MMR deficiency, present in 15.3% of tested cases (Table 4), interacted significantly with high comorbidity burden (CCI ≥ 5), resulting in a 42.9% event rate (OR 8.57, 95% CI 1.67–44.0, p = 0.009; Table 8), nearly double the 28.0% risk observed in MMR-proficient patients with CCI ≥ 5. The gene discussed is MRC1; the disease is mismatch repair cancer syndrome 1.