Patients with resectable mismatch repair-deficient (dMMR) rectal cancer receiving extended neoadjuvant therapy with the anti-PD-1 antibody dostarlimab have previously been shown to have a 100% clinical complete response (cCR) rate. Now, an update from this trial confirms this excellent response rate and provides data on the durability of many of these responses, as well as on the efficacy of this approach in patients with other resectable dMMR solid tumours.

A total of 49 patients with dMMR rectal cancer were enrolled in cohort 1. In cohort 2, 67 patients with non-rectal resectable dMMR solid tumours were enrolled, including 33 with colon cancer and 15 with gastric cancer. Patients with a cCR could elect to receive nonoperative management after completion of treatment (9 cycles of dostarlimab). In cohort 1, overall response and sustained cCR at 12 months were the primary end points. The analyses performed in cohort 2 are exploratory.