The Swedish researchers studied the risk of cancer in over 50,000 brothers of men with prostate cancer. Thirty per cent of the men that had one brother only with prostate cancer were diagnosed with prostate cancer by age 75 years, about double the Swedish national average risk of 13 per cent. Their risk of aggressive prostate cancer was much lower: 9 per cent (national average risk 5 per cent).
In men that had both a father and a brother with prostate cancer, the risk of any form of prostate cancer was as high as 48 per cent; the risk of the aggressive form was 14 per cent.
The researchers also studied how the different risks were affected by the severity of the cancer in an affected brother or father:
“We expected that the risk of aggressive prostate cancer would not be much increased in brothers of men with the indolent form, but it turned out to almost as high as the risk among men with aggressive prostate cancer in the family,” says Associate Professor Ola Bratt at Lund University, who lead the research project. “This is an important finding that needs to be disseminated to the general public and to healthcare professionals. Men whose father or brother have an indolent, untreated prostate cancer are probably not aware that this increases their own risk of developing aggressive prostate cancer. They might not even know that there is prostate cancer in the family,” says Ola Bratt.