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Scandinavian Journal of Work,... Dec 2005This study examined the association between silicosis and lung cancer in a systematic review (and meta-analysis) of the epidemiologic literature, with special reference... (Meta-Analysis)
Meta-Analysis
OBJECTIVES
This study examined the association between silicosis and lung cancer in a systematic review (and meta-analysis) of the epidemiologic literature, with special reference to the methodological quality of observational studies.
METHODS
We searched Medline, Toxline, BIOSIS and Embase (1966-May 2004) for original articles published in any language and systematically reviewed the bibliographies of the retrieved articles. Observational studies (cohort and case-control studies) were selected if they reported a measure of association [standardized mortality ratio (SMR), relative risk or odds ratio] relating lung cancer to silicosis.
RESULTS
Thirty-one studies (27 cohort studies, 4 case-control studies) met the inclusion criteria of the meta-analysis. Without any adjustment for smoking, the meta-analysis of the cohort studies indicated that the common SMR was 2.45 [95% confidence interval (95% CI) 1.63-3.66; homogeneity P<0.0001]. When the results of the cohorts for which mortality data were adjusted for smoking were pooled, the common SMR was 1.60 (95% CI 1.33-1.93; homogeneity P=0.52). In a "dose-response" analysis, the profusion of small and large opacities found in chest X-rays correlated with the risk of death from lung cancer. Overall, the case-control studies were more conservative in their conclusions.
CONCLUSIONS
Because of biases inherent to observational studies, it is likely that the risk of lung cancer among silicosis patients is overestimated in the current literature. There is nevertheless evidence, from data restricted to never-smokers and from a "dose-response" analysis, that silicosis and lung cancer are associated.
Topics: Bias; Dose-Response Relationship, Drug; Humans; Lung Neoplasms; Silicosis; Smoking
PubMed: 16425586
DOI: 10.5271/sjweh.949 -
Annals of Oncology : Official Journal... Jul 2006In 1997, a Monograph from the International Agency for Research on Cancer (IARC) classified occupational exposure to crystalline silica as carcinogenic to humans. Large... (Meta-Analysis)
Meta-Analysis Review
BACKGROUND
In 1997, a Monograph from the International Agency for Research on Cancer (IARC) classified occupational exposure to crystalline silica as carcinogenic to humans. Large amounts of epidemiological data have been published subsequently.
METHODS
We conducted a systematic review of epidemiological investigations on silica exposure and lung cancer risk published after the IARC Monograph, including 28 cohort, 15 case-control and two proportionate mortality ratio (PMR) studies. These were identified in the available literature.
RESULTS
The pooled RR of lung cancer, calculated using random effects models, from all cohort studies considering occupational exposure to silica was 1.34. The RRs were 1.69 in cohort studies of silicotics only, 1.25 in studies where silicosis status was undefined and 1.19 among non silicotic subjects. The pooled RR was 1.41 for all case-control studies. The RRs were 3.27 in case-control studies of silicotics only, 1.41 in studies where silicosis status was undefined and 0.97 among non silicotic subjects. The RR was 1.24 for PMR studies.
CONCLUSIONS
In this re-analysis, the association with lung cancer was consistent for silicotics, but the data were limited for non silicotic subjects and not easily explained for undefined silicosis status workers. This leaves open the issue of dose-risk relation and pathogenic mechanisms and supports the conclusion that the carcinogenic role of silica per se in absence of silicosis is still unclear.
Topics: Case-Control Studies; Cohort Studies; Humans; Lung Neoplasms; Occupational Exposure; Risk Assessment; Silicon Dioxide; Silicosis
PubMed: 16403810
DOI: 10.1093/annonc/mdj125