MSS (Microsatellite Stable)

In this prospective, multicentre, randomized phase III trial, 612 locally advanced rectal cancer (LARC, T3-4/N+M0) patients with at least one high-risk features (lower location (≤5cm), cT4, cN2, MRF+, EMVI+, TD+) will be included, and randomly assigned to TNT group and iTNT group (1:1). TNT group receives long-course chemoradiotherapy (50Gy/25Fx concurrent with oral capecitabine) followed by 6 cycles of CAPOX. iTNT group receives short-course radiotherapy (25Gy/5Fx) followed by 6 cycles of Serplulimab combined with CAPOX. After the efficacy evaluation, the patients who achieves clinical complete response (cCR) will be managed by a watch and wait (W\&W) protocol and non-cCR patients will be recommended surgery. The primary endpoint is 3-year event-free survival rate (3yEFS%). The secondary endpoints include the complete response (CR, pathological complete response \[pCR\] plus cCR) rate, 3-year organ preservation rate, 3-year disease-free survival rate (3yDFS%), 3-year local recurrence free survival rate (3yLRFS%), 3-year distant metastasis free survival rate (3yDMFS%), 3-year overall survival rate (3yOS%), grade 3-4 acute adverse effects (AE) rate, rate of surgical complications, anal functions and quality of life, etc.

Colorectal cancer (CRC) is the second leading cause of cancer-related death globally. BRAF V600E mutations occur in approximately 12% of metastatic CRC (mCRC) patients, conferring an extremely poor prognosis with a median overall survival (OS) of only 11 months for standard chemotherapy. Most BRAF V600E-mutant mCRC are microsatellite stable (MSS) and do not benefit from single-agent PD-1/PD-L1 inhibition. Preclinical and clinical evidence indicates that BRAF inhibition in combination with EGFR blockade can induce DNA damage, trigger a deficient mismatch repair (dMMR) phenotype, and increase tumor mutational burden (TMB), thereby sensitizing MSS tumors to immune checkpoint inhibition. This provides a strong rationale for combining BRAF/EGFR inhibitors with anti-PD-1 and anti-CTLA-4 immunotherapy. This is a single-arm, open-label, Phase II clinical trial. The primary objective is to evaluate the efficacy and safety of the triplet combination of sintilimab (anti-PD-1), ipilimumab N01 (anti-CTLA-4), cetuximab (anti-EGFR), and dabrafenib (BRAF inhibitor) in patients with MSS, BRAF V600E-mutant mCRC.