Finasteride is also known by the brand names Proscar and Propecia. It is a type of medicine called a 5- alpha reductase inhibitor which works by stopping testosterone (a sex hormone) turning into another hormone called dihydrotestosterone (DHT), which can cause your prostate to grow bigger. Finasteride stops DHT being produced which helps shrink your prostate. It is therefore used to treat men with an enlarged prostate (benign prostate enlargement). It can help ease symptoms such as frequent and urgent urination, difficulty completely emptying the bladder or starting urination. Some studies have suggested that it MAY shrink the prostate tumour, but this is not the main objective of the FINESSE study. 

In this study, finasteride is being used ‘off label’ which means the medicine is being used in a way that is different to that described in the licence.