Every participant in a bowel cancer immunotherapy trial remained cancer-free nearly three years after receiving pembrolizumab prior to surgery, indicating promising results for future treatments.
In a groundbreaking study led by researchers at University College London (UCL) and UCL Hospitals, all participants in a trial for bowel cancer immunotherapy remained cancer-free nearly three years after receiving the experimental drug pembrolizumab before their surgeries.
The trial focused on 32 patients diagnosed with stage 2 or 3 bowel cancer, specifically those with tumors exhibiting a genetic profile known as MMR-deficient or MSI-high. This particular profile, which is present in approximately 10% to 15% of bowel cancer cases, indicates a faulty DNA repair system within the body. Researchers hypothesized that this genetic vulnerability could make it easier for immunotherapy drugs to target and attack the tumors effectively.
Rather than following the conventional treatment route of chemotherapy after surgery, these patients were administered pembrolizumab for a duration of up to nine weeks prior to their operations. Early data from the trial revealed that the drug was remarkably effective, shrinking tumors to the extent that 59% of patients exhibited no signs of cancer by the time they underwent surgery.
Recent follow-up data has confirmed that 33 months post-treatment, none of these patients have experienced a recurrence of the disease. This includes individuals who had small traces of cancer remaining after surgery, which did not grow or spread again.
Dr. Kai-Keen Shiu, the chief investigator and a consultant medical oncologist at UCLH, expressed optimism regarding the findings. “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,” he stated.
In contrast, the traditional approach of surgery followed by chemotherapy sees about 25% of patients with this genetic profile experiencing a cancer recurrence within three years, according to the study’s findings.
The research team also implemented personalized blood tests to monitor the patients throughout the trial. These tests detect tiny fragments of tumor DNA in the bloodstream, enabling doctors to assess the effectiveness of the treatment prior to surgery. “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,” noted Yanrong Jiang, the first author of the study and a clinical PhD student at the UCL Cancer Institute.
Despite the promising results, the researchers acknowledged certain limitations of the study. The trial was relatively small, involving only 32 participants, and it focused on a specific genetic subset of patients, which may limit the applicability of the results to the broader bowel cancer population. Additionally, the team emphasized the need for extended follow-up to ensure that cancer does not return in the future.
Nonetheless, the researchers remain optimistic about the potential for personalized care in cancer treatment. “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 remarked. “These tools could help us tailor our approach, identifying patients who are doing well and may need less therapy before and after surgery.”
The results of this promising study were presented at the American Association for Cancer Research (AACR) Annual Meeting 2026 held in San Diego last month, highlighting the ongoing advancements in cancer treatment and the potential for improved patient outcomes.
According to UCL, the findings underscore the importance of continued research in immunotherapy and personalized medicine for cancer patients.