Nivolumab and Ipilimumab in Anti-PD1-Resistant dMMR/MSI mCRC

This study tests a combination of two immunotherapy drugs — nivolumab and ipilimumab — in patients with metastatic colorectal cancer whose cancer has a specific DNA repair defect (called dMMR or MSI-high) but stopped responding to anti-PD1 immunotherapy alone. **You may be eligible if...** - You are 18 or older with metastatic colorectal cancer confirmed by biopsy - Your tumor has a DNA mismatch repair defect (dMMR) or is microsatellite instability-high (MSI-H) - Your cancer progressed during or within 6 months of stopping a PD-1 immunotherapy drug - You have received prior standard chemotherapy treatments (including fluorouracil-based regimens and oxaliplatin) **You may NOT be eligible if...** - You are able to have all your metastases surgically removed - You have active autoimmune disease or are on high-dose steroids - You have serious heart, liver, kidney, or lung problems - You have untreated brain metastases Talk to your doctor to see if this trial is right for you.