More than 250,000 women and men in the US will be diagnosed with breast cancer this year. Most of those cases are random, that is very few cases run in families with known genetic risk factors, but occur sporadically over a lifetime influenced by many factors. The exact causes of breast cancer are not yet fully understood by scientists.
BCRF investigators at Columbia University in New York led a study looking at the intersection of genetic risk factors and environmental exposures, one of the first and largest studies of its kind. PAH (polycyclic aromatic hydrocarbons) are a group of environmental pollutants comprised of hundreds of different chemicals. They occur naturally in petroleum and coal products such as crude oil, gasoline and coal and are released in the atmosphere when coal, oil, gas, wood, garbage, or tobacco are burned. As a class, PAH represent the most prevalent of environmental pollutants. Humans are exposed to PAH through motor vehicle exhaust, cigarette smoke, wood smoke, fumes from asphalt roads, or by eating grilled or charred meats or foods contaminated by PAH during the food manufacturing process.
In the new study published in the British Journal of Cancer, BCRF investigators, Drs. Mary Beth Terry and Regina Santella measured markers of PAH exposure in the blood of healthy women enrolled in the New York Breast Cancer Registry Study and recorded the number of breast cancer cases over the course of 10 years. The investigators found that women with the highest risk of breast cancer according to a risk prediction model called BOADICEA (BOADICEA), had an increased risk of disease occurrence when exposed to PAH – more than two times the risk of similarly high-risk women with lower PAH exposure.
In the current study, the investigators prospectively measured the levels of PAH in the blood of a subset of healthy (cancer-free) participants and followed them over time to record the incidence in breast cancer. At the beginning of the study, they calculated 10-year breast cancer risk on all participants using a the BOADICEA risk assessment model. Eighty (80) women developed breast cancer and 156 remained cancer free during the study. PAH were detected in 64 percent of those diagnosed with breast cancer compared to 51 percent in those who did not, indicating a 2-fold increase due to the PAH exposure in this high-risk population.
The investigators also found that as breast cancer risk increased on the BOADICEA scale, so did the effect of exposure to increasing levels of PAH on breast cancer risk. The authors concluded this is an important study looking at the influence of both genetic and environmental factors and that further studies are needed to confirm the findings.
In a conversation with BCRF, Dr. Terry noted that “this is the first study to prospectively examine whether exposure to PAH, as measured through blood biomarkers, increases risk in women at high risk of breast cancer and demonstrates that environmental exposures may modify breast cancer risk even in those at highest risk of breast cancer. Our next steps are to repeat this study in a larger cohort.”
Read more about Drs. Terry and Santella’s BCRF research here.
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