Dostarlimab as Primary Treatment in MSI-High Solid-Tumor Cancers

Immune checkpoint inhibitors are highly effective treatment for DNA mismatch repair deficient (dMMR)/microsatellite instability (MSI)–high cancers. In a phase 2 trial of the PD-1 inhibitor dostarlimab, investigators reported a 100% rate of clinical complete response in 12 patients with MSI-high locally advanced rectal cancer, eliminating the need for chemotherapy, radiation, and surgery (NEJM JW Oncol Hematol Jun 29 2022 and N Engl J Med 2022; 386:2363). Now, they report findings in 49 patients with MSI-high rectal cancer and 54 patients with nonrectal MSI-high locally advanced solid tumors who completed 6-month treatment with dostarlimab.

In the rectal cancer cohort:

• All patients achieved a clinical complete response, and none received upfro…