The drug, known as deoxycoformycin (DFC), is used to treat people with 'hairy cell' leukaemia, of which there are about 100 new cases each year in the United Kingdom.
The results of a five-year trial at the Royal Marsden Hospital in south-west London were presented to the Congress of the International Society of Haematology in London yesterday.
Professor Daniel Catovsky, head of the Institute of Cancer Research's Section of Haematology at the hospital, said that four years after 110 patients were treated with DFC, more than 80 per cent were still free of symptoms and did not require any further chemotherapy.
'The results have been quite staggering,' he said. The patients were given between eight and 12 injections over a period of three to four months.
Professor Catovsky said that 75 per cent of patients had achieved complete remission, and 22 per cent had partial remissions. Only 3 per cent had shown no response.
'After five years in remission, I think we can cautiously talk about cures.
'When one considers that only a few years ago the disease was almost inevitably fatal, this is a remarkable breakthrough,' the professor said.
Hairy cell leukaemia affects five times more men than women, and most victims are aged between 40 and 60 years.
Other treatments - including the drug interferon - have shown promise but relapses occurred in 90 per cent of patients within two years of stopping the treatment.Reuse content