New study below [1].
"Using national Veterans Affairs databases, we identified all men diagnosed with PCa between 2000-2008 that were treated with ADT with follow-up through May of 2016. Exclusions included treatment with ADT for ≤6 months or ADT receipt concurrently with localized radiation."
"The cohort after exclusions consisted of 87,344 patients: 61% were no DM {diabetes mellitus}, 22% were DM no metformin, and 17% were DM on metformin."
i.e. there understandably was no arm for no-DM+Metformin. Non-diabetics who use Metformin should bear in mind that the results are for diabetics.
There was "improved survival in DM on metformin (HR 0.82 ...) vs. DM no metformin (HR 1.03 ...) with no DM as referent group."
For cancer-specific survival: "improved survival in DM on metformin (HR 0.70 ...) vs. DM no metformin (HR 0.93 ...) with no DM as referent group."
"Metformin use in Veterans with PCa receiving ADT is associated with improved oncologic outcomes."
-Patrick