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 . 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 . '
Scientists believe illnesses caused by same gene passed down families . Suggests doctors should ask women whether cancer runs in family . Comment: