Abstract C050: Association between outdoor air pollution and breast cancer survival: The Multiethnic Cohort Study
Authors: Cheng Iona , Yang Juan , Tseng Chiuchen , Wu Jun , Conroy Shannon M , Shariff-Marco Salma , Gomez Scarlett Lin , Whittemore Alice , Stram Daniel O , Le Marchand Loic , Wilkens Lynne R , Ritz Beate , Wu Anna H 
Published: September 2020

Abstract
Background: There are now 3.1 million breast cancer (BC) survivors with 4.5 million survivors projected by 2030. This high and growing burden speaks to the need of identifying modifiable factors that influence BC survival. Particulate matter (PM) air pollutants have been associated with increased mortality for cardiovascular disease (CVD) and several cancers. However, few studies have examined the impact of air pollution on mortality among BC cases. Within the Multiethnic Cohort (MEC), we examined the association between outdoor air pollution and mortality among African American (AA), Latino (LA), Japanese American (JA), and White (WH) women diagnosed with BC. Methods: Kriging interpolation of air pollution data from air monitoring stations was used to estimate PM2.5, PM10, and nitrogen oxides (NOx, NO2) exposures for 3,089 BC cases in the MEC, residing largely in Los Angeles County, linked to residential histories from date of diagnosis to date of death or 12/31/2013. Cox proportional hazard models were used to examine the association between time-varying air pollutants and mortality, accounting for age at diagnosis, race/ethnicity, marital status, chemotherapy, hormone therapy, radiation, surgery, stage, grade, hormone receptor status, tumor size, body mass index, smoking, alcohol, age at first birth, diabetes, CVD, and neighborhood socioeconomic status. All-cause, BC, CVD, non-BC/non-CVD mortality outcomes were evaluated. Stratified analyses were conducted by race/ethnicity, hormone receptor status, and stage. Results: Among the 3,089 BC cases, there were 1,125 all-cause deaths (474 BC, 272 CVD, and 379 non-BC/non-CVD) with an average of 8.1 years of follow-up. PM2.5 (per 10μg/m3), PM10 (per 10μg/m3), NOx (per 50 ppb), and NO2 (per 20 ppb) were associated with risk of all-cause (hazard ratios (HRs) range=1.25-1.72; p’s&lt;0.004) and CVD mortality (HR range=1.62-3.93; p’s&lt;0.0005). For AA cases, PM2.5, PM10, and NOx were associated with risk of CVD mortality (HR range=1.69-3.81; p’s&lt;0.04). For WH cases, PM2.5, PM10, and NOx were associated with risk of all-cause mortality (HR range=1.48-3.06; p’s&lt;0.02). Risk patterns were similar for LA and JA cases although associations did not reach statistical significance. For hormone receptor positive BC, PM2.5 and NOx were associated with risk of all-cause and CVD mortality (HR range=1.59-2.92, p’s&lt;0.006). For hormone receptor negative BC, NOx was associated with risk of CVD mortality (p&lt;0.01). For localized BC, PM2.5 and NOx were associated with risk of all-cause, CVD, and non-BC/non-CVD mortality (p’s&lt;0.04). For advanced BC, PM2.5 and NOx were associated with CVD mortality (p’s&lt;0.005). Conclusion: These findings provide strong evidence that air pollution is associated with overall and CVD mortality among BC cases, although no effect was found on risk of death due to BC. Moreover, it is essential to maintain stringent clean air laws. Future confirmatory studies and better understanding of the mechanisms of action are needed.
Citation Format: Iona Cheng, Juan Yang, Chiuchen Tseng, Jun Wu, Shannon M Conroy, Salma Shariff-Marco, Scarlett Lin Gomez, Alice Whittemore, Daniel O Stram, Loic Le Marchand, Lynne R Wilkens, Beate Ritz, Anna H Wu. Association between outdoor air pollution and breast cancer survival: The Multiethnic Cohort Study [abstract]. In: Proceedings of the Twelfth AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2019 Sep 20-23; San Francisco, CA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2020;29(6 Suppl_2):Abstract nr C050.