First-line Nivolumab plus FOLFOXIRI/Bevacizumab in advanced RAS/BRAF-mutated colorectal cancer: efficacy, safety and biomarker discovery from the phase II NIVACOR trial.

Immunotherapy achieved remarkable results in patients with deficient mismatch repair (dMMR)/microsatellite instable (MSI) metastatic colorectal carcinoma (mCRC). However, its efficacy in proficient MMR (pMMR)/microsatellite stable (MSS) mCRC remains limited. In the phase II NIVACOR trial, we evaluated the activity and safety of FOLFOXIRI/bevacizumab plus nivolumab as first-line therapy in patients with RAS/BRAF-mutated mCRC (NCT04072198). The primary endpoint of the trial was the Objective Response Rate (ORR) whereas secondary endpoints were safety profile, overall survival (OS), progression free survival (PFS), duration of response (DoR) and quality of life. The primary endpoint was met. Among the 73 enrolled patients, 76.7% achieved an objective response (95% CI, 65.4 to 85.8%), while the disease control rate was 97.3% (95% CI, 90.5 to 99.7%). The median progression-free survival (mPFS) was 10.1 months (95% CI, 9.0 to 14.3 months), and the median overall survival (mOS) was not reached. Treatment-related adverse events of grade 3 or higher occurred in 48 patients out 73 enrolled patients (65.8%). Comprehensive genomic profiling and RNA sequencing analysis revealed genomic and transcriptomic profiles associated with treatment response in pMMR/MSS patients. Alterations in pathways such as PI3K/AKT, chemokine signaling and DNA repair showed correlation with treatment activity. These findings highlight the potential synergy between immune checkpoint inhibitors and cytotoxic chemotherapy in selected patients with pMMR/MSS mCRC.