New results from the NEOPRISM-CRC trial show that a short course of immunotherapy before surgery may provide lasting protection for people with a specific genetic form of bowel cancer. The study, led by University College London and UCLH, followed 32 patients with stage two or three MMR-deficient/MSI-high bowel cancer who received pembrolizumab for up to nine weeks before their planned surgery. After 33 months of follow-up, none of the patients had experienced a cancer recurrence, according to findings presented at the AACR Annual Meeting 2026.
Notably, this included patients who still had small traces of disease after treatment; their remaining cancer did not grow or spread. By comparison, roughly 25% of patients receiving the standard approach of surgery followed by chemotherapy are expected to relapse within three years. The results extend earlier findings that showed major tumor shrinkage in 59% of patients after pembrolizumab alone.
Researchers also developed personalized blood tests to detect tumor DNA in the bloodstream. Disappearance of this DNA was strongly associated with having no cancer remaining, and the team hopes these tests, along with immune profiling, can help tailor treatment intensity after surgery. The trial enrolled patients at five UK hospitals, with translational work carried out by UCL and Personalis.