Diabetes and cancer: 5 years into the recent controversy.

Diabetes and cancer are common chronic disorders. The literature has long recognised that type 2 diabetes (T2D) is associated with an increased incident risk of several cancer types, independent of the mutual risk factor, obesity. However, in June 2009, four papers were published simultaneously in Diabetologia, the official journal of the European Association for the Study of Diabetes, raising questions of a link between diabetes therapies, notably the long-acting insulin analogue, glargine, and increased cancer risk. These papers awakened an unprecedented debate in the diabetes community, drawing in cancer experts and bringing together representatives from these two large, traditionally non-intersecting, biomedical communities. This Current Perspective summarises the events that followed the 'breaking news' from summer 2009: the pitfalls encountered; the increased mutual understanding between diabetes and cancer researchers; and the direction of current research. Much of the debate on the clinical impact of this controversy has been played out in the diabetes literature: here, we update the oncology readership.