A British clinical trial has upended the standard treatment playbook for colorectal cancer, showing that a pre-surgery immunotherapy course can keep patients disease-free far longer than traditional chemotherapy. In the NEOPRISM-CRC study, participants with stage two or three bowel cancer received nine weeks of pembrolizumab before undergoing surgery, and nearly three years later, none have experienced a recurrence.
The trial, led by researchers at UCL and UCLH, enrolled 32 patients with MMR-deficient or microsatellite instability-high colorectal cancer, a genetic subtype representing roughly 10-15% of all bowel cancer cases in the UK. When tumors were examined after surgery, 59% showed no detectable cancer. More striking: the complete response held steady through 33 months of follow-up, with no patient experiencing a relapse in that window.
That durability dwarfs the baseline. Standard surgery followed by chemotherapy typically leads to cancer recurrence in about 25% of patients within three years. The shift to immunotherapy before rather than chemotherapy after surgery appears to reset the odds fundamentally.
Dr. Kai-Keen Shiu, chief investigator at UCL Cancer Institute and consultant medical oncologist at UCLH, framed the finding plainly. "Seeing that no patients have experienced a cancer recurrence after almost three years of follow-up is extremely encouraging," he said. "What is particularly exciting is that we now may be able to predict who will respond to the treatment using personalized blood tests and immune profiling."
That prediction capability emerged from a parallel discovery: blood tests designed to detect circulating tumor DNA showed remarkable predictive power. Patients whose tumor DNA vanished from circulation after immunotherapy were far more likely to remain cancer-free long term. Immune profiling of tumor tissue before treatment began also signaled which patients would respond well.
The implications stretch beyond the trial cohort. Researchers are now equipped to identify which patients might benefit from less intensive therapy and which require additional intervention, moving bowel cancer treatment toward genuine personalization.
Christopher Burston, a 73-year-old participant from Dorset, lived the transformation firsthand. Diagnosed in February 2023 after routine screening detected blood in his stool, he enrolled in the trial and underwent three immunotherapy doses over nine weeks. Surgery in May 2023 revealed the impact: what had been a substantial stage three tumor had largely dissolved. "The cancer had melted away," his doctors told him. Nearly three years later, Burston remains cancer-free and has resumed his normal life.
Bowel cancer ranks as Britain's fourth most common malignancy, with roughly 44,000 new cases annually. Survival varies sharply by stage: about 90% of stage one patients survive at least five years, dropping to 65% at stage three and 10% at stage four. Certain tumor types prove stubbornly resistant to standard treatment and prone to relapse.
Professor Marnix Jansen from UCL Cancer Institute emphasized the biological insight underlying the clinical gains. "These results not only confirm the durability of responses we saw almost three years ago, but also provide crucial biological insights into why immunotherapy is so effective in this setting," he said.
The research was presented at the American Association for Cancer Research Annual Meeting 2026 in San Diego and involved multiple UK hospitals, with biotech company Personalis contributing to the molecular analysis. The collaboration underscores how a focused trial in a genetically defined patient subgroup can yield both immediate clinical wins and tools that reshape how oncologists think about personalized cancer care.
Author Jessica Williams: "This trial shows what happens when you flip the conventional playbook: give immunotherapy first, surgery second, no chemo, and watch disease recurrence almost vanish. That's not incremental progress, that's a reset."
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