Exclusive: European regulators are reviewing the evidence for a link between diabetes treatments and pancreatic cancer, as a large study looking at UK data found sulphonylureas and insulin were associated with a ‘substantially' increased risk.
In one of the largest analyses to date looking at anti-diabetes drugs and pancreatic cancer risk, the researchers found long-term use of insulin was linked with a doubling of the risk of pancreatic cancer, and sulphonylureas increased the risk by 90%.
The international group of researchers investigated 2,763 patients on the UK General Practice Research Database – average age 70 years - with a first-time diagnosis of pancreatic cancer, and adjusted for confounders including BMI, smoking, alcohol consumption and diabetes duration.
When compared with 16,578 matched controls who did not have pancreatic cancer, patients who had at least 30 prescriptions for sulphonylureas had an increased risk of pancreatic cancer, with an odds ratio of 1.90. Similarly, patients who had at least 40 prescriptions of insulin had an odds ratio of 2.29, compared with controls.
Previous studies have shown that metformin was associated with a decreased risk of overall cancer, and specifically with pancreatic cancer, but this study found no ‘materially altered risk' with the treatment. However, they did find a statistically significant decrease in risk – odds ratio 0.43 - in women who used metformin long-term.
Similarly, the researchers noted that the increased risk of pancreatic cancer with long-term use of sulphonylureas was mainly seen in women, while the increased risk with insulin was mainly attributable to men.
Neither metformin, sulphonylureas or insulin were associated with increased risk of pancreatic cancer when used short-term (between one and nine prescriptions for metformin or sulphonylureas, and between one and 14 prescriptions for insulin).
Study author Professor Chrostoph Meier, head of the pharmacoepidemiology unit and hospital pharmacy at University Hospital Basel, Switzerland, said: ‘Long-term use of sulphonylureas and insulin were both associated with a substantially increased risk of pancreatic cancer.'
An MHRA spokesperson said while insulins and sulphonylureas were an effective treatment for patients with diabetes, an evidence review in France and the Netherlands was ongoing.
He said: ‘A number of studies have examined a possible association between therapies for diabetes and cancer and these data are being reviewed within Europe.'
‘The results of this study will be carefully considered within the context of this review to determine whether they have any implications for prescribing guidance.'
Dr Andrew Brewster, a GPSI in obesity and diabetes in Reading, said: ‘We need to question whether it is the insulin, or the obesity driving the excess risk.'
Anti-diabetes drugs and odds of pancreatic cancer
American Journal of Gastroenterology 2012, published online 31 January