Particulate matter (PM) air pollution exposure has been associated with cancer incidence and mortality especially with lung cancer. The liver is another organ possibly affected by PM due to its role in detoxifying xenobiotics absorbed from PM. Various studies have investigated the mechanistic pathways between inhaled pollutants and liver damage, cancer incidence, and tumor progression. However, little is known about the effects of PM on liver cancer survival.

—Deng et al.

The USC team used 20,221 California Cancer Registry patients with hepatocellular carcinoma (HCC) diagnosed between 2000 and 2009 to examine the effect of exposure to ambient PM with diameter <2.5 µ (PM_2.5) on HCC survival.

The study is the first registry-based study to link individual-level estimates of air pollution exposures after liver cancer diagnosis to survival.

PM_2.5 exposure after diagnosis was statistically significantly associated with HCC survival. After adjustment for potential confounders, the all-cause mortality HR associated with a 1 standard deviation (5.0 mg/m₃) increase in PM2.5 was 1.18 (95% CI: 1.16–1.20); 1.31 (95% CI:1.26–1.35) for local stage, 1.19 (95% CI:1.14–1.23) for regional stage, and 1.05 (95% CI:1.01– 1.10) for distant stage. These associations were nonlinear, with substantially larger HRs at higher exposures. The associations between liver cancer-specific mortality and PM_2.5 were slightly attenuated compared to all-cause mortality, but with the same patterns.

—Deng et al.

Resources

• Deng, H., Eckel, S. P., Liu, L., Lurmann, F. W., Cockburn, M. G. and Gilliland, F. D. (2017) “Particulate matter air pollution and liver cancer survival” Int. J. Cancer. doi: 10.1002/ijc.30779