Dietary exposure to polychlorinated biphenyls and risk of breast, endometrial and ovarian cancer in a prospective cohort

BACKGROUND: Observational studies on polychlorinated biphenyl (PCB) exposure and hormone-related cancer risk are either inconsistent or lacking. We aimed to assess associations of dietary PCB exposure with breast, endometrial and ovarian cancer risk in middle-aged and elderly women. METHODS: We included 36 777 cancer-free women at baseline in 1997 from the prospective population-based Swedish Mammography Cohort. Validated estimates of dietary PCB exposure were obtained via a food frequency questionnaire. Incident cancer cases were ascertained through register linkage. RESULTS: During 14 years of follow-up, we ascertained 1593, 437 and 195 incident cases of breast, endometrial and ovarian cancer. We found no overall association between dietary PCB exposure and any of these cancer forms. The multivariable-adjusted relative risks comparing women in the highest and lowest tertile of PCB exposure were 0.96 (95% confidence interval (CI): 0.75, 1.24), 1.21 (95% CI: 0.73, 2.01) and 0.90 (95% CI: 0.45, 1.79) for breast, endometrial and ovarian cancer. In analyses stratified by factors influencing oestrogen exposure, possibly masking associations with PCBs, indications of higher risks were observed for endometrial cancer. CONCLUSIONS: This study suggests that dietary exposure to PCBs play no critical role in the development of breast, endometrial or ovarian cancer during middle-age and old ages.