Prostate cancer accounts for a quarter of cancers in men
A faulty gene closely associated with breast cancer is also responsible for a particularly dangerous form of prostate cancer, research has confirmed.
A University of Toronto team found prostate cancer patients carrying the BRCA2 gene lived on average for four years after diagnosis.
The average survival time for a man with prostate cancer is 12 years.
Experts said the British Journal of Cancer study emphasised the importance of early detection and treatment.
Each year around 35,000 new cases of prostate cancer are diagnosed in the UK, and around 10,000 men die from the disease
The latest study - based on 301 patients - examined two closely related faulty genes, BRCA1 and BRCA2, both of which greatly increase a woman's risk of breast cancer, and are linked to ovarian cancer.
Both genes cut average survival times in men with prostate cancer who carried them - for men carrying BRCA1 the average survival time was eight years after diagnosis.
BRCA2 has already been linked to deadly prostate cancer, with an Icelandic study recording an average survival time among prostate cancer patients carrying the gene of just 2.1 years.
The latest study appears to confirm that link.
Around one in 500 men carry the defective BRCA2 gene. They can be five times more likely than men in the general population to develop prostate cancer.
Lead researcher Dr Steven Narod 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."
Dr Lesley Walker, of the charity Cancer Research UK, said: "Although only a very small percentage of men with prostate cancer will carry a faulty BRCA2 gene, they're much more likely to die from the disease.
"It is important that more research is done in this area to ensure that this group is targeted effectively so cancer is picked up at an early stage and, more importantly, that they are given the most appropriate treatment.
"Men with a strong family history of prostate or breast cancer can visit their GP for advice."