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Greater Breast Cancer Risk for Women Working and Living in Cities

26 November 2007

Women working or living in cities have denser breasts than their counterparts in the country, therefore increasing the risk of developing breast cancer, according to new research by the London Breast Institute at The Princess Grace Hospital. Those women with the densest breasts are nearly four times the risk of developing the disease.

Dr Nicholas Perry, director of the London Breast Institute, presented these research findings at the annual meeting of the Radiological Society of North America (RSNA) on Monday 27 November 2007 at 1500 hours GMT. He said: "We have found that women who live or work in the City and Central London are more likely to have denser, glandular breasts and that is known to produce nearly four times the risk of developing breast cancer than fatty breast tissue."

The research team compared its data with that of women in other areas and revealed that there is a gradient of breast density. Women living or working in most highly populated areas have most dense breast tissue and those in the most rural areas tend to have the least dense tissue. Those with the densest breasts of all, the research identifies, are those working in the Square mile, even though many live outside of central London.

Dr Perry says: "These results indicate, for the first time, that women living and working in an urban environment have a higher risk of density of breast tissue and this increases the risk of developing breast cancer. It is known that women from higher socio-economic groups have a higher risk of breast cancer and both pollution and stress have been linked with increased risk of breast cancer. The preponderance of these factors in urban environments may be reflected in the greater breast density of women living and working in the city."

Prof. Kefah Mokbel, consultant breast surgeon at the Princess Grace Hospital and St George’s Hospital in London is one of the study authors. He believes that air pollution related to traffic emissions may significantly contribute to the higher breast density and hence the higher breast cancer risk among women living in cities like London. Air pollution contains tiny particles (polycyclic aromatic hydrocarbons and phenol derivatives) that mimic female sex hormones (oestrogens) and can disrupt the normal hormonal functions. Inhalation of these particles allows them to enter the systemic circulation through the lungs, bypassing the detoxification process that is normally carried out by the liver.

Breast tissue in women may be fatty, glandular or a mix of both. Those with more glandular breasts show denser tissue on a mammogram and these women with the densest breast tissue are the most likely to develop breast cancer.

The more dense the tissue, the more difficult it is to identify abnormalities on traditional mammogram x-rays, making it essential to use digital mammography that reveals potential breast cancers at the earliest stages of development.

Dr Perry says: "Our analysis of digital mammograms of 972 women revealed that those living and working in London had significantly denser breasts that those living in the suburbs or in rural areas. This difference was most pronounced in women aged between 45-54 years old, where increased breast density was twice as likely among Londoners."

City dwelling women are known to be less likely to attend for routine breast screening than those living in more rural areas. "The bottom line is that more effort needs to be focused on ensuring that women, including those under 50, who live or work in built-up areas have best quality screening available. The sooner any cancer is identified, the better," says Perry.

The London Breast Institute at the Princess Grace Hospital provides digital mammography as a part of a complete range of services covering diagnostics, through to surgery and follow-up care.