A pathological complete response after nivolumab plus ipilimumab therapy for DNA mismatch repair-deficient/microsatellite instability-high metastatic colon cancer: A case report

The standard treatment for colorectal cancer has always been surgery and chemotherapy, which may be used in combination to treat patients. Immune checkpoint inhibitors have been a significant advancement in the standard treatment of metastatic, unresectable colorectal cancer with deficient mismatch repair. However, little information is available about their use in neoadjuvant and conversion settings with only a few case reports and only one phase 2 trial. The present study reports the case of a large, locally advanced right-sided metastatic deficient mismatch repair/microsatellite instability-high colon cancer, which showed a pathological complete response after combination treatment with nivolumab and ipilimumab. To the best of our knowledge, resected metastatic colon cancer with a pathological complete response after treatment using dual immune checkpoint inhibitors has not been previously reported. Overall, this case report suggests the use of immune checkpoint inhibitors before colorectal surgery.