Increased Risk of Gastric Cancer in Asbestos-Exposed Workers: A Retrospective Cohort Study Based on Taiwan Cancer Registry 1980-2015

Our plain-English summary of Increased Risk of Gastric Cancer in Asbestos-Exposed Workers: A Retrospective Cohort Study Based on Taiwan Cancer Registry 1980-2015, by Y.J. Fang, H.Y. Chuang, C.H. Pan, et al (International Journal of Environmental Research and Public Health, 2021).

The study

• Authors: Y.J. Fang, H.Y. Chuang, C.H. Pan, Y.Y. Chang, Y. Cheng, L.J. Lee, J.D. Wang
• Journal: International Journal of Environmental Research and Public Health
• Published: 2021;18(14)
• Cited by: 2 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Asbestos has been recognized as a human carcinogen associated with malignant mesothelioma, cancers of lung, larynx, and ovary. However, a putative association between gastric cancer and asbestos exposure remains controversial. In this study, we aimed to explore gastric cancer risk of workers potentially exposed to asbestos in Taiwan. The asbestos occupational cohort was established from 1950 to 2015 based on the Taiwan Labor Insurance Database, and Taiwan Environmental Protection Agency regulatory datasets, followed by the Taiwan Cancer Registry for the period 1980-2015. Standardized incidence ratios (SIRs) for cancer were computed for the whole cohort using reference rates of the general population, and also reference labor population. Compared with the general population, SIR of the asbestos occupational cohort for the gastric cancer increased both in males (1.05, 95% confidence interval (CI): 1.02-1.09) and females (1.10, 95% CI: 1.01-1.18). A total of 123 worksites were identified to have cases of malignant mesothelioma, where increased risk for gastric cancer was found with a relative risk of 1.76 (95% CI: 1.63-1.90). This 35-year retrospective cohort study of asbestos-exposed workers in Taiwan may provide support for an association between occupational exposure to asbestos and gastric cancer.

In plain English

This retrospective cohort study from Taiwan examined gastric (stomach) cancer among 1,043,319 workers ever employed in 631 asbestos-related factories between 1950 and 2015. The workers were identified from labor insurance and environmental regulatory records and linked to the Taiwan Cancer Registry for 1980 to 2015. The study did not identify fiber types or have measured asbestos levels for these workers. Compared with Taiwan's general population, gastric cancer was more common than expected in male workers (3,088 cases; standardized incidence ratio 1.05, 95% CI 1.02 to 1.09) and in female workers (677 cases; 1.10, 95% CI 1.01 to 1.18). The authors used worksites where diffuse mesothelioma had been diagnosed (123 sites) as a marker of definite exposure. Workers at those sites had a gastric cancer rate ratio of 1.76 (95% CI 1.63 to 1.90) compared with workers at sites without mesothelioma. The authors concluded that their findings may support an association and that further studies are needed to verify causality. They noted they had no fiber measurements and no data on smoking, alcohol, diet or Helicobacter pylori infection. Some numbers differ between the article's text and tables.

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: Retrospective cohort study using administrative records linked to a cancer registry, with standardized incidence ratios and estimated rate ratios
• Who was studied: 1,043,319 workers ever employed in 631 asbestos-related factories in Taiwan between 1 March 1950 and 31 December 2015, followed for cancer through the Taiwan Cancer Registry for 1980 to 2015
• Exposure: Employment in asbestos-related factories. Fiber types and airborne fiber levels were not available for this cohort. Worksites where diffuse malignant mesothelioma (of the pleura or peritoneum) was diagnosed were used as a proxy for definite asbestos exposure.
• Main results:
  • Compared with the general population of Taiwan, the standardized incidence ratio for gastric cancer was 1.05 (95% CI 1.02 to 1.09) in male workers (3,088 observed versus 2,928.78 expected) and 1.10 (95% CI 1.01 to 1.18) in female workers (677 observed versus 618.03 expected).
  • For the whole cohort compared with the general population, the standardized incidence ratio for gastric cancer was 1.06 (p = 0.01); Table 1 gives a 95% CI of 1.03 to 1.10.
  • 123 worksites had cases of diffuse malignant mesothelioma.
  • Workers at worksites with diffuse mesothelioma had an estimated rate ratio for gastric cancer of 1.76 (95% CI 1.63 to 1.90) compared with workers at worksites without diffuse mesothelioma.
  • Compared with the whole asbestos cohort, workers at worksites with diffuse mesothelioma had an estimated rate ratio of 1.14 (95% CI 1.09 to 1.19).
  • Comparing worksites with versus without diffuse mesothelioma, the estimated rate ratio was 1.54 (95% CI 1.41 to 1.67) for male workers and 2.17 (95% CI 1.83 to 2.58) for female workers.
  • The gastric cancer incidence rate was 2.08 per 10,000 person-years in industries with diffuse mesothelioma and 1.18 per 10,000 person-years in industries without it.
  • Using a worker population as the reference, the overall standardized incidence ratio for gastric cancer was 1.21 (95% CI 1.16 to 1.25) in male asbestos-exposed workers.
  • Using the reference female worker population, the overall standardized incidence ratio for gastric cancer was 1.16 (95% CI 1.08 to 1.25) in female asbestos-exposed workers.
  • Among male workers, the standardized incidence ratio was 1.26 (95% CI 1.19 to 1.32) for employment of 1 to 9 years and 1.29 (95% CI 1.19 to 1.40) for 10 to 19 years. For 20 years or more, Table 3 shows 1.07 (95% CI 0.93 to 1.22).
  • Among male workers, the highest standardized incidence ratio by latency was for less than 10 years (1.46, 95% CI 1.32 to 1.60). For a latency of 30 years or more, Table 3 shows 1.01 (95% CI 0.94 to 1.08).
• The authors' conclusion: The authors concluded that their findings may provide support for an association between occupational exposure to asbestos and gastric cancer, and that further studies are needed to verify causality.
• Limitations the authors state:
  • The authors had no data on airborne asbestos fiber levels, and exposure may have varied substantially within the cohort. A job-exposure matrix could not be applied.
  • Data on gastric cancer risk factors such as alcohol, smoking, Helicobacter pylori infection and diet were not available, so the authors could not control for these potential confounders.
  • First employment in a potentially exposed industry was taken as the start of employment and latency, which may overestimate their true length.

Topics

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

Medical terms in this study, explained in our Lexicon: Stomach Cancer, Cohort Study, Cancer Registry, Malignant Mesothelioma, Asbestos Exposure, Standardized Incidence Ratio (SIR), confidence interval, Relative Risk.

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