Fresh data which reinforces the safety profile of Lantus, was unveiled by a new meta-analysis data at the World Diabetes Congress in Dubai, which adds to "the wealth of evidence resulting from more than 80,000 patients enrolled in clinical trials and 38 million patient years of treatment exposure to Lantus (insulin glargine)". The figures are derived from databases as well as from clinical trials and from a case-control study in numerous countries (such as Sweden, Germany, Scotland, England and Taiwan) which assessed the risk for cancer in individuals with diabetes using different insulins.

Peter Boyle, the study's lead investigator and president of the International Prevention Research Institute in Lyon, France, said the meta-analysis "highlights the need to go beyond single study reports and utilise all available data". He added that “in the context of all available information, the current evidence supports that insulin glargine is associated with no increased risk of cancer as compared to other insulin therapies. These findings are reassuring for patients and their physicians."

Sanofi pointed out that it is sponsoring three large Lantus studies, including two retrospective cohort studies and one case-control trial, which are currently being conducted by independent investigators.

The meta-analysis was presented soon after results of a study presented at the San Antonio Breast Cancer Symposium suggested that people who used Lantus had a 2.9-fold greater risk of developing cancer. The research, based on medical records of 23,266 patients in southern Sweden, also found that those taking metformin had an 8% lower chance of developing cancer.

The study is flawed, according to Riccardo Perfetti, head of medical affairs at Sanofi's diabetes unit. He was quoted by Bloomberg as saying “I find it surprising that today after so many scientific reports on this topic, we’re still discussing these very small studies”.

He added that “patients using insulin may be compared to patients not using insulin, which might be a gigantic methodological mistake. People using insulin are usually much older and have been diabetic for many years.”

The US Food and Drug Administration began a review in July 2009 following the publication of four observational studies, three of which suggested an increased risk of cancer associated with the use of Lantus. However in January this year, the agency determined that the evidence presented in the studies is inconclusive, due to limitations in how the studies were designed and carried out.