Therefore, we conducted additional analysis using a ����new-user design���� that required patients who did not have a history of cancer to be free of any studied insulin use during the 6-month period preceding the start of insulin treatment and censored patients when they stopped using glargine insulin or intermediate/Abmole Company BAY-60-7550 long-acting HI or started using another study insulin . Despite this design allowed us to estimate the incidence of cancer following a new episode of insulin treatment, follow-up duration was substantially shorter as compared with analysis on exclusive users which led to imprecise risk estimates. A nested casecontrol design comparing cumulative exposure of insulin glargine and intermediate/long-acting HI between cancer cases and timematched control may analyze the data more efficiently. Despite no excess of overall cancer incidence, our study showed that insulin glargine might be associated with a higher chance of pancreatic cancer and prostate cancer diagnosis. Due to few number of cancer cases, we could not evaluate the potential dose and duration of insulin glargine use that increased the occurrence of these two cancers. The mechanisms leading to this positive association was uncertain, as pancreatic cancer cells were previously shown to respond similarly to insulin glargine and human insulin, and survival in insulin glargine-treated patients after treatment for pancreatic cancer was similar to those on human insulin . However, due to the possibility that insulin analogues may promote the growth of subclinical tumors in a relative short duration of exposure, this potential risk deserved attention and needed to be evaluated in further studies. Similar to prior reports, the duration of exposure to insulin glargine in the present study was less than what would be reasonably anticipated for CX-4945 citations establishing a causal relationship with carcinogenicity. Taken together, these observations suggest that the use of insulin glargine increases the rate of development and subsequent detection of preexisting undetectable malignancies rather than malignant cell transformation and new cancer formation. In contrast to a significantly increased risk of breast cancer associated with glargine use reported by the Swedish and the Scottish studies , our study did not find a relation with breast cancer. Our study has several limitations.