First-line treatment with a combination of immunotherapy, anti-EGFR monoclonal antibodies, and chemotherapeutics for unresectable left KRAS/BRAF wild-type microsatellite-stable colorectal cancer: a case report.

Immunotherapy shows limited efficacy in microsatellite-stable (MSS) colorectal cancer. This case report describes a 40-year-old male with left-sided kirsten rat sarcoma viral oncogene homolog (KRAS)/v-raf murine sarcoma viral oncogene homolog B (BRAF) wild-type, MSS colorectal cancer and liver metastases who achieved complete regression of metastases following first-line treatment with toripalimab, cetuximab, and FOLFIRI (irinotecan + fluorouracil + leucovorin), enabling curative-intent surgical resection. The patient achieved a progression-free survival of 16 months and an overall survival exceeding 20 months. The regimen demonstrated excellent tolerability without severe adverse events, suggesting that this triple combination represents a promising strategy for conversion therapy in advanced MSS colorectal cancer.