Revisiting the Role of Immunotherapy for Colorectal Cancer Treatment in Patients with Constitutional Mismatch Repair Deficiency

Patients with constitutional mismatch repair deficiency syndrome (CMMRD) usually develop multiple tumors at a young age. Chemotherapy was previously shown to be less effective in these tumors. Recent reports suggest immunotherapeutic treatment in CMMRD-associated tumors. Here, we present a CMMRD patient, successfully treated with immunotherapy for metastasized colorectal cancer (CRC). A young adolescent male was diagnosed with T2N2M1 cecum carcinoma with liver metastases. He received four initial doses of nivolumab (3 mg/kg) with ipilimumab (1 ml/ kg) every three weeks, followed by 41 doses of nivolumab alone every two weeks. A complete response was achieved; also pathological assessment of removed liver metastases was indicative of a complete response. At the time of writing, 14 months after end of treatment, the CRC had not recurred. Immunotherapeutic treatment resulted in a complete response of the primary CRC and metastases. Immunotherapy as first line treatment should be strongly considered in treatment of CMMRD-associated CRCs.