e16133 Background: Neoadjuvant chemoradiotherapy (NCRT) is the standard of care for stage II/III rectal cancer (RC) for its local-control effect. As advancement in surgery, local relapse was no longer the primary cause of failures, especially in low/intermediated-risk stage II/III RCs, in which benefit of radiotherapy in local control wasn’t shown in our previous trial. Distant relapse has become the major form of recurrences, and occurs at an increased rate when chemotherapy was delayed. This trial explores the effect of neoadjuvant chemotherapy (NCT), and the possibility of early assessment of chemotherapeutic response in low/intermediated-risk stage II/III RCs. Methods: This prospective, single arm, phase II trial planned to enroll 60 low/intermediate-risk stage II/III mid-low RCs (low: cT3a-bN0-1M0 MRF(-); mid: cT3a-c or T4aN0-1M0). 4 cycles of CAPOX NCT were scheduled. Rectal MRI, transanal US, endoscopy, CT were examined prior to treatment and after every two cycles. The primary outcome was the clinicopathological response, defined as pathological TRG0-1, TRG2 without tumor length increase, or TRG3 with tumor length regression over 30%. This study was approved by the Ethics Committees of West China Hospital and registered at ClinicalTrials.gov (NCT03666442). Results: From Dec. 2017 to Oct. 2019, 61 eligible patients were enrolled. Two patients received 3 cycles and 2 had only 2 cycles of chemotherapy due to intolerable adverse effects; 57 cases finished 4 cycles. In pathological evaluation, 13 patients (21.3%) were complete response (pTRG0) with one positive node in one patient; 5 cases were pTRG1; 26 were pTRG2; 17 had no response (pTRG3). 48 cases (78.7%) were responders. In the ROC curve predicting the responder via the 2-cycle regression in tumor length, the AUC was 0.864 (95%CI (0.764,0.963), p < 0.001), and the best cutoff regression rate after 2 cycles NCT was 27%. With this cutoff, the sensitivity was 83.3%; specificity was 84.6%; accuracy was 83.6%; positive likelihood ratio was 5.42; negative likelihood ratio was 0.20. Conclusions: NCT achieve more favorable pCR and tumor response rate in low/intermediated-risk stage II/III RCs, comparing to previous studies. The tumor regression after 2 cycles NCT had good accuracy in diagnosing the chemotherapeutic response. This early assessed chemosensitivity may become another feature for tailored use of neoadjuvant treatments, further cohort study will be conducted. Clinical trial information: NCT03666442 .
Multicenter Phase Ii Trial of Neoadjuvant Chemotherapy with Mfolfox6 for Stage Ii/Iii Rectal Cancer with a T3/T4 Tumor Fact Trial
