A clinical trial led by researchers at University College London and University College London Hospitals has produced what its chief investigator called “extremely encouraging” results in the treatment of bowel cancer, with every participant remaining cancer-free nearly three years after receiving a short course of immunotherapy before surgery. The findings, presented at the American Association for Cancer Research Annual Meeting 2026 in San Diego, suggest the approach could fundamentally change how a specific subset of bowel cancer is treated.
The NEOPRISM-CRC trial, which used the immunotherapy drug pembrolizumab in place of post-surgical chemotherapy, has produced outcomes that diverge sharply from current standard care, where roughly one in four patients with the same genetic cancer profile would typically see a recurrence within three years.
What the Trial Found
Patients in the trial received up to nine weeks of pembrolizumab before surgery, instead of the usual approach of surgery followed by three to six months of chemotherapy. They were then monitored over time.
Initial results showed that 59% of patients had no signs of disease after pembrolizumab treatment and their planned bowel cancer operation. The latest follow-up data presented at AACR 2026 in April showed that 33 months later, none of the treated patients have experienced a return of their cancer.
By comparison, with the traditional approach of surgery followed by chemotherapy, about 25% of patients with this genetic profile would see their cancer return within three years, according to the study background.
“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,” said Dr. Kai-Keen Shiu, chief investigator of the trial, a consultant medical oncologist at UCLH and associate professor at UCL.
A Personalized Path Forward
Beyond the survival data, researchers analyzed blood samples to better understand why the treatment works and how to identify patients most likely to benefit. The team designed personalized blood tests that can show early on whether the treatment had worked and whether any cancer remained in the bloodstream.
“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,” Dr. Shiu said. “These tools could help us tailor our approach, identifying patients who are doing well and may need less therapy before and after surgery versus patients at higher risk of disease progression or relapse who need additional treatment.”
The translational research, led by UCL Cancer Institute and biotechnology company Personalis, marks a significant step toward precision oncology in bowel cancer, where treatment intensity could be matched to each patient’s individual response.
Professor Marnix Jansen, a clinician scientist and consultant histopathologist leading the translational research from UCL Cancer Institute and UCLH, described the broader value of the findings: “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.”
How the Treatment Works
Pembrolizumab is a type of immunotherapy known as a checkpoint inhibitor. It works by blocking a protein that prevents the immune system from recognizing and attacking cancer cells. The drug is already approved for use in several other cancer types and is sold under the brand name Keytruda.
The NEOPRISM-CRC trial focused on patients with a specific genetic profile of bowel cancer known as mismatch repair deficient (MMRd) or microsatellite instability-high (MSI-H), a subset that historically responds particularly well to immunotherapy. Roughly 15% of bowel cancer patients fall into this category.
A Patient’s Story
Christopher, one of the trial participants, was diagnosed with stage 3 bowel cancer and traveled to London from outside the city to take part in the study. He received three doses of immunotherapy over nine weeks, followed by surgery in May 2023.
“The outcome of the surgery was essentially that the cancer had melted away, these were the doctor’s words,” Christopher told UCL News. “The immunotherapy had had an almost immediate effect. I saw the images when I had the first colonoscopy and could see it was really quite a substantial lump. So as I say, it wasn’t a minor thing, I was diagnosed with stage 3 cancer.”
More than three years later, he remains cancer-free and has returned to normal activities. “I feel very lucky that I’ve reached the stage where my main problem is age rather than cancer or any illness,” he said.
Why This Matters
Bowel cancer is the fourth most common cancer in the United Kingdom, with approximately 44,000 new cases diagnosed each year. While the disease has historically affected older adults, diagnoses among people under 50 have been rising in recent years.
Survival rates depend heavily on early detection, with five-year survival reaching roughly 90% at stage one, dropping to 65% at stage three, and falling to about 10% at stage four.
The trial was conducted across multiple UK hospitals, including UCLH, University Hospital Southampton, St. James’s University Hospital in Leeds, and The Christie NHS Foundation Trust in Manchester. The research team plans further studies to refine which patients are most likely to benefit and how the personalized blood tests can be integrated into routine clinical care.
For now, the results offer a rare combination in cancer research: meaningful improvements in long-term outcomes paired with a path toward less aggressive, more personalized treatment for the patients most likely to benefit.
Disclaimer: This article is for informational purposes only and does not constitute medical advice. The treatment described is part of an ongoing clinical trial and is most effective for a specific genetic subset of bowel cancer. Treatment outcomes vary based on individual factors. Readers concerned about bowel cancer or considering treatment options should consult a qualified healthcare provider for personalized medical guidance.
