A new cancer treatment procedure has been discovered that could pave the way to a day when doctors are able to train a person’s T-cells in their blood stream to fight cancer cells.

On Wednesday, researchers in the United States reported on the result of an experiment they conducted on nine cancer patients who had advanced melanoma that had already spread to other parts of the body.

They extracted blood from each of the patients, separated the white blood cells, and caused them to memorize the cells that cause cancer. When the cells were injected back into the body, the cells that were trained in the lab can destroy tumor cells for more than one year.

In this preliminary experiment, the “killer” T-cells weren’t able to stop the cancer progression in the majority of the patients, but in one, the cancers shrank to such a point in two years’ time that they couldn’t be seen on medical scans.

The testing and procedure development for this type of treatment is still in the early stages, but the general hope is that in five to ten years, this type of experimental therapy could become the norm and become an approved form of cancer treatment for mass usage.