A 20-year follow-up study showed that high exposure to the plasticizer di-(2-ethylhexyl) phthalate (DEHP), metabolic susceptibility and early menarche can increase breast cancer risk by up to seven times among women, Academia Sinica said yesterday.
The large-scale longitudinal cohort study was led by academician and former vice president Chen Chien-jen (陳建仁), a distinguished research fellow at Academia Sinica’s Genomics Research Center, and a research team composed of members from the National Health Research Institutes (NHRI) and several local universities.
The results of the 20-year study were published last month in the Proceedings of the National Academy of Sciences of the US, one of the world’s most-cited and comprehensive multidisciplinary scientific journals.
Photo courtesy of Academia Sinica
Breast cancer has long been the most common type of cancer among women in Taiwan and many developed countries, with the trend also rising among younger women, but previous studies on the chronological link between DEHP exposure and breast cancer onset are not clear, the institution said.
The nested case-control study recruited 11,923 women in Taiwan in 1991 and 1992, and followed them through 2010, establishing a causal timeline that confirmed DEHP exposure preceded the development of breast cancer, they said.
Academia Sinica cited Chen as saying that the study collected urine samples from participants at the beginning, while keeping track of their lifestyle habits and environmental exposure for 20 years.
By linking their data with the national cancer registry data, the research team identified people from the group who were later diagnosed with breast cancer, and selected a matched control group of cancer-free women, he said.
Urine samples from 119 invasive breast cancer cases and 245 matched controls were retrieved from the frozen biospecimen bank to analyze DEHP metabolites, and the results indicated that people with higher urinary concentrations of DEHP metabolites have significantly increased risk of developing breast cancer during the follow-up period, Chen was cited as saying.
Academia Sinica quoted Chen Hui-chi (陳慧祺), the first author of the paper and former postdoctoral fellow at Academia Sinica’s Genomics Research Center, as saying that one of the study’s most significant breakthroughs is finding metabolic susceptibility (MEHP%) as a new and better biomarker reflecting a person’s ability to metabolize DEHP.
After DEHP enters the body, it is first metabolized into a more toxic primary metabolite, which is later converted into less toxic secondary metabolites, she said.
A higher residual percentage of primary metabolites in the body indicates that the person has a lower metabolic efficiency for the substance, she added.
Women with high MEHP% and high exposure to DEHP are 2.68 times more likely to develop breast cancer, she said.
When combined with the risk factor of early onset of menstruation (under 14 years old), the risk of developing breast cancer rises to 7.52 times, she said.
MEHP% reflects a person’s physiological capacity to metabolize DEHP, and the differences among individuals may be due to variations in innate biological constitutions, lifestyles, dietary choices and environments, making some women more susceptible to breast cancer even with the same level of DEHP exposure, she said.
Local and international studies have not yet recognized the importance of MEHP%, so this discovery offers a new entry point for future breast cancer risk assessment, she added.
Chen Chien-jen said DEHP is an endocrine disruptor widely used in plastic products, and the study serves as a reminder for high-risk groups to reduce their exposure to plasticizers, while emphasizing the importance of breast cancer screening.
The institution also cited Academia Sinica President James Liao (廖俊智) as saying the study explicitly showed that DEHP is a significant environmental carcinogen for breast cancer, providing a crucial scientific basis for future prevention strategies and risk assessments.
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