Study protocol of short-course radiotherapy combined with CAPOX and PD-1 inhibitor for locally advanced colon cancer: a randomized, prospective, multicentre, phase Ⅱ trial (TORCH-C)

Abstract Background The preliminary result of the TORCH trial has showed promising complete response (CR) for managing locally advanced rectal cancer (LARC) with neoadjuvant short-couse radiotherapy (SCRT) combined with chemotherapy and PD-1 inhibitor. For locally advanced colon cancer (LACC) with bulky nodal disease and/or clinically T4, neoadjuvant chemotherapy followed by colectomy with en bloc removal of regional lymph nodes is the suggested treatment. However, the CR rate is less than 5%. TORCH-C will aim to investigate neoadjuvant short-couse radiotherapy combined with chemotherapy and PD-1 inhibitor in LACC. Methods TORCH-C is a randomized, prospective, multicentre, double-arm, open, phase Ⅱ trial of SCRT combined with chemotherapy and immunotherapy in LACC with microsatellite-stable (MSS) patients and cT4 or bulky nodes. Eligible patients will be identified by the multidisplinary team. 120 patients will be randomized 1:1 to the intervention or control arm. The patients in the control arm will receive 4 cycles of capecitabine plus oxaliplatin (CAPOX). The patients in the intervention arm will receive SCRT, followed by 4 cycles of CAPOX and PD-1 inhibitor (Serplulimab). Both arms will receive curative surgery, followed by 4 cycles of CAPOX. The primary endpoint is pathologic complete regression (pCR). Discussion TORCH-C trial aims to investigate whether the combination of immunotherapy and chemoradiotherapy improves the treatment effect in LACC with MSS. TORCH-C will establish the TORCH platform, a key part of our long-term strategy to develop neoadjuvant treatment for colorectal cancer (CRC). Trial registration: The trial has been registered in ClinicalTrials.gov on Feburary 16, 2023 (Registration No. NCT05732493).