Cancer patients with one of the most lethal forms of the disease have had their lives prolonged by a vaccine developed in New York.

Cancer of the pancreas kills 95 per cent of sufferers within two years. In a preliminary trial patients who received the vaccine survived twice as long on average.

Of the 10 patients treated, one was still alive and free of the disease five years on, with two alive and disease-free after two years. Typically, patients survive 14-15 months after surgery for this cancer. The pancreas produces enzymes and insulin essential for digestion in the gut.

Researchers, who presented the findings to the European Cancer Conference in Copenhagen yesterday, emphasised they could not yet tell if the vaccine would work on all patients.

Dr Robert Maki, of the Memorial Sloan-Kettering Cancer Centre in New York, said: "The finding of even a few patients surviving two or more years is promising. However, and this is a big however, we may be biased in who we selected for the study. Perhaps, ... we got a few people who were destined to do well."

Confirmation of the findings would have to await the results from a proper randomised controlled trial, he said.

All the study subjects had their cancer removed by surgery. The vaccine, based on a protein, HSPPC-96, was then prepared from the patient's tumour, and administered within eight weeks of surgery.

None had side-effects from the vaccine and none had chemotherapy or radiotherapy. Dr Maki said that a better picture of the vaccine would emerge from the clinical results of a larger study.

HSPPC-96 has already been shown to have dramatic effects in some patients with melanoma, the most serious form of skin cancer. It is also being tested as a vaccine against kidney cancer.

The conference was told that deaths from prostate cancer, the commonest cancer in men, are falling in America and Europe due to early detection and treatment. Professor Sir Richard Peto of Oxford University said that new figures showed prostate cancer deaths in men aged 50-74 fell by one third between 1990 and 2000, and by one quarter in men aged 75-84.