Explainers
Immunotherapy trial: bowel cancer stayed away 33 months
A small trial found that nine weeks of pembrolizumab before surgery left patients with no cancer recurrence after nearly three years.
A trial presented this month at the American Association for Cancer Research annual meeting in San Diego found that 32 patients with stage two or three bowel cancer who received immunotherapy before surgery had no cancer return after 33 months of follow-up.
The NEOPRISM-CRC trial, led by University College London and University College London Hospitals, enrolled patients whose tumors have a specific genetic profile: MMR deficient or MSI-high bowel cancer. About 10 to 15% of people with stage two or three bowel cancer have this profile, which equals roughly 2,000 to 3,000 cases each year in the UK.
Patients received up to nine weeks of pembrolizumab before their planned bowel surgery, instead of the standard treatment of surgery followed by three to six months of chemotherapy. The initial results, reported earlier, showed that 59% of patients had no detectable signs of disease after the drug treatment and before surgery.
After 33 months, none of the patients had a recurrence. That held true both for patients whose cancer had disappeared after the immunotherapy and for those who still had small amounts of disease left — in the latter group, the remaining cancer did not grow or spread.
By comparison, about 25% of patients treated with the standard approach of surgery followed by chemotherapy are expected to have a relapse within three years.
Researchers also developed personalized blood tests to track tumor DNA in the bloodstream. Disappearance of tumor DNA from the blood was strongly linked to having no cancer remaining. Immune profiling of tumor tissue before treatment also helped predict which patients would respond.
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."
He added that the personalized blood tests and immune profiling could help tailor treatment — identifying patients who are doing well and may need less therapy, versus those at higher risk who need additional treatment.
Bowel cancer is the fourth most common cancer in the UK, with about 44,000 new cases each year. Five-year survival is about 90% for stage one, 65% for stage three, and 10% for stage four.
One patient, Christopher Burston, 73, of Portland, Dorset, was diagnosed with stage three bowel cancer in February 2023 after a routine screening test came back positive. He received three doses of pembrolizumab over nine weeks before surgery in May 2023. His surgeon told him the cancer had "melted away." More than three years later, he remains cancer-free.
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