Pre-surgery immunotherapy kept a group of bowel cancer patients cancer-free for nearly three years, while personalized blood tests helped predict treatment response.
Patients with a specific form of bowel cancer who received a short course of immunotherapy before surgery, rather than chemotherapy afterward, have remained cancer-free for nearly three years, according to updated findings from the NEOPRISM-CRC clinical trial led by researchers at UCL and UCLH.
The new results, scheduled to be presented at the American Association for Cancer Research (AACR) Annual Meeting 2026 in April, build on earlier data showing that nine weeks of preoperative treatment with pembrolizumab significantly reduced tumors in patients with stage 2 or stage 3 bowel cancer.
Early findings showed that 59% of patients had no detectable cancer after completing pembrolizumab treatment and undergoing surgery.
After 33 months of follow-up, none of the patients in the study have seen their cancer return. This includes patients whose cancer had completely disappeared as well as those who still had small remaining traces that did not grow or spread over time.
Personalized Blood Tests May Predict Treatment Response
About 25% of patients who receive standard treatment with surgery followed by chemotherapy are expected to relapse within three years. The new findings suggest that a brief course of immunotherapy before surgery may provide longer-lasting cancer control for this subtype of bowel cancer compared with conventional treatment.
Researchers also studied blood samples to understand why the therapy works so well and to identify which patients are most likely to benefit. They developed personalized blood tests designed to detect whether treatment was successful and whether any cancer remained in the bloodstream.
Dr. Kai-Keen Shiu, chief investigator of the trial from the UCL Cancer Institute and a consultant medical oncologist at UCLH, 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.
“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.”
Rising Bowel Cancer Rates Highlight Need for Better Treatments
Bowel cancer is the fourth most common cancer in the UK, with around 44,000 new cases diagnosed each year. Although it mainly affects older adults, cases among people under 50 have increased in recent decades.
As with many cancers, early detection greatly improves outcomes. About 90% of patients treated for stage 1 bowel cancer survive at least five years. However, some tumor subtypes respond poorly to treatment and are more likely to return. Five-year survival rates drop to 65% for stage 3 disease and 10% for stage 4 disease.
The NEOPRISM-CRC trial enrolled 32 patients with stage 2 or stage 3 bowel cancer carrying a specific genetic profile known as MMR deficient/MSI-high bowel cancer from five hospitals across the UK. Roughly 10% to 15% of patients with stage 2 or stage 3 bowel cancer have this genetic subtype, representing an estimated 2,000 to 3,000 cases annually in the UK.
Patients received up to nine weeks of pembrolizumab before surgery instead of the standard approach of surgery followed by three to six months of chemotherapy. Researchers then monitored the patients over time.
Researchers Explore Why Immunotherapy Works So Well
The latest phase of the ongoing trial, presented this month at AACR in San Diego, California, was led by UCL and UCLH. University Hospital Southampton, St. James’s University Hospital in Leeds, and the Christie NHS Foundation Trust in Manchester also contributed by recruiting patients and supplying translational research samples. All translational research was carried out by UCL and biotechnology company Personalis.
Professor Marnix Jansen, a clinician scientist and consultant histopathologist leading the trial’s translational research at the UCL Cancer Institute and UCLH, said, “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.”
Yanrong Jiang, first author of the latest abstract and a clinical PhD student at the UCL Cancer Institute, said, “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 Says Immunotherapy Made Cancer “Melt Away”
Christopher Burston, a patient at UCLH, was diagnosed with bowel cancer in February 2023 after participating in routine screening. He had completed home bowel screening tests for several years before one returned positive.
Christopher, 73, from Portland, Dorset, 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.”
A few weeks after his diagnosis, his oncologist suggested he might qualify for the NEOPRISM clinical trial studying immunotherapy before surgery. Despite needing to travel to London for treatment, he chose to participate and was referred to UCLH.
He received three doses of immunotherapy over nine weeks before undergoing surgery in May 2023. He reported only mild side effects and recovered well after spending a week in the hospital.
Three Years Later, Patient Remains Cancer-Free
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.”
More than three years later, Burston remains cancer-free and has returned to his normal routine while continuing regular follow-up appointments.
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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