Association between Biomarkers of Environmental Exposure and Increased Risk of Breast Cancer

Experimental research has clearly shown that many environmental exposures that cannot easily be studied in humans can damage cells and cause disease, including cancer. It is very difficult to reconstruct real-life exposures for a multifactoral disease like breast cancer, where the timing of exposure is uncertain and the ability to reconstruct a lifetime exposure assessment using biomarker analysis or Geographical Information System (GIS) mapping techniques are limited. Despite all of the epidemiological research that has been performed, the causes of regional ‘hot spots’ for breast cancer in the United States, are not well understood at this time. The use of case–control studies to elucidate geographic risks of breast cancer, as was done in the LIBCSP studies, raises the question of what are the appropriate controls. In an area of high risk, it is possible that cases might be the most sensitive or hypersusceptible individuals, whereas local, regional controls are those who are delayed in developing breast cancer. This idea is supported by a recent study of sisters that were discordant for breast cancer, which found that DNA repair capacity was lower in patients with breast cancer compared with their disease-free sisters. Women in the lowest quartile for DNA repair had nearly 3 times the risk of breast cancer compared with their individual sisters (2.99 CI = 1.45–6.17, P = .02)