Air pollution and survival in patients with malignant mesothelioma and asbestos-related lung cancer: a follow-up study of 1591 patients in South Korea

Our plain-English summary of Air pollution and survival in patients with malignant mesothelioma and asbestos-related lung cancer: a follow-up study of 1591 patients in South Korea, by D.A. Huh, Y.H. Choi, L. Kim, et al (Environmental Health, 2024).

The study

• Authors: D.A. Huh, Y.H. Choi, L. Kim, K. Park, J. Lee, S.H. Hwang, K.W. Moon, M.S. Kang, Y.J. Lee
• Journal: Environmental Health
• Published: 2024;23(1):56
• Cited by: 16 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Background: Despite significant advancements in treatments such as surgery, radiotherapy, and chemotherapy, the survival rate for patients with asbestos-related cancers remains low. Numerous studies have provided evidence suggesting that air pollution induces oxidative stress and inflammation, affecting acute respiratory diseases, lung cancer, and overall mortality. However, because of the high case fatality rate, there is limited knowledge regarding the effects of air pollution exposures on survival following a diagnosis of asbestos-related cancers. This study aimed to determine the effect of air pollution on the survival of patients with malignant mesothelioma and asbestos-related lung cancer.

Methods: We followed up with 593 patients with malignant mesothelioma and 998 patients with lung cancer identified as asbestos victims between 2009 and 2022. Data on five air pollutants-sulfur dioxide, carbon monoxide, nitrogen dioxide, fine particulate matter with a diameter < 10 μm, and fine particulate matter with a diameter < 2.5 μm-were obtained from nationwide atmospheric monitoring stations. Cox proportional hazard models were used to estimate the association of cumulative air pollutant exposure with patient mortality, while adjusting for potential confounders. Quantile-based g-computation was used to assess the combined effect of the air pollutant mixture on mortality.

Results: The 1-, 3-, and 5-year survival rates for both cancer types decreased with increasing exposure to all air pollutants. The estimated hazard ratios rose significantly with a 1-standard deviation increase in each pollutant exposure level. A quartile increase in the pollutant mixture was associated with a 1.99-fold increase in the risk of malignant mesothelioma-related mortality (95% confidence interval: 1.62, 2.44). For lung cancer, a quartile increase in the pollutant mixture triggered a 1.87-fold increase in the mortality risk (95% confidence interval: 1.53, 2.30).

Conclusion: These findings support the hypothesis that air pollution exposure after an asbestos-related cancer diagnosis can negatively affect patient survival.

© 2024. The Author(s).

In plain English

This follow-up study examined air pollution and survival among 593 patients with malignant mesothelioma and 998 with lung cancer recognized as asbestos victims in South Korea between 2009 and 2022. Exposure after diagnosis to sulfur dioxide, carbon monoxide, nitrogen dioxide, PM10 and PM2.5 came from local monitoring stations, or from regional stations when local data were missing or incomplete. Analyses were adjusted for age, sex, smoking, cell type, treatment and type of asbestos exposure. The authors reported that one-, three- and five-year survival rates fell with higher exposure. Their table showed exceptions, such as higher mesothelioma survival in the second than in the lowest PM2.5 quartile. After adjustment, higher exposure to each pollutant was associated with higher mortality. A quartile increase in the pollutant mixture was associated with a 1.99-fold increase in mortality risk for mesothelioma (95% CI 1.62 to 2.44) and a 1.87-fold increase for lung cancer (95% CI 1.53 to 2.30). The authors concluded that the findings support the hypothesis that air pollution after diagnosis can negatively affect survival. They noted that monitoring data may not reflect patients' actual exposure.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Follow-up (cohort) study of patients with asbestos-related cancers. Survival was analysed with Cox proportional hazard models, and the pollutant mixture with quantile-based g-computation.
• Who was studied: 593 patients with malignant mesothelioma and 998 patients with lung cancer in South Korea, recognized as asbestos victims between 2009 and 2022 and followed to December 31, 2022. The article does not specify the site of the mesothelioma (pleural or peritoneal).

Asbestos exposure was:

• environmental for 304 (51.3%) mesothelioma and 423 (42.4%) lung cancer patients;
• occupational for 214 (36.1%) and 150 (15.0%);
• both (co-exposure) for 75 (12.6%) and 425 (42.6%).
• Exposure: Ambient sulfur dioxide (SO2), carbon monoxide (CO), nitrogen dioxide (NO2), PM10 and PM2.5, assigned from the date of diagnosis to the last follow-up or death. Values came from a monitoring station in the patient's residential area. Stations in the broader administrative region were used when the town had no station or its data covered less than 75% of follow-up. Asbestos exposure (environmental, occupational or co-exposure) was an adjustment factor. Fiber types were not reported.
• Main results:
  • Median survival was 1.58 years for patients with malignant mesothelioma and 2.58 years for patients with lung cancer.
  • The authors stated that 1-, 3- and 5-year survival rates for both cancer types decreased with increasing exposure to all pollutants. Their Table 2 shows exceptions to a uniform decline. For example, among mesothelioma patients, the second PM2.5 quartile had higher 1-, 3- and 5-year survival (89.9%, 69.7%, 62.4%) than the lowest quartile (70.9%, 52.7%, 49.1%). The authors also found median survival inconsistent across the two cancer types.
  • After adjustment, hazard ratios for both all-cause and cancer-specific mortality rose significantly with a 1-standard-deviation increase in each pollutant, in both cancer groups.
  • Among mesothelioma patients, the largest hazard ratios for cancer-specific mortality per 1-SD increase were:
• SO2: 1.45 (95% CI 1.32, 1.60)
• PM10: 1.47 (95% CI 1.28, 1.68)
• PM2.5: 1.65 (95% CI 1.40, 1.95)
  • Among lung cancer patients, the largest hazard ratios for cancer-specific mortality per 1-SD increase were:
• PM10: 2.13 (95% CI 1.86, 2.44)
• PM2.5: 1.99 (95% CI 1.74, 2.28)
• SO2: 1.48 (95% CI 1.33, 1.66)
  • For mesothelioma patients, a quartile increase in the mixture of all five pollutants was associated with a 1.99-fold increase in mortality risk (95% CI 1.62, 2.44). The effect was driven mainly by SO2, followed by PM10 and PM2.5.
  • For lung cancer patients, a quartile increase in the pollutant mixture was associated with a 1.87-fold increase in mortality risk (95% CI 1.53, 2.30). The effect was driven mainly by PM10, followed by PM2.5 and SO2.
  • The association with NO2 became non-significant after adjusting for particulate matter.
  • The dose-response relationship between air pollution exposure and mortality resembled a J-shaped curve.
• The authors' conclusion: The authors concluded that the findings support the hypothesis that air pollution exposure after an asbestos-related cancer diagnosis can negatively affect patient survival.
• Limitations the authors state:
  • Monitoring-station data may not precisely reflect patients' actual exposure. Cancer patients likely spend more time indoors, and exposure could be misclassified if patients sought care elsewhere.
  • Patients' education and income levels were not considered, because most respondents refused to provide them. A supplementary analysis adjusted for regional averages did not significantly change the results.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Lung cancer, Mesothelioma.

Medical terms in this study, explained in our Lexicon: Malignant Mesothelioma, Lung Cancer, Chemotherapy, Oxidative Stress, Inflammation, Hazard Ratio, confidence interval.

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