Research by Dr Craig Currie of Cardiff University School of Medicine found metformin protects against cancer in people with type-2 diabetes, but insulin may increase cancer risk in a dose-dependent fashion.
He suggested that metformin could have a role in cancer prevention in people without diabetes.
People with type-2 diabetes on high insulin doses may benefit from screening and combination therapy with metformin.
Dr Jeffrey Johnson also presented data on cancer risk in people with type-2 diabetes. His research showed that the relationship between obesity, type-2 diabetes and cancer appears to be associated with insulin resistance and hyperinsulinemia.
He suggested glitazones may improve cancer outcomes.