Dose-finding study of oxaliplatin associated to capecitabine-based preoperative chemoradiotherapy in locally advanced rectal cancer.

Introduction: Proper administration timing, dose-intensity, efficacy/toxicity ratio of oxaliplatin added to fluoropyrimidin should be improved to safely perform two-drugs intensive preoperative chemoradiotherapy in locally advanced rectal cancer (LARC). This dose-finding study investigated recommended oxaliplatin dose, safety of oxaliplatin/capecitabine regimen and preliminary activity.

Methods: Schedule: oxaliplatin dose-levels, 35-40 mg/m2 /week; capecitabine 825 mg/m2 / twice daily, radiotherapy on rectum/nodes, 50/45 Gy, 45 and 9 boost/45 Gy, in first 5 and subsequent patients, 5 days/week, respectively; for 5 weeks. Pathologic complete response (pCR) 10% was projected in order to positively affect clinical outcome.

Results: Seventeen fit <75 years patients enrolled: median age 60; young-elderly 4 (23%); T3/T4, 15/2, N0/N1/N2, 7/9/1. At first dose-level, no dose-limiting toxicity (DLT). At second, 2 DLT, G3 mucositis, G3 thrombocytopenia, in 2/6 patients (33%). Oxaliplatin recommended dose, 40 mg/m2 /week. Cumulative G3-4 toxicities: mucositis 6%, thrombocytopenia 6%. Limiting toxicity syndromes 18%, 25% in young-elderly, all single site. Objective response rate intent-to-treat 94%. Sphinter preservation 87%, pCR 6%. After 17 months follow-up, progression-free survival and overall survival were not reached.

Conclusions: Oxaliplatin can be safely added to preoperative capecitabine-based chemoradiotherapy at the recommended dose 40 mg/m2 /week, in LARC, with promising pCR and high activity.