Insulin use is not significantly predictive for prostate cancer mortality in diabetic patients: a 12-year follow-up study

Study Type – Prognosis (inception cohort) Level of Evidence 2a What's known on the subject? and What does the study add? Even though a lower risk of prostate cancer has been reported in patients with diabetes, they may have a higher risk of cancer development involving the liver, pancreas, endometrium, colorectum, breast and bladder. Insulin may have mitogenic properties besides its metabolic function. However, whether exogenous insulin use for glycaemic control in diabetic patients could increase the risk of prostate cancer has rarely been studied. This is the first prospective follow‐up study for up to 12 years to show that exogenous insulin use for glycaemic control in the diabetic patients is not significantly predictive for prostate cancer mortality.

OBJECTIVE

• ? To evaluate whether insulin use in diabetic patients could be predictive for prostate cancer mortality.

PATIENTS AND METHODS

• ? A total of 39 135 diabetic men aged ≥40 years from a nationally representative cohort were followed prospectively from 1995 to 2006 for prostate cancer mortality.
• ? Cox proportional hazards models were used to estimate the hazard ratios for the following independent variables: age, diabetes type, diabetes duration, body mass index, smoking, insulin use and area of residence.
• ? The models were created for patients aged ≥40 years and ≥65 years, separately; and before and after excluding patients with a duration between onset of diabetes and prostate cancer mortality <5 years.

RESULTS

• ? A total of 105 diabetic men died of prostate cancer during follow‐up.
• ? Age was the only significant risk factor.
• ? Insulin use was associated with an insignificantly higher risk of prostate cancer mortality ranging from 24% to 49%.
• ? When stratified by the duration of insulin use <5 and ≥5 years, a lack of significant association was also observed.

CONCLUSIONS

• ? Insulin use in diabetic patients does not significantly predict the mortality from prostate cancer.
• ? Further confirmation in other ethnicities is needed.