Zero Relapses in 32 Bowel Cancer Patients Treated Before Surgery

None of 32 patients in a UK bowel cancer trial had a reported recurrence through 33 months of follow-up after a short immunotherapy course before surgery, researchers reported. ^[2]

The patients had stage two or three cancer and tumours with a particular genetic profile. They received pembrolizumab for up to nine weeks before their operations, in a regimen designed to avoid the usual three to six months of chemotherapy after surgery. ^[1][2]

The result held even among participants whose treatment left small amounts of cancer, according to the research team. Earlier results found no detectable disease after pembrolizumab and planned surgery in 59% of participants. Now, the longer follow-up offers an encouraging finding beyond that initial response: no reported relapses across the whole group. ^[1][2]

The trial, called NEOPRISM-CRC, was led by University College London and University College London Hospitals. Its follow-up findings were presented at the American Association for Cancer Research annual meeting in April 2026, with a further account published on October 10. ^[1][2]

For Christopher Burston, a participant diagnosed with stage three bowel cancer, the response was memorable. He recalled doctors saying the cancer had "melted away". He received three doses over nine weeks before surgery in May 2023 and said he remains cancer-free while attending follow-up appointments. ^[1][2]

Surgery remained part of his treatment, as it did in the trial's planned regimen. The achievement was to bring immunotherapy forward, before the operation, and avoid the usual post-operative chemotherapy. ^[1][2]

A small group with a striking result

The trial recruited patients at five UK hospitals. Alongside UCLH, University Hospital Southampton, St. James's University Hospital in Leeds and the Christie NHS Foundation Trust in Manchester recruited participants and supplied samples. ^[1][2]

All 32 patients had tumours described as mismatch-repair-deficient, or MMR-deficient, or as having high microsatellite instability, known as MSI-high. These terms identify the genetic subgroup studied. According to UCL, about 10% to 15% of people with stage two or three bowel cancer have this profile, equivalent to an estimated 2,000 to 3,000 cases each year in the UK. ^[2]

That is a minority of patients, but a substantial group for whom a shorter treatment course could matter. The trial's promise lies in matching a drug to that tumour profile, rather than treating bowel cancer as a single disease with a single answer.

The researchers set the results against an estimate that about 25% of patients receiving standard surgery and post-operative chemotherapy relapse within three years. The trial's 33-month follow-up approaches that time frame, making the absence of recurrence striking. ^[1][2]

That comparison was not a randomised control group. With only 32 participants, the trial does not prove a cure or establish that this approach should replace standard care. The material provided does not establish publication of the follow-up in a peer-reviewed journal. ^[1][2]

Releasing the immune system's brake

Pembrolizumab is an immune checkpoint inhibitor. Drugs in this class interfere with signals that restrain T cells, immune cells capable of attacking cancer. The PD-1/PD-L1 checkpoint is one such signalling system, according to the US National Cancer Institute. Blocking it can allow T cells to attack tumour cells. ^[3]

The treatment therefore works through the patient's immune response. In this trial, researchers gave it while the bowel tumour was still present, before the planned operation, rather than following the usual sequence of surgery and then chemotherapy. ^[1][2]

Burston's experience puts that schedule into human terms: three doses across nine weeks, followed by an operation. His account began with a positive screening test and a stage three diagnosis, then travel to London for treatment. ^[1][2]

The phrase he recalled from his doctors captures the visible response. The follow-up measures something harder to achieve: whether cancer returns after treatment. Both matter. A tumour disappearing is an immediate success, while a sustained absence of relapse is what patients need the treatment to deliver.

Immunotherapy also carries risks. Checkpoint inhibitors can cause rash, diarrhoea and fatigue. They can sometimes trigger inflammation in organs including the colon, lungs, liver or heart, according to the National Cancer Institute. These are risks of the drug class, rather than reported outcomes for these 32 patients. ^[3]

A shorter course is attractive, but weeks of treatment alone cannot measure its burden. Any decision to change care must weigh cancer control alongside the harms caused by treatment.

Finding who can receive less treatment

The researchers are also examining whether blood and tissue tests can help identify who responds. They studied blood samples and reported that the disappearance of tumour DNA from the blood was associated with having no cancer remaining. ^[1][2]

They also said that examining the immune features of tumour tissue before treatment may help predict response. Both approaches remain research tools with potential future uses in guiding treatment. ^[1][2]

The practical ambition is precise: identify patients likely to benefit from immunotherapy and judge how much further treatment they need. A test that reliably answers those questions could make a shorter regimen easier to use with confidence.

For now, the next work described by the team is to develop those blood-based and tumour-profiling approaches, while follow-up tracks whether the patients' freedom from recurrence lasts. Burston continues to attend his follow-up appointments. ^[1][2]