Bowel cancer “melted away” after immunotherapy, then stayed away
A short course of immunotherapy before surgery may offer remarkably durable protection for some patients with stage two or three bowel cancer. In the NEOPRISM-CRC trial, 32 patients with a specific genetic form of bowel cancer received pembrolizumab for up to nine weeks before surgery instead of the usual post-surgery chemotherapy. After nearly three years of follow-up, none of the patients had experienced a cancer…
Key points
- Patients with MMR deficient/MSI-high bowel cancer remained cancer-free for 33 months after pembrolizumab before surgery.
- 59% of trial patients had no detectable disease after pembrolizumab and planned surgery.
- Personalized blood tests and immune profiling may predict treatment response and guide therapy.
Patients with a specific form of bowel cancer remained free of recurrence for almost three years after receiving a short course of immunotherapy before surgery, according to new findings from the NEOPRISM-CRC clinical trial led by researchers at UCL and UCLH. The results are due to be presented at the American Association for Cancer Research (AACR) Annual Meeting 2026 in April.
The trial enrolled 32 patients with stage two or three bowel cancer and a particular genetic profile (MMR deficient/MSI-high bowel cancer) at five hospitals across the UK. Earlier data showed that 59% of patients had no detectable signs of disease after nine weeks of treatment with pembrolizumab before their planned bowel cancer surgery.
Durable cancer control
After 33 months of follow-up, none of the patients treated in the trial had experienced a return of their cancer. That was true both for patients who had no signs of cancer after treatment and for those who still had small amounts of disease remaining; in the latter group, the remaining cancer did not grow or spread during follow-up.
By comparison, around 25% of patients treated with the standard approach of surgery followed by chemotherapy are expected to relapse within three years. The findings suggest that giving a short course of immunotherapy before surgery may provide more durable cancer control for this specific type of bowel cancer than the usual combination of surgery and post-operative chemotherapy.
The outcome of the surgery was essentially that the cancer had melted away, these were the doctor's words.
— Christopher Burston
Predicting treatment response
Researchers also studied blood samples to investigate why the treatment worked so well and to find ways of identifying which patients were most likely to benefit. They developed personalized blood tests designed to show early whether treatment had worked and whether traces of cancer were still circulating 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."
