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Does radon cause breast cancer?

Naturally-occurring radon can be found at higher than recommended levels in some people’s homes. A recent US study examined a potential link between radon exposure and breast cancer to help shed light on the question – does radon cause breast cancer?

Breast cancer is the leading cause of cancer-related death among women worldwide. There are different types of breast tumors according to their responsiveness to various hormones and the expression of proteins. Most breast cancers are estrogen-receptor (ER) positive and grow in response to the hormone estrogen. About two-thirds of these are also progesterone-receptor (PR) positive. In about a fifth of breast cancers, the cells make too much of a protein known as HER2. Between 10-20% of breast cancers are “triple-negative”, which means there are no estrogen and progesterone receptors and no expression of the HER2 protein. Some geographic variations of breast cancer incidence suggest that environmental factors may also play a role in its development.

High levels of naturally-occurring radon found in some homes

Radon is a naturally-occurring radioactive gas found in air, soil, rocks, and water.  The main source of indoor radon is from soil gas entering homes through foundation cracks.

Approximately 6% of US homes have radon levels above the Environmental Protection Agency recommended levels. Radon decay products enter the human body mostly by inhalation and deliver radiation doses to various organs including the breast. This could cause DNA damage.

Although this is a mechanism by which radon exposure could bring about changes that cause breast cancer, there have been few studies assessing whether the two are linked. Researchers conducted a study to look at the association between environmental radon exposure and breast cancer incidence in US women.

They recently published the results in the journal Environmental Health.

Assessing associations between radon exposure and breast cancer

The Nurses’ Health Study II (NHSII) is an ongoing study of over 116,000 US female registered nurses who were aged between 25 and 42 years at the start of the study in 1989. Participants reside in all 50 states. They completed questionnaires every two years giving information about any illness, medical history, diet, lifestyle factors, and health behaviors.

The researchers examined data from this questionnaire to identify participants who reported breast cancer. In these cases, their medical records were reviewed to confirm breast cancer and find out more about the type of tumor. The researchers also reviewed the residential addresses of the participants and used a National Laboratory computer model to calculate each participant’s overall radon exposure.

Environmental radon exposure not associated with overall risk of breast cancer

During the period of the study, almost 4,000 invasive breast cancers occurred. Careful statistical analysis showed that environmental radon exposure was not associated with invasive breast cancer risk overall. Looking in more detail at the various tumor types, radon exposure was also not associated with ER-positive or ER/PR-positive breast tumors.

However, there was a suggestive association between higher levels of radon exposure and risk of ER-negative, ER/PR-negative, and triple-negative tumors. Triple-negative tumor types are usually found in patients who have a gene mutation that prevents the repair of damaged DNA (BRCA1). The researchers suggest that radon exposure may be involved in similar DNA damage mechanisms.

Possible association with hormone receptor-negative breast tumors

This is the first study of its kind looking at environmental radon exposure and incidence of invasive breast cancer. Although there was no association found between radon exposure and risk of overall or hormone-receptor-positive breast tumors, there was a suggestive association with the risk of hormone-receptor-negative breast tumors.

Further research is needed to clarify this possible association.

Written by: Julie McShane, Medical Writer 

Reference: VoPham T, DuPre N, Tamimi RM, et al. Environmental radon exposure and breast cancer risk in the Nurses’ Health Study II. Environmental Health (2017) 16:97. DOI 10.1186/s12940-017-0305-6.

Julie Mcshane MA MB BS
Julie Mcshane MA MB BS
Julie studied medicine at the Universities of Cambridge and London, UK. Whilst in medical practice, she developed an interest in medical writing and moved to a career in medical communications. She worked with companies in London and Hong Kong on a wide variety of medical education projects. Originally from Ireland, Julie is now based in Dublin, where she is a freelance medical writer. She enjoys contributing to the Medical News Bulletin to help provide a source of accurate and clear information about the latest developments in medical research.


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