Air Pollution and Breast Cancer: An Examination of Modification by Underlying Familial Breast Cancer Risk

Abstract

Background: An increased familial risk of breast cancer may be each pollutant dichotomized at the median and breast cancer due to both shared genetics and environment. Women with a breast with interaction terms to examine modification by BOADICEA cancer family history may have a higher prevalence of breast score. cancer–related gene variants and thus increased susceptibility to Results: NO2 was associated with a higher breast cancer risk environmental exposures. We evaluated whether air pollutant and among those with BOADICEA score >90th percentile (HR, 1.28; breast cancer associations varied by familial risk. 95% CI, 1.05–1.56) but not among those with BOADICEA score Methods: Sister Study participants living in the contiguous ≤90th percentile (HR, 0.98; 95% CI, 0.90–1.06; Pinteraction ¼ 0.01). In United States at enrollment (2003–2009; N ¼ 48,453), all of contrast to NO2, associations between PM2.5 and breast cancer did whom had at least one first-degree relative with breast cancer, not vary between individuals with BOADICEA score >90th per-were followed for breast cancer. Annual NO2 and PM2.5 concentile and ≤90th percentile (Pinteraction ¼ 0.26). centrations were estimated at the enrollment addresses. We Conclusions: Our results provide additional evidence that air predicted 1-year familial breast cancer risk using the Breast and pollution may be implicated in breast cancer, particularly among Ovarian Analysis of Disease Incidence and Carrier Estimation women with a higher familial risk. Algorithm (BOADICEA). Using Cox regression, we estimated Impact: Women at higher underlying breast cancer risk may HRs and 95% confidence intervals (CI) for associations between benefit more from interventions to reduce exposure to NO2