Does finasteride cause breast cancer?

[alopie]

The other day I saw a warning on the national healthcare system in the UK, that some cases of male breast cancer have been reported and may be linked to finasteride.

There are two studies that link male breast cancer and finasteride:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5773955/ (significant increase in mbc cases)

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2956950/ (further investigation needed)

And there is also one other study performed by some Merck consultants that did not find any links (but those are consultants, so there is a conflict of interest).

My understanding is that the balance of oestrogen/testosterone may trigger malignancies, and this all makes sense from an endocrinological point of view. However, what is not clear is the amount of exposure needed (i.e. if it occurs at 5mg for 10 years, it is not fair to say that it will happen at 1mg for 10 years, but the risk might not be 1/5).

I know there are people here that take it for many years, and others that claim that male breast cancer can only coexist with gyno. So if you have gyno as a side effect, you stop and that's it.