These findings could help tailor treatment and target chemotherapy more effectively to men with prostate cancer that is caused by a BRCA gene fault.
Carriers of the BRCA2 gene were found to live for an average of four years following a diagnosis of the disease, compared to an average of eight years in men carrying the BRCA1 gene.
Lead researcher, Dr Steven Narod, based at the University of Toronto in Canada, said: "We know that carrying a faulty BRCA2 gene increases a man's risk of getting prostate cancer, and our study shows that it also affects how long he will survive a diagnosis of the disease.
"This information is important because it shows that men with BRCA2 are not responding as well to current therapies, so we hope these findings could help doctors more effectively tailor treatment to this group."
Prostate cancer is the most common cancer in men in the UK. Around 35,000 new cases of the disease are diagnosed in the UK and around 10,000 men die from the disease each year. Around one in every 500 men carry the BRCA2 gene.