Evaluation of two different schedules of bevacizumab (BEV) with oxaliplatin (OXA), raltitrexed (TOM), levo-folinic acid (LFA), and 5-fluorouracil (5-FU) during preoperative (preop) pelvic RT in high-risk locally advanced rectal cancer (HR-LARC) patients (pts)

e14546 Background: OXA, RTX, 5FU, and LFA during preop pelvic RT produced a high rate of complete (TRG1) or subtotal (TRG2) tumor regression in HR-LARC. BEV might enhance response to chemoradiotherapy (CH-RT), but scheduling of BEV could be critical. Therefore, we added BEV to CH-RT in two different schedules to evaluate their feasibility and activity. According to the Simon's two-stage design, assuming a hypothesis of a 50% TRG1 (α=0.05, β=0.20), at least 6/16 TRG1 should be obtained to continue pts accrual in every schedule. Methods: Inclusion criteria were: cT4, cN+, cT3(<5 cm from the anal verge and/or +ve CRM), resectable M1. Pts received 3 biweekly courses(c) of OXA (100 mg/m2)/TOM (2.5 mg/m2) on day 1, and 5FU (800 mg/m2)/LFA(250 mg/m2) on day 2 during pelvic RT (45 Gy). BEV (5 mg/kg) was given biweekly from day -14 for 4 c in schedule A, and from day -4 for 2 c in schedule B. Toxicity was graded with NCI-CTCv3. Changes of circulating endothelial cells (CECs)assessed by flow cytometry in 17 (7 A; 1...