MELBOURNE: A breast cancer diagnosis is terrible news for women younger than 35.
However, new Australian research shows for the first time it also spells trouble for close male as well as female relatives, who are much more likely to develop other tumours.
Fathers and brothers of such women - who have not been previously thought to be in added danger - face a five-fold risk of developing prostate cancer, a three-fold risk of brain cancer and an eight-fold risk of lung cancer.
Women are already known to be at higher risk of breast cancer if a sister or daughter develops the disease early, but the new research shows this risk goes much wider, doubling their risk of ovarian cancer and, along with men, giving them a higher risk of brain and lung cancers and quadrupling their risk of urinary tract cancers.
The risk figures were calculated by researchers who studied 2200 relatives of 500 women in Australia, Canada and the US diagnosed with breast cancer before the age of 35.
Lead investigator John Hopper, the director of research at the University of Melbourne's Centre for Molecular, Environmental, Genetic and Analytic Epidemiology, said the results, published yesterday in the British Journal of Cancer, were surprising.
"No one's ever pointed to this concept before, but then no one's ever studied this at a group level," he said. "The implications are that there could be a new cancer genetic syndrome . . . it suggests there's something going on here that we haven't known before."
Breast cancer is known to run in families, and is linked to two main gene mutations, known as BRCA1 and BRCA2.
The study suggests presently unknown gene variants must be at work, because BRCA1 and BRCA2 account for only 10 per cent of cases of breast cancer diagnosed in women under 35.
Of the 504 women with early onset breast cancer analysed in the study, 41 were found to have a BRCA mutation. These women were excluded from the risk calculations, strongly indicating the presence of other genetic factors.
Professor Hopper said one in 40 breast cancers occurred in women younger than 35, accounting for just over 300 women in Australia each year.
"This (result) may explain early onset breast cancers, but it may also give insights into the causes of other cancers," he said.
Andrew Penman, the chief executive of the Cancer Council NSW, said the finding that male relatives of young breast cancer patients were at added risk was new and would open up new research avenues.
"The exciting thing is it does cast some very early light on a potential poorly understood area of carcinogenesis, or cancer development," Professor Penman said.
Professor Hopper said there was "nothing magic to be done at the moment" for family members of women under 35 with a breast cancer diagnosis, as screening of symptomless patients carried drawbacks.
Those alarmed by the findings could call the Cancer Council on 131120 to receive advice, he said.
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