Long-term response to sintilimab, bevacizumab and chemotherapy in heavily pretreated microsatellite stable colon cancer.

Most advanced colorectal cancer patients with proficient DNA mismatch repair or microsatellite stability (MSS) are insensitive to immune checkpoint inhibitor therapy. This report describes a heavily pretreated refractory colon adenocarcinoma patient with MSS. After experiencing four lines of treatment, the patient received the fifth-line therapy with the combined sintilimab, bevacizumab and chemotherapy. She achieved a long-term clinical outcome. The patient's progression-free survival after the fifth-line therapy was approximately 9.3 months, and her overall survival was approximately 57 months. To the best of our knowledge, this case represents the first report of durable clinical benefit from combination of an immune checkpoint inhibitor, bevacizumab and chemotherapy in a heavily pretreated patient with refractory metastatic colon adenocarcinoma with MSS.