NEOPRISM-CRC Study Shows Immunotherapy Success in Bowel Cancer Patients

A groundbreaking clinical trial has revealed that patients with a particular form of bowel cancer remain free of recurrence nearly three years after receiving immunotherapy before undergoing surgery. The remarkable finding comes from the NEOPRISM-CRC study led by researchers at UCL and UCLH.

The trial, which is set to be presented at the American Association for Cancer Research Annual Meeting in April 2026, builds on earlier results that showed a significant reduction in tumor size after nine weeks of treatment with the immunotherapy drug pembrolizumab. A staggering 59% of patients had no detectable signs of disease following this initial course of treatment and subsequent surgery.

A crucial aspect of the study's findings is that none of the treated patients experienced a return of their cancer within the observed timeframe, which spanned an impressive 33 months. This outcome applied to both patients who showed no residual cancer after treatment and those with small amounts of disease remaining. Importantly, in the latter group, the remaining cancer did not progress or spread during follow-up.

The trial's results are particularly noteworthy when compared to standard treatment approaches for bowel cancer. Typically, around 25% of patients receiving surgery followed by chemotherapy experience a relapse within three years. The NEOPRISM-CRC study suggests that administering immunotherapy before surgery may offer more sustained cancer control for this specific type of bowel cancer than the conventional combination of surgery and post-operative chemotherapy.

The implications of these findings are significant, as they indicate a potential game-changer in the treatment of bowel cancer. However, further research is needed to confirm the trial's results and explore their broader applicability to patients with similar conditions.

Researchers delved deeper into the trial's success by analyzing blood samples to understand why immunotherapy proved so effective and identify potential biomarkers for predicting patient responses.

The study led to the development of personalized blood tests designed to detect whether treatment had taken hold and if residual cancer cells remained in the bloodstream, providing a crucial indicator of treatment efficacy.

Dr. Kai-Keen Shiu expressed optimism about the trial's findings, stating that the absence of cancer recurrence after nearly three years of follow-up is an encouraging sign that pembrolizumab is a safe and highly effective treatment for high-risk bowel cancers.

Researchers are now exploring the possibility of using immune profiling and personalized blood tests to predict which patients will respond well to immunotherapy. This approach could help tailor treatment strategies, identifying those who require minimal therapy before and after surgery versus those at higher risk of disease progression or relapse.

Bowel cancer remains a prevalent condition in the UK, with approximately 44,000 new cases diagnosed annually, making it the fourth most common type of cancer in the country.

Bowel cancer is a complex condition that requires early detection for optimal treatment outcomes. Research has shown that patients diagnosed with stage one bowel cancer have significantly better survival rates than those diagnosed at later stages. While nine in ten people treated for stage one bowel cancer can expect to live for at least five years, the prognosis worsens as the disease advances.

Some types of bowel cancer are more challenging to treat and are more likely to recur after initial treatment. Specifically, tumors with certain genetic profiles tend to be less responsive to conventional therapies. This is particularly true for patients with stage two or three bowel cancer who have a specific genetic makeup characterized by MMR deficiency and high microsatellite instability.

Researchers at the University of London and other UK institutions have been conducting trials to explore new treatment approaches for this subset of patients. The NEOPRISM-CRC trial, which enrolled 32 participants from five hospitals across the UK, aimed to investigate the efficacy of immunotherapy in combination with surgery. Participants received pembrolizumab before undergoing bowel surgery.

The genetic profile of MMR deficiency and high microsatellite instability is relatively rare among patients with stage two or three bowel cancer, affecting around 10-15% of this group. In the UK alone, this translates to approximately 2,000-3,000 new cases each year. The NEOPRISM-CRC trial aimed to determine whether immunotherapy could improve outcomes for these patients.

Personalized blood tests were used in conjunction with pembrolizumab treatment as part of the ongoing trial. Researchers from UCL and biotechnology company Personalis collaborated on this aspect of the study, which involved analyzing translational samples from various hospitals across the UK.

The study's findings have provided crucial insights into why immunotherapy is effective in treating bowel cancer. Researchers discovered that changes in tumor DNA in the bloodstream closely mirrored patients' responses to treatment.

When tumor DNA disappeared from a patient's blood, it was a strong indicator that they had no remaining cancer. This association highlights the potential of personalized blood tests to monitor treatment effectiveness and predict outcomes.

The study also found that immune profiling from tumor tissue before treatment can help forecast how well a patient will respond to immunotherapy. This information could be used to guide treatment decisions in a more practical and timely manner.

Christopher Burston, a UCLH patient diagnosed with bowel cancer after routine screening, is one of the individuals who have benefited from this research.

Christopher Burston was diagnosed with bowel cancer after a routine screening revealed blood in his stool. Further tests confirmed the presence of a cancerous tumor in his colon.

His oncologist suggested that he might be eligible for the NEOPRISM clinical trial, which was investigating the effectiveness of immunotherapy before surgery. Despite having to travel from Portland, Dorset to London for treatment, Christopher chose to participate and was referred to University College Hospital (UCLH).

Over a period of nine weeks, Christopher received three doses of immunotherapy, which had a significant impact on his condition. He reported experiencing few side effects during this time.

The surgery that followed in May 2023 revealed that the cancer had largely disappeared, with doctors describing it as having "melted away". This was a direct result of the immunotherapy treatment, which appeared to have an almost immediate effect.

Since then, Christopher has made a full recovery and returned to his normal activities. He continues to attend regular follow-up appointments, but more than three years on from his diagnosis, he remains cancer-free.

After undergoing immunotherapy treatment, a patient's bowel cancer appeared to melt away, leaving doctors stunned by its effectiveness.

Regular follow-up appointments have continued to show that the cancer remains in remission, with the individual now over three years since diagnosis without any signs of recurrence. This remarkable outcome has sparked hope for those suffering from similar conditions. The case highlights the potential benefits of immunotherapy as a treatment option.