I do believe there is a trial that fits this description. It is called PROfound. Locations are specified in the UK but for whatever reason are not recruiting yet.
https://clinicaltrials.gov/ct2/show/NCT03012321?term=olaparib&cond=Prostate+Cancer+Metastatic&rank=1
I think the original article Jonathan has posted may refer to a trial result which did give amazing results for those who received olaparib (a PARP inhibitor) treatment AND were proved to have Genetic mutations, particularly BRCA2 or ATM.
https://www.ncbi.nlm.nih.gov/pubmed/26510020
Sorry that is an awfully dry report, but the key takeaway for me is that of the 16 patients with gene mutations 88% had a positive response to olaparib.
Olaparib is frequently used in Ovarian Cancer currently, so I presume that ethics committees etc would be less of an issue?
Jonathan, I see that your Dad had PC. Do you have any close female relatives who have had cancers? Particularly Breast or Ovarian? or other close male relatives with PC? If so, this could indicate familial (germline) BRCA gene mutations. Whilst this may seem bad news, it could also open up a path to a whole new subset of treatment options.