By Morgan Nwanguma
A short course of immunotherapy given before surgery is showing remarkable success in a specific form of colorectal cancer. In a UK-led clinical trial, patients who received just nine weeks of pembrolizumab before surgery remained cancer-free nearly three years later, raising questions about the current standard treatment of surgery followed by several months of chemotherapy.
The findings come from the NEOPRISM-CRC study, which investigated whether immunotherapy administered before surgery could improve outcomes for patients with stage two or stage three colorectal cancer. Researchers from University College London and University College London Hospitals found that a brief pre-surgical course of pembrolizumab produced strong and durable responses.
After surgery and immunotherapy, 59% of patients had no detectable signs of cancer. More importantly, following 33 months of monitoring, none of the participants experienced a recurrence of the disease.
This included patients whose tumors disappeared completely as well as those who still had tiny amounts of cancer remaining after treatment. In every case, the residual cancer remained stable and did not spread or return over time.
The results differ sharply from current standard treatment outcomes, where roughly one in four patients who undergo surgery followed by chemotherapy are expected to experience a relapse within three years. The new findings suggest that starting treatment with immunotherapy could provide more durable protection against recurrence.
Researchers also examined why the therapy appeared to work so effectively and how doctors might identify the patients most likely to benefit. Using blood samples, the team developed personalized tests capable of detecting traces of tumor DNA circulating in the bloodstream.
These blood-based tests could eventually help physicians determine at an earlier stage whether treatment has successfully eliminated the cancer.
Dr. Kai-Keen Shiu, Chief Investigator of the trial from UCL Cancer Institute and a Consultant Medical Oncologist at UCLH, stated: “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.
“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. 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.”
Understanding Bowel Cancer Risk and Survival
Bowel cancer is the fourth most commonly diagnosed cancer in the UK, with around 44,000 new cases recorded annually. Although the disease is more common among older adults, cases in people under the age of 50 have been increasing in recent years.
Survival rates are strongly linked to how early the disease is identified. Approximately 90% of patients diagnosed with stage one bowel cancer survive for at least five years. That figure falls to about 65% for stage three disease and declines sharply to around 10% for stage four cancer. Certain tumor subtypes are also known to be more aggressive, making them more likely to resist treatment and recur.
Trial Details and Patient Group
The NEOPRISM-CRC study enrolled 32 patients with stage two or stage three colorectal cancer carrying a genetic subtype known as MMR-deficient/MSI-high bowel cancer. This subtype represents roughly 10% to 15% of cases, affecting an estimated 2,000 to 3,000 patients each year in the UK.
Instead of receiving the standard treatment of surgery followed by months of chemotherapy, participants were given up to nine weeks of pembrolizumab before surgery and were monitored afterward to assess long-term outcomes.
The latest results were presented at the American Association for Cancer Research Annual Meeting 2026. The research was led by University College London and University College London Hospitals, with support from several UK hospitals and contributions from biotech company Personalis.
Why Immunotherapy Appears So Effective
Researchers also uncovered new clues about why immunotherapy may produce such durable responses in these patients.
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Bottom of Form
Professor Marnix Jansen from UCL Cancer Institute and UCLH remarked: “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.”
Scientists discovered that when tumor DNA disappeared from the blood, patients were extremely likely to stay cancer-free for long.
Yanrong Jiang, first author of the study, noted: “As a research team, we were thrilled to be able to follow patients very closely using the personalized blood tests. When tumor DNA disappeared from the blood, patients were much more likely to have no cancer remaining, and this matched the long-term results we’re now seeing.
“In addition, we also saw that immune profiling from tumor tissue, before patients start their first cycle of treatment, can help to predict response. We hope these tests may be used to guide treatment decisions in a more practical and timely way.”
Patient Story projects Real-World Impact
Christopher Burston, a 73-year-old patient from Portland, Dorset, was diagnosed with colorectal cancer in February 2023 following regular tests spotted blood in his stool.
He said: “One came back with indications of blood in my stool. I went through further tests, and it was at the colonoscopy that they identified a cancer in my bowel.”
Shortly after being diagnosed, he was invited to take part in the NEOPRISM trial and decided to enroll, traveling to London to receive treatment.
Over a nine-week period, he underwent three rounds of immunotherapy before having surgery in May 2023. He recovered well after the procedure and experienced very few side effects.
He said: “The outcome of the surgery was essentially that the cancer had melted away, these were the doctor’s words. 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.”
Almost three years afterwards, he is still cancer-free and has since gone back to his usual activities.
Christopher said: “The recovery went fine. I didn’t have any problems. And since then, I’ve been feeling pretty much back to normal. I feel very lucky that I’ve reached the stage where my main problem is age rather than cancer or any illness.”
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