Updated survival outcome of regorafenib, ipilimumab, and nivolumab in refractory microsatellite stable non-liver metastatic colorectal cancer: A phase I nonrandomized clinical trial

Background: Combination regorafenib, ipilimumab, and nivolumab (RIN) was evaluated in a phase 1 nonrandomized study (NCT04362839) of refractory microsatellite stable (MSS) metastatic colorectal cancer. Promising antitumor activity was previously reported in the non-liver metastatic (NLM) population. This updated analysis describes long-term survival outcomes in the NLM cohort and highlights durable remissions with potential cure following completion of RIN therapy. Methods: Between May 2020 and January 2022, 39 patients with refractory MSS metastatic colorectal cancer were enrolled. Patients received RIN until progression, unacceptable toxicity, or completion at two years. The primary endpoint was recommended phase 2 dose (RP2D) selection. Secondary endpoints were safety, overall response rate (ORR), progression-free survival (PFS) and overall survival (OS) at the RP2D level. Results: 22 patients with refractory non-liver metastatic MSS colorectal cancer were treated at the RP2D of RIN. ORR was 36.4 % (8/22 patients), and median PFS was 5.0 months (95 % CI: 3-9). After a median follow-up of 42 months, the 1-, 2-, and 3-year PFS rates were 24.1 %, 24.1 %, and 19.3 % by RECIST. The median OS was 27.5 months (95 % CI: 14.0 to NE). At data cutoff, 6 patients had ongoing clinical benefit, including 3 responders who remain disease-free > 18 months after treatment completion. Conclusion: With extended follow-up, RIN combination therapy demonstrated durable clinical benefit in a subset of patients with NLM MSS metastatic colorectal cancer, including potential cure in 3 responders who remain disease-free > 18 months after treatment completion.