Concurrent administration of adjuvant chemotherapy and radiotherapy after breast-conserving surgery enhances late toxicities: long-term results of the ARCOSEIN multicenter randomized study

International audience; PURPOSE: In 1996, a multicenter randomized study was initiated that compared sequential vs. concurrent adjuvant chemotherapy (CT) with radiation therapy (RT) after breast-conserving surgery (ARCOSEIN study). After a median follow-up of 6.7 years (range, 4.3-9 years), we decided to prospectively evaluate the late effects of these 2 strategies. METHODS AND MATERIALS: A total of 297 patients from the 5 larger participating institutions were asked to report for a follow-up examination. Seventy-two percent (214 patients) were eligible for evaluation of late toxicity. After breast-conserving surgery, 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 consisted of mitoxantrone (12 mg/m2), 5-FU (500 mg/m2), and cyclophosphamide (500 mg/m2), 6 cycles (Day 1 to Day 21). Conventional RT was delivered to the whole breast by administration of a 2 Gy per fraction protocol to a total dose of 50 Gy (+/- boost to the primary tumor 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 according to a personal 5-points scoring system (excellent, good, moderate, poor, very poor). RESULTS: Among the 214 evaluable patients, 107 were treated in each arm. The 2 populations were homogeneous for patient, tumor, and treatment characteristics. Subcutaneous fibrosis (SF), telangectasia (T), skin pigmentation (SP), and breast atrophy (BA) were significantly increased in Arm B. No statistical difference was observed between the 2 arms of the study concerning Grade 2 or higher pain, breast edema, or lymphedema. No deaths were caused by late toxicity. CONCLUSION: After 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.