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Member Research & Reports

Member Research & Reports

UMass: Study Finds No Link Between Phthalates and Increased Breast Cancer Risk

In the largest study to date on phthalates and postmenopausal breast cancer, University of Massachusetts-Amherst School of Public Health and Health Sciences associate professor of epidemiology, Dr. Katherine Reeves found no association between breast cancer risk and exposure to phthalates.

Published in the Journal of the National Cancer Institute, the research “rules out any extreme increase in risk,” but still leaves open the question of whether some relationship exists between phthalate exposure and breast cancer.

“Our research has raised almost as many questions as it’s answered,” says Dr. Reeves, whose study was funded with a 3-year, $1.5 million National Institute of Environmental Health Sciences (NIEHS) grant. “I think this is an important contribution to the literature, but there’s still a lot more work to be done.”

For their prospective study, Dr. Reeves used data from the Women’s Health Initiative (WHI) involving more than 160,000 postmenopausal women. The researchers examined levels of 11 phthalate metabolites in urine samples from 419 women diagnosed with invasive breast cancer after Year 3 of the WHI. They also studied samples from 838 healthy women who didn’t develop breast cancer. Two or three urine samples from each participant – from baseline, Year 1 and Year 3 – were measured.

Dr. Reeves suggests examining 10 to 20 urine samples to allow researchers to more accurately characterize exposure levels. Future research would benefit from studying younger women.

“The most critical time for breast cancer development is in previous years. Looking at women in their 50s and 60s may not be the most important exposure period. We need to know the answer about whether or not these chemicals are causing breast cancer or other health outcomes. It’s a pressing issue and we’re trying to think of creative approaches to get not just an answer, but the right answer.”