Women with bigger breasts DO have higher risk of breast cancer, finds genetic study
Link may be sex hormone oestrogen that can trigger the growth of mammary glands and tumoursStudy is the first to identify genetic variants linking breast size with cancer
16:18 GMT, 4 July 2012
Scientists said the link between breast size and cancer could be down to the sex hormone oestrogen that can trigger the growth of mammary glands and tumours
Women with larger breasts are more likely to develop breast cancer, say scientists.
A study of more than 16,000 women found those with a larger bra size were at greater risk of the disease.
The link could be down to the sex hormone oestrogen that can trigger the growth of mammary glands and tumours.
The researchers found seven genetic factors significantly associated with breast size – three of which are strongly correlated with mutations already linked to breast cancer.
Dr Nicholas Eriksson said: 'One of the variants is known to regulate the expression of the oestrogen receptor gene which plays a vital role in breast growth and in the majority of breast cancer cases.
'Another one of these mutations is located in a region of the genome that often shows abnormalities in people with a certain subtype of breast cancer.'
He used data from his California-based personal genetics company 23andMe to make the first concrete link between breast size and breast cancer risks.
His findings published online in BMC Medical Genetics are based on the participants answers to survey questions including bra cup size and bra band size and comparing them with genetic data on millions of mutations.
Dr Eriksson said: 'Social norms and preferences aside, it turns out that breast size matters – but not quite in the way you think.
'The paper shows genetic factors influence whether women have double As or double Ds.
'This might sound a bit frivolous at first but our research uncovered surprising connections between the genetics of breast size and the genetics of breast cancer.
'All of our data was self-reported by female 23andMe customers of European descent who have opted into research and filled out an online survey.
'We specifically asked about bra cup size as an approximation for breast size using a 10-point scale ranging from 'Smaller than AAA' to 'Larger than DDD.'
His team also took into account age and breast-related surgeries including augmentation or reduction.
Women can be scanned for breast cancer using a mammogram machine. Women aged 50 to 70, who are registered with a GP, are automatically invited for screening every three years
Dr Eriksson said: 'Most of the genetic factors we identified for breast size lie in regions of great importance for breast cancer.
'These findings show some of the same biological pathways underlie both normal breast growth and breast cancer.
'This isn't a huge surprise if you think of cancer as unrestrained growth. But the relationship between breast size and breast cancer is complicated.
'Some studies have found that larger breast size as a young woman is associated with a slight increase in breast cancer risk, but only in women who were lean at a young age.
'The genetic factors we found aren't enough to explain this association, but support the idea that breast size and breast cancer are related.'
The analysis also controlled for age, genetic ancestry, breast feeding status and pregnancy history.
While breast size is heritable the study is the first to identify genetic variants linked to differences.
Dr Eriksson said: 'These results provide insight into the genetic factors underlying normal breast development and show that some of these factors are shared with breast cancer.'
He added: 'While the topic of breast size raised a few eyebrows when we first put out the survey – some thought it was too personal or couldn't be serious science – this paper demonstrates important scientific insights can come from the most unlikely of places.
'Although the connections between these genetic factors – breast size and breast cancer aren't fully understood – our findings give clues to the function of some of these genes and regions that might be useful in combating breast cancer.'