[Concurrent administration of adjuvant chemotherapy and radiotherapy after breast-conservative surgery enhances late toxicities]

International audiencePURPOSE: In 1996, a multicenter randomized study comparing after breast-conservative surgery, sequential vs concurrent adjuvant chemotherapy (CT) with radiation therapy (RT) was initiated (ARCOSEIN study). Seven hundred sixteen patients were included in this trial. After a median follow-up of 6.7 (4.3-9) years, we decided to prospectively evaluate the late effects of these two strategies. PATIENTS AND METHODS: A total of 297 patients were asked to follow-up from the five larger including institutions. Seventy-two percent (214 patients) were eligible for late toxicity. After breast-conserving surgery with axillary dissection, patients were treated either with sequential treatment with CT first followed by RT (arm A) or CT administered concurrently with RT (arm B). In all patients, CT regimen combined mitoxantrone (12 mg/m(2)), 5-FU (500 mg/m(2)), and cyclophosphamide (500 mg/m(2)), 6 cycles (day 1-day 21). In arm B, patients received concurrently the first 3 cycles of CT with RT. In arm A, RT started 3 to 5 weeks after the 6th cycle of CT. Conventional RT was delivered to the whole breast using a 2 Gy-fraction protocol to a total dose of 50 Gy (+/-boost to the primary tumour bed). The assessment of toxicity was blinded to treatment and was graded by the radiation oncologist according to the LENT-SOMA scale. Skin pigmentation was also evaluated using a personal 5-points scoring system (excellent, good, moderate, poor, very poor). RESULTS: Among the 214 evaluated patients, 107 were treated in each arm. The two populations were homogeneous for patients', tumors' and treatment characteristics. Subcutaneous fibrosis (SF), telengectasia (T), skin pigmentation (SP), and breast atrophy (BA) were significantly increased in arm B. Twenty patients experienced grade superior or equal to 2 (SF) in arm B vs five in arm A (P=0.003). Twenty-five and seven patients showed grade superior or equal to 2 (T) in arm B and A, respectively (P=0.001). Forty-four and twenty patients showed grade superior or equal to 2 (BA) in arm B and A, respectively (P=0.0006). Thirty patients experienced grade superior or equal to 3 (SP) in arm B vs fifteen in arm A (P=0.02). No statistical difference was observed between the two arms concerning grade superior or equal to 2 pain, breast oedema, and lymphoedema. No deaths were caused by late toxicity. CONCLUSION: Following breast conserving surgery, the concurrent use of CT with RT is significantly associated with an increase incidence of grade 2 or greater late side effects