14 April, 2017

It is well known that asbestos exposure significantly increases the risk of contracting mesothelioma – an aggressive type of lung cancer – but is there any evidence that it increases breast cancer risk?

Virgil Anderson of mesothelioma.net, a U.S. support group for mesothelioma sufferers, suggests there may be.

Breast cancer and mesothelioma may not initially seem to have much in common. One is most common in women, while the other is rare and most often seen in men. Researchers, however, have found significant similarities, from diagnostic markers (1) to symptoms and treatments (2) that slow the growth of tumours.

Breast cancer causes and risk factors

Breast cancer is a malignant cancer of breast tissues, and it can occur in men and women, although it is much more common in women. It is the most common cancer in women in the UK and the second most common cancer in American women, after skin cancer.

The exact cause of most breast cancer is unknown. Cells in the breast tissue begin to grow abnormally and divide more rapidly to form a tumour, but why this happens is not well understood. There are many well-defined risk factors for breast cancer, and some evidence suggests exposure to asbestos may be one of them.

Well-known risk factors for breast cancer include having certain genes identified as contributing to breast cancer. Others are being female and older, having a family history of breast cancer, being obese, never having been pregnant, being exposed to radiation, undergoing hormone therapy for menopause, and drinking alcohol (3).

Evidence asbestos exposure contributes to breast cancer

There is some evidence that asbestos could be a contributing cause of certain breast cancers, although studies have shown mixed results. One reason for this uncertainty may be the small number of women who have had occupational asbestos exposure.

An association between asbestos and breast cancer was indicated by a study that examined the mortality of asbestos factory workers in London, which found a slightly elevated incidence of breast cancer mortality in female asbestos factory workers (4). Earlier studies investigating the number and presence of asbestos fibres in lung tissue samples taken at a London hospital found an increased prevalence of asbestos in samples from women who had breast cancer (5). A more recent Finnish study found occupational asbestos exposure was associated with increased breast cancer risk, but only in post-menopausal women (6). However, in a 2009 Australian study, over 3,000 women from a town—home to an asbestos manufacturing company until 1966—were compared to the general population, and while ovarian and cervical cancer rates were slightly higher in those that lived near the factory, breast cancer rates were not (7).

How asbestos could contribute to breast cancer is not understood. It causes mesothelioma and lung cancer because the fibres are inhaled and lodged in the lungs (8). Asbestos fibres may move through the lymphatic fluid to the chest and breast tissue. Another hypothesis is that fibres pierce the lung and associated tissue and migrate into the chest wall (7).

How women may be exposed to asbestos today

All types of asbestos were banned in the UK in 1999, but any structure built or refurbished before then (especially between the 1950s and mid-1980s) may still have asbestos. Even if a house has older asbestos materials, this does not mean it poses a danger. It is only risky if it has deteriorated or gets damaged, exposing the fibres, which can become airborne. Possible sources of asbestos in older homes include insulation around heating systems, cement water tanks, ducts, plumbing, electrical wires, siding materials, and ceiling tiles.

School buildings are also a possible source of asbestos exposure because many were built before the ban was put in place. If any of the asbestos materials have been damaged, they could pose a risk.

Both breast cancer and mesothelioma are terrible diagnoses to receive. Treatment is challenging and may cause more side effects than the cancer itself. The interesting findings that these types of cancer may have similarities may mean that there is potential to develop better diagnostic techniques and treatments that may extend or even save the lives of patients struggling with these types of cancer.

Nowadays, women are exposed in many ways as men, including military exposure. Understanding occupational hazards is key to avoiding the inhalation of asbestos fibres.

Virgil Anderson

Virgil is a member of mesothelioma.net, a U.S. support group for mesothelioma sufferers. He would like to acknowledge this blog is a result of a team effort by members of mesothioma.net.

References

1. Panou, V. et al. (2015). The established and future biomarkers of malignant pleural mesothelioma. Cancer Treatment Reviews 41: 486-495.

2. Bonelli et al. (2017). New therapeutic strategies for malignant pleural mesothelioma. Biochemical Pharmacology 123: 8–18.

3. https://www.mayoclinic.org/diseases-conditions/breast-cancer/symptoms-causes/dxc-20207918

4. Berry, G. et al. (2000). Mortality of factory workers in east London 1933-80. Occupational and Environmental Medicine 57: 782-785.

5. Doniach, I. et al. (1975). Prevalence of asbestos bodies in a necropsy series in East London: association with disease, occupation, and domiciliary address. British Journal of Industrial Medicine 32(1):16-30.

6. Weiderpass, et al. (1999). Breast cancer and occupational exposures in women in Finland. American Journal of Industrial Medicine 36(1): 48-53.

7. Reid, A. et al. (2009). Gynecologic and breast cancers in women after exposure to blue asbestos at Wittenoom. Cancer Epidemiology Biomarkers and Prevention 18(1): 140-147.

8. Omura, Y. (2006). Asbestos as a possible major cause of malignant lung tumors (including small cell carcinoma, adenocarcinoma & mesothelioma), brain tumors (i.e. astrocytoma & glioblastoma multiforme), many other malignant tumors, intractable pain including fibromyalgia, & some cardio-vascular pathology: Safe & effective methods of reducing asbestos from normal & pathological areas. Acupuncture and Electro-therapeutics Research 31(1-2): 61-125.



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