ASPO Abstracts
Phthalate metabolites and postmenopausal breast cancer risk
Category: Molecular Epidemiology & Environment, Molecular Epidemiology & Environment
Conference Year: 2018
Abstract Body:
Background Mounting laboratory and animal model evidence supports the potentially carcinogenic effects of phthalates, chemicals used as plasticizers in a wide variety of consumer products (e.g. cosmetics, medications, vinyl flooring). Phthalate metabolites (PMs) are measurable in nearly 100% of the U.S. population, though levels vary widely, and also have been reported in human breast milk. However, prospective data on whether phthalates affect human breast cancer risk is lacking. Methods We conducted a nested case-control study within the Women’s Health Initiative (WHI) prospective cohort (N=419 invasive cases and 838 matched controls). Controls were matched 2:1 on age, enrollment date, follow-up time, and study group (WHI clinical trial or observational study). We measured a panel of thirteen PMs and creatinine in two or three urine samples per participant over 1 to 3 years. Multivariable conditional logistic regression analysis was used to estimate risk ratios and 95% confidence intervals (RR, 95% CI) for breast cancer risk associated with each PM, with incorporation of measurement error correction approaches to account for the moderate within-participant variability of PMs. Results Overall, we did not observe statistically significant associations between individual PMs and breast cancer risk in analyses adjusted for matching factors, creatinine, body mass index, smoking status, and race/ethnicity: e.g., mono-2-ethylhexyl phthalate (MEHP; p trend=0.31; e.g. RR 0.91, 95% CI 0.62-1.33), monoethyl phthalate (MEP; p trend=0.16; e.g. RR 0.80, 95% CI 0.55-1.16 for 4th quartile vs 1st quartile), monohydroxy-isobutyl phthalate (MHiBP; p trend=0.11; e.g. RR 0.78, 95% CI 0.51-1.18 for 4th quartile vs 1st quartile, and monobenzyl phthalate (MBzP; p trend=0.11; e.g.. RR 0.86, 95% CI 0.57-1.28 for 4th quartile vs 1st quartile). Conclusions These results indicate that urinary phthalate metabolite levels are not related to increased breast cancer risk. However, some phthalate metabolites may be associated with decreased risk, possibly through anti-estrogenic actions. Future analyses will explore grouping metabolites by parent phthalate and also will separately evaluate breast cancer risk by tumor estrogen receptor status and explore potential effect modification by
Keywords: breast cancer phthalates endocrine disruption