Long-term exposures to PM2.5 components increase the breast cancer mortality in the region of Inner Mongolia, China: a retrospective study based on mixture cure model

Abstract

Background: This study aims to investigate the association between long-term exposure to PM2.5 components and the breast cancer-specific mortality for patients in Inner Mongolia Autonomous Region by adjusting the potential effect of a cured population. Methods: This study adopted a retrospective cohort design, included 17,230 female breast cancer patients in Inner Mongolia from 2012 to 2021, collected daily average concentration of air pollutants in Inner Mongolia, and death causes. Non-parametric hypothesis tests were used to test the significance of breast-cancer cure rate. Semiparametric mixture cure model was utilized to analyze the effects of PM2.5 components, e.g., black carbon (BC), ammonium (), nitrate (), organic matter (OM), sulfate (), on breast cancer mortality and cure probability of female breast cancer patients. Sensitivity analysis was conducted to examine robustness of the results after excluding severe patients. Nonlinear mixture cure models were used to investigate the dose-response relationship. Results: Non-parametric test on the 8-year cure rate of 93.6% is significant (P < 0.001). The odds ratios (ORs) for unite increment per interquartile range (IQR) in PM2.5, BC,,, OM, and are 1.244 (95% CI: 1.151, 1.343), 1.399 (95% CI: 1.263, 1.548), 1.545 (95% CI: 1.328, 1.796), 1.488 (95% CI: 1.280, 1.728), 1.466 (95% CI: 1.308, 1.644), And 1.404 (95% CI: 1.265, 1.557), respectively. The hazard ratios (HRs) for unit increment per interquartile range (IQR) in PM2.5, BC,,, OM, and are 1.152 (95% CI: 0.993, 1.337), 1.260 (95% CI: 1.025, 1.549), 1.483 (95% CI: 1.234, 1.782), 1.454 (95% CI: 1.191, 1.775), 1.333 (95% CI: 1.108, 1.603), And 1.271 (95% CI: 1.086, 1.489), respectively. Sensitivity analysis revealed that, after excluding severe patients, the associations between PM2.5 and breast cancer mortality become more significant. An overall positive dose-response relationship was observed between PM2.5 component concentrations and the HRs for breast cancer death in nonlinear mixture cure models. Conclusion: Long-term exposure to high-concentration PM2.5 components is significantly associated with the increased mortality risk and the uncured probability of female breast cancer patients in Inner Mongolia region.