Canadian research, focused on Hodgkin's Lymphoma, a cancer of the immune system which affects mainly young men, has identified the particular chemical which allows tumour cells to multiply rapidly.

When the chemical was removed, the cancer cells simply stopped growing.

Most Hodgkin's patients are treated with chemotherapy, radiotherapy or a combination of the two.

Scientists found that Interleukin-13, a growth factor, is released by Reed-Sternberg cells, which are the typical cancer cells found in Hodgkin's patients.

Prompts cells to multiply

It appears to be the chemical signal for the Reed-Sternberg cells to reproduce, making the tumour larger and increasing the risk of the cancer spreading.

An examination of genes taken from 950 tumours found IL-13 present in most.

Chemotherapy can have dangerous long term effects

Dr Tak W. Mak, senior scientist at the Ontario Cancer Institute, said: "I'm particularly excited because for the first time we have identified the engine that drives at least some Hodgkin's cancer cells to multiply.

"We are now working to find a way to shut down that engine. These findings have huge clinical potential."

Test tube experiments found that tumour cells deprived of their supply of IL-13 simply stopped growing.

Gene technology may now be the way to deal with or block Interleukin-13 production from cancer cells.

Dr Ursula Kapp, from the University Medical Centre in Freiburg, Germany, said: "Now we know IL-13 plays a major role in the growth of at least some Hodgkin's tumours, we can begin to look at new treatments using IL-13 neutralising antibodies or by blocking IL-13 production altogether within Reed-Sternberg cells."

Side effects are dangerous

An alternative, particularly to chemotherapy for Hodgkin's is desirable, particularly as doctors are uncovering long term effects of the powerful treatments used to kill cancer cells, which can be as dangerous as the initial disease itself.

Although the cure rate for Hodgkin's is around four in five, a significant number of patients are falling prey to other cancers, heart disease or, more usually, infertility.

Hodgkin's is a cancer which is often found in people in their 20s and 30s, and affects, in the first instance, tissue of the lymphatic system in the neck, armpits, chest and groin.