A small but striking clinical trial has reported that giving immunotherapy before surgery for a specific type of bowel cancer led to zero recurrences nearly three years later. The finding challenges the traditional approach of operating first and could transform care for patients with a particular genetic makeup. For a disease that is the second leading cause of cancer deaths worldwide, the result offers a rare and hopeful signal.
The trial, known as NEOPRISM-CRC, focused on patients with stage two or stage three colorectal cancer who carry a genetic signature called MMR-deficient or MSI-high. These tumors are packed with mutations, making them easier for the immune system to recognize once activated. This subtype accounts for about 10 to 15 percent of bowel cancers. Instead of the standard sequence of surgery followed by months of chemotherapy, researchers gave 32 patients three doses of pembrolizumab over nine weeks before surgery. Pembrolizumab works by removing the natural inhibitory signals that cancer places on immune cells, effectively teaching the body to detect and fight tumors.
The results were striking. After 33 months of follow up, not a single patient had seen their cancer return. Even in cases where small traces of cancer remained after surgery, the disease did not grow or spread. By comparison, under standard care, about a quarter of similar patients typically see their cancer return within three years. The research team also developed personalized blood tests capable of detecting tiny fragments of tumor DNA in the bloodstream. When this DNA disappeared, it was a strong signal that the cancer had been cleared at a deeper level. More than half of the patients showed no detectable cancer after treatment and surgery, and none required standard post-operative chemotherapy.
What This Means for Patients
The idea of delaying surgery in favor of early immunotherapy challenges a long-standing medical instinct. If these findings hold up in larger studies, the approach could allow some patients to avoid chemotherapy altogether, sparing them months of side effects without compromising outcomes. The researchers also analyzed tumor samples to study immune activity before treatment, identifying patterns that may help predict who will respond best. “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,” said Kai-Keen Shiu, an oncologist at University College London Hospital who was involved in the trial.
The research team now plans to expand the trial to include more patients and to explore whether similar strategies could work in other forms of cancer. For the subset of bowel cancer patients with the MMR-deficient signature, the path forward looks increasingly hopeful. As one 73 year old patient who remains cancer free more than three years after treatment put it, the immunotherapy had an almost immediate effect, and the cancer had essentially melted away.