Association between wildfire PM2.5 and genitourinary cancer survival in California.

Abstract

10567 Background: Aerosolized particulate matter (PM) 2.5 (i.e., particles ≤ 2.5 µm in diameter or fine particles), including those that emanate from wildfires, has been previously associated with cancer risk and survival. While prior studies have focused primarily on etiology, little is known about the effects of wildfire PM2.5 on cancer prognosis. We sought to explore the effects of wildfire PM2.5 on genitourinary (GU) cancer survival in the state of California where episodic wildfires are considered a component of its climate. Methods: Using the California Cancer Registry, we identified incident prostate (n=81,261), urothelial (n=26,689), and kidney (n=26,303) cancers diagnosed between 2017-2020. Daily PM2.5 was estimated over the same period. Random forests regression was used to fuse diverse datasets (official air quality monitoring, satellite observations, meteorological modeling, predictive smoke modeling, and low-cost sensor networks [PurpleAir]) and produce a consensus estimate of PM2.5 for each centroid of a 1-square kilometer grid across California. We used home address at the time of cancer diagnosis to map each cancer case to the nearest centroid, and averaged PM2.5 exposures over the 6 months preceding cancer diagnosis for each case. Cox-proportional hazards regression was used to quantify the hazard ratio (HR) for death from any cause following cancer diagnosis associated with PM2.5, adjusting for key covariates including age, sex, race/ethnicity, neighborhood socioeconomic status, comorbidity, smoking status, rural/urban residence, and stage at diagnosis. Results: In patients with prostate cancer, a 10 µg/m³ increase in PM2.5 concentration was associated with an 18% increased hazard of death (HR=1.18; 95% confidence interval (CI)= 1.02-1.36, p=0.023). When stratified by stage at diagnosis, the association of PM2.5 and survival was limited to stages I, II, and III (HR=1.39; CI= 1.11-1.74, p=0.005) versus stage IV (HR=1.06; CI= 0.87-1.27, p=0.566). For urothelial cancer, a 10 µg/m³ increase in PM2.5 concentration was associated with a non-statistically significant 11% increased hazard of death (HR=1.11; CI= 0.96-1.29, p=0.151), which did not differ by stage at diagnosis. Kidney cancer survival was not associated with PM2.5 (HR= 0.94; CI= 0.79-1.11, p= 0.44). Conclusions: These findings suggest that higher PM2.5 exposure could influence prostate and urothelial cancer prognosis, perhaps through alteration of physiological pathways relevant to cancer aggressiveness or impairing response to treatment, including cellular immune response, inflammation, angiogenesis, or cell-signaling pathways. Further studies should look into the mechanisms and design mitigating strategies in patients diagnosed with these high-risk cancers who have been exposed to wildfire PM2.5.