A groundbreaking clinical trial is rewriting the rulebook for colorectal cancer treatment — with results that have stunned even the researchers behind it.
Zero Relapses After Nearly Three Years
In the NEOPRISM-CRC study, led by researchers at University College London (UCL) and University College London Hospitals (UCLH), patients with stage two or three colorectal cancer received just nine weeks of pembrolizumab (an immunotherapy drug) before undergoing surgery.
The results are extraordinary: 59% of patients had no detectable cancer after completing immunotherapy and surgery. And after 33 months of follow-up, not a single patient has relapsed — including those who still had small traces of cancer after treatment.
Why This Matters
Under standard care — surgery followed by months of gruelling chemotherapy — approximately 25% of patients see their cancer return within three years. The NEOPRISM approach appears to offer dramatically better protection with far less treatment burden.
Bowel cancer is the fourth most common cancer in the UK, with around 44,000 new cases annually. While it primarily affects older adults, diagnoses among people under 50 have been rising steadily.
Personalised Blood Tests
The research team also developed personalised blood tests that can detect whether cancer DNA is still circulating in the bloodstream — potentially allowing doctors to determine early whether treatment has been successful.
Dr Kai-Keen Shiu, Chief Investigator of the trial, said: "Seeing that no patients have experienced a cancer recurrence after almost three years of follow-up is extremely encouraging and strengthens our confidence that pembrolizumab is a safe and highly effective treatment to improve outcomes in patients with high-risk bowel cancers."
Who Could Benefit?
The trial focused on patients with a specific genetic subtype called MMR deficient/MSI-high bowel cancer, which accounts for about 10-15% of cases — roughly 2,000 to 3,000 patients each year in the UK alone.
The findings were presented at the American Association for Cancer Research (AACR) Annual Meeting 2026 in San Diego, marking a major milestone in the shift toward immunotherapy-first cancer treatment.
Sources: University College London, ScienceDaily, AACR Annual Meeting 2026 (May 6, 2026)
