Multicentre Randomised Phase III Trial of Capecitabine With or Without Irinotecan Guided by UGT1A1 Status in Patients Undergoing Neoadjuvant Chemoradiation for Locally Advanced Rectal Cancer

Abstract

Background: Our previous study identified irinotecan dose differentiated by UGT1A1 genotype in the neoadjuvant chemoradiotherapy and showed improved pCR. The objective of this phase III study was to further investigate irinotecan combined with capecitabine-based chemoradiotherapy as preoperative treatment for locally advanced rectal cancer. Methods: We underwent a randomized, open-label, multicenter, phase 3 trial in China. Eligible patients with clinical T3-4 and/or N+ rectal adenocarcinoma were randomly allocated to the control arm (CapRT arm): pelvic radiation of 50 Gy/25 fractions with concurrent capecitabine 825 mg/m2 twice daily 5 days per week, followed by a cycle of XELOX two weeks after the end of CRT; or the experimental arm (CapIriRT arm): radiation with capecitabine 625 mg/m2 twice daily 5 days per week and combined with weekly irinotecan of 80mg/m2 for UGT1A1*1*1 or 65mg/m2 for UGT1A1*1*28, followed by a cycle of XELIRI. The primary endpoint is pathological complete response (pCR). This trial was registered with ClinicalTrials.gov, number NCT02605265. Findings: Of the 360 patients initial enrolled, 356 were evaluated in mITT dataset (both 178 in two arms). Surgery was performed in 87% and 88% of patients in two arms, with 39% and 31% of patients got abdominoperineal resection respectively. The pCR rates were 18% (27/154) in CapRT arm and 34% (53/157) in CapIriRT arm (risk ratio 1.93; 95% CI 1.28–2.89, p=0.001), additional 4 and 6 patients were marked as complete clinical response (cCR). therefore, the overall CR rates were 17% and 33%, respectively. The most common grade 3-4 toxicities during CRT were leukopenia (3% vs. 25%), neutropenia (2% vs. 20%), and diarrhoea (2% vs. 13%). The overall rate of surgical complications were not significantly different between arms (11% vs. 15%). Interpretation: Adding irinotecan guided by UGT1A1 to capecitabine-based neoadjuvant chemoradiotherapy significantly increases complete tumor response. The treatment toxicities were increased but tolerable. Trial Registration: ClinicalTrials.gov, number NCT02605265 Funding Information: This study was funded by grants from Fudan University Shanghai Cancer Center (YJLC201601) and National Natural Science Foundation of China (81773357). We thank the patients, investigators, and institutions involved in this study. Competing Interest Declaration: I/We declare no competing interests. Ethical Approval Statement: The study was approved by the central ethics committee of Fudan University Shanghai Cancer Center (Shanghai, China)