Treatment with a single immune checkpoint inhibitor successfully treated advanced rectal cancer

Reference

Cercek A, Lumish M, Sinopoli J, et al. PD-1 blockade in mismatch repair–deficient, locally advanced rectal cancer. N Engl J Med 2022;386(25):2363-2376.

Synopsis

We don't usually cover case series studies in oncology, but this was a remarkable study that signals a potential sea change in the management of some cancers. Treatment of locally advanced rectal cancer generally involves chemotherapy and radiation to debulk the tumor, then surgery. These researchers identified patients with stage II or III rectal cancer who had a mutation resulting in a failure to repair DNA mismatches following replication (~ 5% to 10% of rectal cancers exhibit this mismatch repair defect). Rather than traditional chemotherapy and radiation, the researchers began treatment with a monoclonal antibody (dostarlimab) that is a PD-1 inhibitor. The patients received intravenous infusions every 3 weeks for 6 months. At the end of that period, they were supposed to undergo radiation therapy and chemotherapy. However, at the end of therapy with dostarlimab, the researchers found that all 12 who had completed therapy to date had no evidence of cancer. There has been no sign of recurrence during 6 to 25 months of follow-up, and no patient has required further therapy. Adverse events were generally mild.