Women whose father or brother has prostate cancer are more likely to develop breast cancer, research shows.
Scientists believe the illnesses are caused by the same faulty gene passed down through families.
An American study of 78,000 women found that those whose fathers, brothers or sons had prostate cancer were 14 per cent more at risk of breast cancer.
But women were 80 per cent more likely to get the illness if their father, brother or son had prostate cancer and their mother or sister had breast cancer.
The findings – published in the journal Cancer – are further evidence that some types of breast and prostate cancer are caused by the same inherited, faulty gene.
Although doctors have been aware the illnesses run in families for several years, this research shows the faulty gene may be more important than they previously thought.
Its lead author says doctors should routinely ask women whether prostate cancer runs in her family when establishing her risk of breast cancer.
Women considered high-risk are offered more frequent x-rays, genetic tests and in some cases, preventative drugs such as Tamoxifen.
Breast and prostate cancers are the most common forms of the illness in women and men respectively.
There are 50,500 new cases of breast cancer in the UK each year and just under 42,000 of prostate cancer.
Dr Jennifer Beebe-Dimmer, of the Barbara Ann Karmanos Cancer Institute and Wayne State University School of Medicine in Detroit, studied the records of 78,171 women over a 16-year-period.
Those with a first degree male relative – brother, father or son – were 14 per cent more likely to have developed the illness.
But women with a first degree male relative with prostate cancer and mother or sister with breast cancer were 78 per cent more at risk.
Those with a first degree male relative – brother, father or son – were 14 per cent more likely to have developed the illness
Dr Beebe-Dimmer said: 'The increase in breast cancer risk associated with having a positive family history of prostate cancer is modest; however, women with a family history of both breast and prostate cancer among first-degree relatives have an almost two-fold increase in risk of breast cancer.
'These findings are important in that they can be used to support an approach by clinicians to collect a complete family history of all cancers - particularly among first degree relatives - in order to assess patient risk for developing cancer
'Families with clustering of different tumors may be particularly important to study in order to discover new genetic mutations to explain this clustering.'
Dr Caitlin Barrand, Senior Policy Manager at Breakthrough Breast Cancer, said: 'Although we've known for some time that there are links between prostate cancer and breast cancer, this study suggests the link might be more important than we previously thought.
'If further research confirms the findings of this study this may further improve our ability to estimate an individual's risk of developing breast cancer, and offer personalised plans to help prevent the disease, or diagnose it early, when it can be more successfully treated.
'We'd recommend that women speak to their GP if they have any concerns about their family history of cancer, and advise that they should be prepared to talk about cancers on both the mother and father's side - the GP should ask about both.'
Read more: http://www.dailymail.co.uk/health/article-2985758/Prostate-cancer-raises-breast-risk-daughters-Women-s-risk-increases-14-father-brother-suffered-disease.html#ixzz3TztEUjrA
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