New drug offers hope of revolution in cancer therapy

Scientists are testing a revolutionary cancer drug and radiation therapy that has cured tumours in mice and could lead to long-term cures in humans.

The two-pronged treatment using combretastatin will be tested on humans next year. Scientists who tested it on human tumours grown on genetically engineered mice found that the cancer entirely disappeared in most cases.

Tumours were completely eradicated in 85 per cent of the animals in a pre-clinical study and there was no evidence of any residual cancer nine months later.

The therapy could work on most cancers, including cancer of the breast.

Professor Richard Begent, head of oncology at the Royal Free Hospital, London, where scientists have carried out the work for the Cancer Research Campaign, described the drug as "exciting" and said the combination therapy cured cancers in animals with just a single treatment.

Combretastatin, derived from the bark of the African bush willow, has been used to treat cancer patients before. But while the drug has killed off cancerous cells, it has not prevented them from growing back after a few months.

The key to the new technique is to combine the drug with radiation therapy, using anti-bodies tagged with radioactive "warheads".

Combretastatin works by cutting off the blood supply to cancerous cells. Cancer tumours rely on a blood supply and create a special network of capillaries as they grow.

The drug binds on to the dividing cells creating the capillaries, destroying the blood supply.

Cancer Research Campaign scientists who began studying combretastatin four years ago found it killed up to 95 per cent of cells in solid tumours in the laboratory. But tumours grow back because the remaining small number of cells at the outer edge of the tumour feed on normal blood vessels, which are not destroyed by the combretastatin. The antibodies kill these cells "from the inside" by radiation.

Professor Begent said: "Combretastatin has been given to patients on its own before but the response has not been very good. In most cases, the cancer continues to grow.

"But when you put the two treatments together it's then possible in these animals to cure the cancer completely with just a single treatment. It is rather exciting and we are now working towards carrying out some clinical trials."

Doctors believe that if the clinical trials are successful, the combination therapy could be available within five years.

The dramatically successful trials by a team of British scientists have been under way at the Royal Free Hospital and the Gray Laboratory Cancer Research Trust, at Mount Vernon Hospital in Northwood, Middlesex. Experiments at the Royal Free were headed by Dr Barbara Pedley, head of tumour biology at the CRC targeting and imaging group.

Although work has so far concentrated on colorectal cancer using tumours grown on genetically engineered mice, scientists say the drug works on a wide range of cancers.

Combretastatin, also known as CA4P, was initially developed by scientists from the Cancer Research Campaign with the backing of the American company OXiGENE.