A new treatment which trains the immune system to attack cancer has shown "extraordinary" results - and could be a potential breakthrough in curing the disease.

In one study 94% of patients with acute lymphoblastic leukaemia saw their symptoms vanish completely.

And patients with other blood cancers saw response rates of more than 80%, with half experiencing complete remission.

Lead scientist Professor Stanley Riddell, from the Fred Hutchinson Cancer Research Center in Seattle, said: "Most of the patients in our trial would be projected to have two to five months to live.

"This is extraordinary. It's unprecedented in medicine to be honest, to get response rates in this range in these very advanced patients."

The treatment involves removing immune cells called T-cells from patients, tagging them with "receptor" molecules that target cancer and then infusing them back in the body.

So far, the technique has only been tried on patients with "liquid" blood cancers.

Prof Riddell hopes to progress to patients with solid tumours, but points out that this will be challenging.