Bowel cancer patients stayed cancer-free for nearly three years after immunotherapy before surgery in a clinical trial.
Researchers found patients with a specific type of bowel cancer showed no sign of the disease returning when they were given immune-boosting drugs before surgery.
The results were described as “extremely encouraging”.
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.
“What is particularly exciting is that we now may be able to predict who will respond to the treatment using personalised blood tests and immune profiling.
“These tools could help us tailor our approach, identifying patients who are doing well and may need less therapy before and after surgery versus patients at higher risk of disease progression or relapse who need additional treatment.”
The study involved 32 patients with stage two or three bowel cancer whose tumours had a genetic profile known as MMR-deficient/MSI-high, accounting for around 10 to 15 per cent of stage two and three cases.
This means the tumour’s DNA repair system is faulty, which can make it more likely to respond to immunotherapy, a treatment that helps the immune system recognise and attack cancer cells.
Instead of the standard approach of surgery followed by three to six months of chemotherapy, patients were given up to nine weeks of the immunotherapy drug pembrolizumab before their operation.
Early results showed the treatment shrank tumours, with 59 per cent of patients having no detectable signs of cancer after surgery.
After 33 months of follow-up, none of the patients had seen their cancer return.
This included those whose cancer had completely disappeared and those who still had tiny amounts remaining after surgery, which did not grow or spread.
Around a quarter of patients receiving standard surgery and chemotherapy would normally be expected to relapse within three years.
Researchers said the findings suggest immunotherapy before surgery could be an effective treatment for bowel cancer.
Alongside the survival results, scientists analysed blood samples to understand why the treatment was so effective and to identify which patients were most likely to benefit.
They developed personalised blood tests that could show whether treatment had worked and whether any cancer remained in the bloodstream.
The trial was conducted by teams at University College London and University College London Hospitals NHS Foundation Trust.
Marnix Jansen, a clinician scientist and consultant histopathologist leading the translational research on the trial from UCL Cancer Institute and UCLH, said: “These results not only confirm the durability of responses we saw almost three years ago, but also provide crucial biological insights into why immunotherapy is so effective in this setting.”
Yanrong Jiang, first author of the latest abstract and clinical PhD student at the UCL Cancer Institute, said: “As a research team, we were thrilled to be able to follow patients very closely using the personalised blood tests.
“When tumour 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.
“In addition, we also saw that immune profiling from tumour tissue, before patients start their first cycle of treatment, can help to predict response.
“We hope these tests may be used to guide treatment decisions in a more practical and timely way.”
