The trial, published in the scientific journal Nature on Wednesday, found that half of patients who had been treated with a personalized mRNA cancer vaccine following surgery did not experience recurrence of their tumours 18 months later.

The vaccine led to the development of T cells that taught their immune systems how to recognize and fight off cancer growth.

In discussing the early-stage trial's results, Drew Weissman said, “I am very supportive of the findings. it is not a definitive proof-for-use study. Larger studies are needed to determine effectiveness.”

Vinod Balachandran, a cancer surgeon at Memorial Sloan Kettering Cancer Center who led the study, said that he and his colleagues planned to conduct more extensive tests.

“I think it’s definitely very encouraging to see that [an immune] response correlates with recurrence-free survival,” the surgeon said.

“However, it is a small study with only 16 patients in phase one. So it is a correlation. It’s not causation. We do have to test causation in a larger clinical trial.”

Pancreatic cancer has a high mortality rate and is one of the most aggressive forms of cancer. Surgery is the main form of treatment, but patients often face recurrence 90 percent at seven to nine months later on.

Doctors believe that chemotherapy is only partially successful at delaying cancer recurrence. However, other types of treatments, such as immunotherapy, are not believed to work well at all.