The topline. San Juan, October 24, 2026. For a defined group of rectal cancer patients, the standard path of chemotherapy, radiation, and surgery may no longer be the only path. The FDA has granted accelerated approval to dostarlimab, an immunotherapy that blocks the PD-1 checkpoint so the immune system can recognize and attack cancer cells, for adults with stage II or III locally advanced rectal cancer whose tumors are MSI-H or dMMR. In the supporting trial, nearly half of independently reviewed patients held a complete clinical response for at least a year and were monitored without immediate surgery.

Key facts

The approval rests mainly on AZUR-1, a multicenter, single arm, open label trial in 154 previously untreated patients, who received dostarlimab 500 mg intravenously every three weeks for up to nine cycles. Response was judged by endoscopy, rectal MRI, and CT scans of the chest, abdomen, and pelvis. Patients who reached a clinical complete response entered a nonoperative management period, with close monitoring every four months for the first two years and every six months thereafter. Patients who did not reach a complete response, or whose disease returned, were evaluated for standard care at the treating team’s discretion.

The headline numbers need their denominators. By independent central review, 47 percent of 116 evaluable patients held a clinical complete response for at least 12 months, with a 95 percent confidence interval of 37 to 56 percent. By investigator assessment, 68 percent of 144 evaluable patients reached the same milestone. A clinical complete response is not the same as proven pathological clearance of the tumor, which is why the monitoring schedule, not just the drug, is part of the treatment.

Clinical relevance

This approval changes the conversation at diagnosis for one biomarker defined group, and the biomarker test is the gate: MSI-H or dMMR status must be established with an FDA authorized test before this path opens. For patients who do respond completely, avoiding surgery means avoiding its lasting effects on bowel, urinary, and sexual function, and on fertility. The accelerated status is the discipline in the story. It means the FDA judged the response data reasonably likely to predict benefit, with confirmatory follow-up still required. Present the option exactly that way: a real chance to avoid surgery under close surveillance, not a promise that surgery is gone for good. Common side effects included fatigue, rash, diarrhea, and itching, and like other checkpoint inhibitors, dostarlimab can trigger serious immune related reactions.

47%

That is the share of independently reviewed AZUR-1 patients who held a clinical complete response for at least 12 months. The investigator assessed figure was higher, at 68 percent, and the gap between the two readings is itself informative: independent review is the stricter lens, and it still cleared nearly half. The number that matters most in the exam room is the one behind the percentage. Every complete responder in this trial stayed on a surveillance schedule, because a complete clinical response is a finding to be watched, not a verdict to be filed away.

What we’re reading

  • U.S. Food and Drug Administration: the accelerated approval announcement for dostarlimab in locally advanced rectal cancer.
  • OncLive: Andrea Cercek on what the approval means for organ sparing treatment in dMMR disease.
  • The New England Journal of Medicine: the earlier dostarlimab rectal cancer studies from Memorial Sloan Kettering that built the case for this approval.