A randomized phase II trial of consolidation chemotherapy after preoperative chemoradiation (preop CRT) versus CRT alone for locally advanced rectal cancer (LARC).
3606 Background: In LARC, preop CRT followed by total mesorectal excision (TME) is a standard of care. Recently consolidation chemotherapy after CRT was shown to be safe and to improve pathologic complete response (pCR) rate in LARC. We aimed to evaluate downstaging (DS) rate (the proportion of ypT0-2N0M0) of CRT followed by consolidation chemotherapy (capecitabine and oxaliplatin: CapOx) compared to that of CRT alone. Methods: Patients (pts) with adenocarcinoma of rectum(≤ 12cm from anal verge), ECOG PS 0 or 1, and cT3-4NxM0 were enrolled. CRT (50-50.4Gy/25-28fx) with Cap (825mg/m2/day for 5 days per week throughout CRT) followed by TME was planned in Arm A (control arm). In Arm B, 2 cycles of CapOx was given a week after completion of CRT before TME (Cap 850mg/m2/day from day 1 to day 14; Ox 100mg/m2on day 1; q 3w). 110 pts (55 per arm) were needed to show improvement of DS rate in per-protocol population (PP set) from 30% to 50% in arm B with one-sided α = 0.15, 1- β = 0.85, and follow-up loss in 5%. Results: From 9/2014 Sep to 2/2016, 110 (56 in arm A; 54 in arm B) were enrolled; 108 (55 in arm A; 53 in arm B) were randomized and started study treatment. Median age was 56 years; male/ECOG PS 1/cT4 was 76%/70%/18%. 100 pts (54 in arm A; 46 in arm B) completed CRT ± CapOx and surgery (R0 or R1 resection), while 8 (1 in arm A, 7 in arm B) dropped out mainly due to consent withdrawal. 2 of each arm underwent non-TME; that leaves 96 (52 in arm A and 44 in arm B) in PP set. Relative dose intensity of CapOx was 96% (Cap) and 95% (Ox). The main treatment outcome is described in table. The mean interval days between completion of CRT and surgery was significantly longer in arm B (52.9 vs 61.3, p < 0.0001). Conclusions: 2 cycles of CapOx after completion of CRT was feasible and safe, and it showed improvement in DS rate, even with high dropout rates (13%). Clinical trial information: NCT01952951. [Table: see text]