People suffering from pancreatic cancer should be switched to a new drug regime that almost doubles their chance of survival, researchers say.
Combining two chemotherapy drugs available on the NHS boosted the number of patients alive following surgery to remove their tumour, according to a new Cancer Research UK study.
Experts hope the drugs may also help people in more advanced stages of the cancer, which kills almost 9,000 people in the UK every year.
Pancreatic cancer has very poor survival rates, with only a fifth of all people still alive after a year and just 5% alive five years after diagnosis
Surgery is usually the only way to cure the cancer but it is only suitable for around 10% to 15% of people.
In the new study, presented at the American Society of Clinical Oncology (ASCO) conference in Chicago, 732 patients who had undergone surgery to remove their tumour were divided into two groups.
The first received the chemotherapy drug gemcitabine (Gemzar) - the standard treatment for pancreatic cancer - while the other half received a combination of gemcitabine and capecitabine (Xeloda).
The results showed that around 85% of people given both drugs were still alive after one year - described as "unusual" for pancreatic cancer by the head of the trial, Professor John Neoptolemos, from the University of Liverpool.
Almost 60% of patients were still alive after two years while impressive results were also seen after five years.
Almost a third (29%) of patients given the drug combination lived at least five years compared with only 16% given gemcitabine alone.
Prof Neoptolemos said the results were "overwhelmingly good" and patients should be switched to the new regime, which will be low cost to the NHS.
He added: "In the 1970s and 80s, people said you shouldn't operate on pancreatic cancer because it was a waste of time to treat these patients at all.
"In the space of 20 or 30 years, we've made a huge leap.
"This shows us it is a tumour we can get our head around."
Prof Neoptolemos, who is the clinical lead for new guidelines which are currently being drawn up by the National Institute for Health and Care Excellence (Nice), said there may be a wider use for the drugs to treat pancreatic cancer that has spread around the body.
He said: "The pancreatic cancer community will definitely think about this. If we look at metastatic setting, if there is an improvement it will be a small one. But it will lead to a re-thinking of the way we use chemotherapy drugs in pancreatic cancer.
"The view has been that chemotherapy doesn't work in pancreatic cancer but this shows we shouldn't close the door on chemotherapy."
A further clinical trial is now underway to see if the drug combination can help shrink tumours in people whose pancreatic cancer is considered to be borderline for surgery.
If their tumours can be shrunk, these patients may be suitable for surgery, which would significantly boost their chances of survival.
Prof Peter Johnson, Cancer Research UK's chief clinician, said: "Nearly 10,000 people are diagnosed with pancreatic cancer each year in the UK and it remains a very difficult disease to find and treat."
Alex Ford, chief executive of Pancreatic Cancer UK, said: "These are incredibly exciting results from a major trial for those diagnosed with this dreadful disease.
"We now need to see these results quickly translate to a change in approach by clinicians so that patients start to benefit more widely straight away. "
A spokesman for Nice said the combination therapy is currently used off-label in clinical practice but it would take account of the new trial in its upcoming guidelines.