Durable responses to tislelizumab plus fruquintinib and radiotherapy in refractory microsatellite stable metastatic colorectal cancer: a case report.

Immunotherapy has changed the landscape of contemporary cancer treatment. Different from microsatellite instability-high colorectal cancer (CRC), the microsatellite-stable (MSS) CRC shows little response to immunomonotherapy. Reasonable drug combinations may be a valuable exploration to solve this the dilemma. Here, we report a young patient with refractory metastatic rectal adenocarcinoma at stage IVb who achieved a durable partial response after receiving tislelizumab plus fruquintinib and well-timed local radiotherapy. To date, the patient has a progression-free survival of more than 12 months with obviously declined serum tumor markers, increased peripheral blood effector T cells, alleviated scrotal edema and improved quality of life. This case suggests that an immune checkpoint inhibitor combined with an anti-VEGFR-tyrosine kinase inhibitor and local radiation intervention might be an effective strategy for heavily pretreated metastatic CRC patients with MSS phenotype.