Patients with a specific type of bowel cancer who were treated with a short course of immunotherapy before surgery instead of post-op chemotherapy have remained cancer-free after almost three years of follow-up, according to new results from the NEOPRISM-CRC clinical trial led by a team from UCL and UCLH.
The latest findings, to be presented at the American Association for Cancer Research (AACR) Annual Meeting 2026 in April, build on earlier results showing that nine weeks of pre-operative immunotherapy using the drug pembrolizumab led to major tumour shrinkage in patients with stage two or three bowel cancer.
Initial results indicated that 59% of patients had no signs of disease after treatment with pembrolizumab and their planned bowel cancer operation.
Now 33 months later, none of the treated patients have experienced a return of their cancer. This includes those who had no signs of cancer after treatment and those who still had small amounts remaining, which did not grow or spread during follow-up.
It's expected that around 25% of patients who have the standard surgery and post-op chemotherapy to relapse after three years, but this study suggests that a short course of immunotherapy before surgery can provide more durable, long-lasting cancer control for this type of bowel cancer, compared to surgery and chemotherapy.
Alongside the survival data, researchers analysed blood samples to better understand why the treatment is so effective and how to identify those most likely to benefit. They designed personalised blood tests that can show early on whether the treatment had worked and whether any cancer was still present in the bloodstream.
Dr Kai-Keen Shiu, Chief Investigator of the trial from 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 personalised 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."
Bowel cancer is the fourth most common cancer in the UK, with around 44,000 cases a year. Though still predominantly a cancer that affects older people, cases among the under 50s have been increasing in recent decades.
Like many cancers, if bowel cancer is caught early, the chances of a positive outcome are high. Nine in ten patients treated for stage one bowel cancer survive for five years or more, but specific sub-types of tumours don't respond as well to treatment and are more likely to return. Five-year survival falls to 65% in stage three and 10% in stage four bowel cancer.
The NEOPRISM-CRC trial saw 32 patients recruited with stage two or three bowel cancer and a certain genetic profile (MMR deficient/MSI-high bowel cancer) from five hospitals around the UK. Around 10-15% of patients with stage two or three bowel cancer have this particular genetic make-up, which represents around 2,000-3,000 cases per year in the UK.
Patients were given up to nine weeks of pembrolizumab prior to bowel surgery, instead of the usual treatment of surgery followed by three to six months of chemotherapy, then monitored over time.
The ongoing trial's latest work outlined this month at AACR in San Diego, California, was led by UCL and UCLH, with University Hospital Southampton, St. James's University Hospital in Leeds and the Christie NHS Foundation Trust in Manchester involved in recruiting patients and providing valuable translational samples. All translational work was done by UCL and biotechnology company Personalis.
Professor Marnix Jansen, a clinician scientist and consultant histopathologist who is leading the translational research on the trial from 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 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 personalised blood tests. When tumour 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 tumour 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's story
UCLH patient Christopher Burston was diagnosed with bowel cancer in February 2023 after taking part in routine screening. He had been completing the bowel screening kits sent by post for several years when one returned a positive.
Christopher, 73, of 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 couple of weeks after diagnosis, his oncologist suggested he might be suitable for the NEOPRISM clinical trial testing immunotherapy before surgery. Despite the need to travel to London for treatment, he decided to take part and was referred to UCLH for his care.
He received three doses of immunotherapy over nine weeks, followed by surgery in May 2023. He experienced minimal side effects and recovered well after spending a week in hospital.
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."
Over three years later, he remains cancer-free and has since returned to normal activities, attending 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."
