Nine Weeks of Immunotherapy Keeps Colon Cancer Patients Relapse-Free

A clinical trial has delivered some of the most hopeful news in years for certain colon cancer patients: a short course of immunotherapy before surgery that has left them relapse-free for nearly three years. Reported on May 6, 2026, the NEOPRISM-CRC trial gave 32 patients with stage 2 or 3 bowel cancer just nine weeks of the drug pembrolizumab ahead of their operation, challenging the standard path of surgery followed by months of chemotherapy.

The patients all had a particular genetic subtype known as MMR-deficient or MSI-high, which makes up roughly 10 to 15 percent of bowel cancer cases and tends to respond especially well to immunotherapy. The results were striking. In 59 percent of patients, no detectable cancer remained after the immunotherapy and surgery. And after a median follow-up of 33 months, the chief investigator reported that none of the patients had experienced a relapse, a sharp contrast with standard care, in which about a quarter of patients see their cancer return within three years.

“Reported on May 6, 2026, the NEOPRISM-CRC trial gave 32 patients with stage 2 or 3 bowel cancer just nine weeks of the drug pembrolizumab ahead of their operation, challenging the standard path of surgery followed by months of chemotherapy.”

The trial was led by University College London and University College London Hospitals, and the findings were presented at the American Association for Cancer Research Annual Meeting 2026. By harnessing the patient’s own immune system to attack the tumor before it is removed, the approach may spare many people the grueling side effects of prolonged chemotherapy while delivering better outcomes.

As always, this is one relatively small trial, and the patients will need to be followed for longer to confirm that the benefit endures, while larger studies test whether the results hold up broadly. Even so, the lead investigator called it “extremely encouraging,” and rightly so. For patients facing a colon cancer diagnosis, the prospect of a shorter, gentler, and more effective treatment is exactly the kind of progress that medicine is meant to deliver.