Gene therapy to block the blood supply to tumors could provide a promising new strategy for treating pancreatic cancer, Chinese scientists said on Tuesday.

In test tube experiments and studies in mice they found the therapy suppressed the formation of new blood vessels, cutting off the nutrient supply needed to grow and spread in the body, although it had little direct effect on the cancerous cells.

In a report in the journal Gut, Dr Yao-Zong Yuan, of Shanghai Second Medical School, said although more research was needed “gene therapy may be a potent strategy to treat many malignant tumors, including pancreatic cancer”.

Pancreatic cancer is an extremely difficult cancer to treat because often by the time it is diagnosed it has already spread in the body.

About 216,000 new cases are diagnosed worldwide each year. Surgery is the most effective treatment but the majority of patients die within one year of diagnosis.

The Chinese scientists inserted a gene that produces a protein called vasostatin into a virus, or vector, to deliver it to the cancerous cells.

In the test tube experiments, 72 hours after the cancerous cells were infected with the genetically modified virus the scientists said vasostatin was active. The gene therapy also curbed the growth of pancreatic tumors in the mice.

The causes of pancreatic cancer, which usually occurs in people over 60 years old, are unknown. About 30 percent of cases are attributable to smoking.