Peritoneal recurrence of colorectal cancer with microsatellite instability: Is immunotherapy alone more effective than surgery?

A 67-year-old man was treated with systemic chemotherapy and cytoreductive surgery for microsatellite instable (MSI), deficient mismatch repair (dMMR) right colonic cancer with peritoneal metastases. Disease was controlled only when anti-PD1 and anti-CTLA4 immune checkpoint inhibitors were introduced. The patient is in complete remission after five years of follow-up. First-line immunotherapy could have a central role in the management of patients with peritoneal recurrence from MSI/dMMR colorectal cancer even though amenable to surgical treatment.