Immune cells taken from a patient - then souped-up in the laboratory - can be injected back to take on the most dangerous form of skin cancer.

Many scientists believe that the body's own defences against foreign intruders can be harnessed to battle malignant melanoma.

However, a team from Nantes in France are believed to be among the first to add immunotherapy to standard surgery.

A group of more than 40 patients with melanoma, which had already spread beyond the initial tumour, were given the treatment.

Three years later, there are signs that the spread of their disease may have at least been slowed by the treatment.

Almost three-quarters of the group given the therapy have not relapsed, compared to 44% in a control group given surgery then another drug which stimulates the immune system.

To find the body's secret weapon, scientists remove cells from a lymph node - a part of the circulation system used by immune cells, but which also often forms a "staging post" for cancer as it spreads around the body.

In this case, the nodes have already been "invaded" by cancer cells, and are being removed by a surgeon in a bid to stop the cancer spreading.

Beefed-up cells

Immune cells called tumour infiltrating lymphocytes (TILs) are extracted, and then grown in the laboratory to increase their numbers and their potency.

These are then injected back again six weeks later, with the aim of producing a specific anti-tumour immune reaction.

The scientists, from the INSERM U 463 laboratories in the French city, certainly found signs that this could happen.

In some patients, the replaced TILs certainly went on to produce more immune cells capable of stimulating an attack on melanoma cells.

However, only those whose melanoma had spread no further than one lymph node appear to be benefiting from the treatment. If the cancer had spread to other lymph nodes, there was no increase in survival.

Professor Brigitte Dreno, who led the research - which was presented at the European Cancer Conference in Lisbon, said: "Our results show that TILs injected as adjuvant treatment at stage III of melanoma, before any relapse, can decrease the frequency of relapses and increase survival of patients."