By Caroline Ryan
BBC News Online health staff in Copenhagen
Scientists say they have taken the first steps towards developing a vaccine against pancreatic cancer.
The vaccine takes proteins from the patient's tumour
Virtually all patients who develop the cancer die, the majority within two years if being diagnosed.
The US researchers created a vaccine using proteins from the patient's own tumour.
But they told the European Cancer Conference in Copenhagen more research was needed before a vaccine for all patients could be developed.
There are almost 7,000 cases of the cancer in the UK each year.
Researchers from the Memorial Sloan-Kettering Cancer Center in New York carried out an initial study on 10 patients with pancreatic cancer.
They created personalised vaccines using a heat-shock protein (HSP) which helps cells rebuild after they have been attacked.
A tumour cell would have HSPs stuck to cancer proteins, so a HSP vaccine using protein HSPPC-96 would prompt the patient's immune system to attack cells containing the proteins stuck to the HSPs wherever they were in the body.
The greatest number of HSP proteins are in the tumour itself, so targeting them will kill the cancer.
There were problems creating an effective vaccine because the pancreas makes digestive enzymes that destroy proteins, so the tumour cells initially destroyed the vaccine.
But the scientists developed a method of purifying the vaccine so that it could be administered.
Each patient underwent surgery to remove their tumours. They were then vaccinated within eight weeks of the operation.
The study found two patients were alive and disease-free after two years and one more was alive and unaffected by the cancer five years after being vaccinated.
The average typical survival after surgery for pancreas cancer is 14 to 15 months.
However, the researchers stressed the research was still at a very early stage, and much more work was needed on many more patients before it would be possible to say if a vaccine could be developed to be used on all pancreatic cancer patients.
Dr Robert Maki, who led the research, said: "Over 95% of people with pancreatic cancer die, typically within two years of diagnosis, and mortality is still about 90% even for those who have complete removal of their pancreatic cancer.
"So the finding of even a few patients surviving two years or more is promising regarding the usefulness of this vaccine after removal of the cancer.
"However, and this is a big however, we may be biased in who we selected for the study. Only people who could have an operation were eligible; we screened out people who had evidence of spread of tumour before they entered the study. Perhaps, just by chance, we got a few people who were destined to do well.
The HSP has also been shown to skin cancer, and researchers are also looking to see if it can be used as the basis of a vaccine against kidney cancer.
Dr John Toy, medical director of Cancer Research UK, told BBC News Online: "This small study reports a further effort in this area of research.
"It describes mildly encouraging results, but it is possible that just by chance a few of the people selected for the study were destined to do well - that is, without the vaccine - and a proper randomised study is required to determine whether this vaccine could, indeed, truly prove to be useful.