarding acute toxicity, cosmetic outcome, local control and DFS. It can be used to reduce the number of treatment fractions without increasing toxicity or hindering patient outcome.