A short course of immunotherapy is highly effective in treating a particular group of colon cancer patients, according to research carried out by the Netherlands Cancer Institute and published in the New England Journal of Medicine.

The treatment, which consisted of two cycles of immunotherapy before surgery, was effective in almost all patients and two third of patients no longer had any live tumor cells at the time the surgery took place.

The patients had colon cancer with a specific genetic makeup, known as mismatch-repair deficient (dMMR) or microsatellite instable (MSI).

“This specific type of colorectal cancer contains a high number of DNA errors, which means that the tumor cells are more easily detected by the immune system. The immune system only requires a small incentive to successfully target the tumor cells,” oncologist Myriam Chalabi said.

None of the patients had developed metastases in the average of two years that they have been followed since undergoing treatment.

“We wanted to investigate what immunotherapy could do for people with non-metastatic colon cancer,” she said. “We witnessed something that rarely ever happens: every single patient in the study responded well to the new treatment.”

The treatment is not yet available for patients although this is the aim of the trial. “Towards the end of the year, we will have followed these patients for three years. If the majority of these patients are still cancer-free, we should work towards making this therapy a standard treatment option,” she said.