UCL NEOPRISM-CRC Trial Reports Zero Relapses for Bowel Cancer Patients Using Pre-Op Immunotherapy

UCL’s NEOPRISM-CRC trial shows 100% of bowel cancer patients remained cancer-free for 33 months using pre-op pembrolizumab instead of chemotherapy.

By: AXL Media

Published: Apr 21, 2026, 5:48 AM EDT

Source: Information for this report was sourced from University College London

Paradigm Shift in Colorectal Care Eliminates Post-Op Relapse

A transformative clinical study has achieved a perfect survival rate among patients with high-risk stage two and three bowel cancer by shifting the timing of immunotherapy. Results from the NEOPRISM-CRC trial, led by University College London (UCL), demonstrate that administering the drug pembrolizumab before surgery, rather than the standard post-operative chemotherapy, resulted in zero recurrences over nearly three years of monitoring. This breakthrough suggests that prime-loading the immune system while the tumor is still present allows for a more robust and durable anti-cancer response than the current reactive treatment model.

Nine-Week Regimen Melts Tumors in Majority of Participants

The clinical protocol involved a concise nine-week course of immunotherapy prior to scheduled surgical intervention. Initial findings from the study revealed that 59% of the 32 participants showed no evidence of live cancer cells at the time of their operation, a phenomenon described by clinicians as the tumor having "melted away." Even in cases where residual microscopic disease was present during surgery, the latest 33-month follow-up confirms that these remnants neither grew nor spread, indicating that the immunotherapy successfully sensitized the body's defenses to provide long-term surveillance.

Genetic Profiling Targets High-Risk MMR-Deficient Subtypes

The success of the trial was contingent on precise patient selection, focusing exclusively on individuals with mismatch repair deficient (MMR-deficient) or MSI-high bowel cancer. This specific genetic profile, which accounts for approximately 10-15% of stage two and three cases, is notoriously resistant to traditional chemotherapy but highly responsive to checkpoint inhibitors like pembrolizumab. By identifying these 2,000 to 3,000 annual UK cases early through genetic screening, oncology teams can now offer a highly targeted alternative that avoids the debilitating side effects of cytotoxic drugs.