http://www.iflscience.com/health-and-medicine/diabetes-drug-could-let-humans-live-until-120
Life Extension has long been promoting metformin, and they cite studies showing much lower cancer incidence, especially pancreatic cancers.
The drug seems to work by making cells more sensitive to insulin - meaning the pancreas isn't stressed to make more insulin to keep blood sugars under control.
There was some controversy when the drug first came, but I think they have the correct form to use now.
Anyway, you need a prescription for Metformin, so at present, you'll need elevated blood sugar to qualify. Maybe if this study completes, it will be available as a general "anti aging" prescription. And any doctor can prescribe an approved medication for other uses. No harm in asking your doctor for a metformin prescription.