Occupational Asbestos Exposure and Kidney Cancer: Systematic Review and Meta-analysis of Cohort Studies

Abstract

Objectives: An estimated 125 million workers are exposed to asbestos worldwide. Asbestos is classified by the International Agency for Research on Cancer as a Group 1 carcinogen. The association between occupational asbestos exposure and kidney cancer is not well established however. This study aimed to determine the mortality and incidence of kidney cancer in workers who have been exposed to asbestos. We performed a systematic review and meta-analysis to evaluate the association between occupational asbestos exposure and kidney cancer.

Methods: Medline, EMBASE, and Web of Science were searched according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines for articles on occupational asbestos exposure and kidney cancer. The studies reported the standardized mortality ratio (SMR) or standardized incidence ratio (SIR) of kidney cancer in workers exposed to asbestos. SMRs or SIRs with its 95% confidence interval (CI) were pooled using a fixed-effect model.

Results: Forty-nine cohort studies involving 335 492 workers were selected for analysis. These studies included 468 kidney cancer deaths and 160 incident cases. The overall pooled-SMR of kidney cancer was 0.95 (95% CI: 0.86-1.05), with no significant heterogeneity (PQ = 0.09, I2 = 24.87%). The overall pooled-SIR of kidney cancer was 0.95 (95% CI: 0.79-1.11), with no significant heterogeneity (PQ = 0.68, I2 = 0.00%). Subgroup analysis did not find any increased association with occupational asbestos exposure. There was no evidence of publication bias with Egger's test P values of 0.08 for mortality studies and 0.99 for incidence studies.

Conclusions: This systematic review and meta-analysis did not show evidence of association between occupational asbestos exposure and kidney cancer mortality or incidence.

Keywords: asbestos; kidney cancer; meta-analysis; occupational exposure; systematic review.

Figure 1.

PRISMA flow diagram of the meta-analysis.

Figure 2.

SMR estimates and 95% CIs of kidney cancer associated with occupational asbestos exposure. Weights are from fixed-effects analysis. Study-specific SMRs are shown as squares, with the horizontal lines representing the 95% CIs for the study-specific SMRs. The area of the squares represents weight of the individual study. The pooled-SMR is shown as a diamond. The middle of the diamond corresponds to the pooled-SMR, and the width of the diamond represents the 95% CI. The vertical dashed line provides a visual comparison of the pooled-SMR with the corresponding study-specific SMRs. I², I² statistic; P, P value for Cochran Q test; Q, Cochran Q test.

Figure 3.

SIR estimates and 95% CIs of kidney cancer associated with occupational asbestos exposure. Weights are from fixed-effects analysis. Study-specific SIRs are shown as squares, with the horizontal lines representing the 95% CIs for the study-specific SIRs. The area of the squares represents weight of the individual study. The pooled-SIR is shown as a diamond. The middle of the diamond corresponds to the pooled-SIR, and the width of the diamond represents the 95% CI. The vertical dashed line provides a visual comparison of the pooled-SIR with the corresponding study-specific SIRs. I², I² statistic; P, P value for Cochran Q test; Q, Cochran Q test.

Figure 4.

Begg’s funnel plot for evaluating publication bias showing the natural logarithm of kidney cancer SMR (LnSMR) plotted against the standard error of the LnSMR.

Figure 5.

Begg’s funnel plot for evaluating publication bias showing the natural logarithm of kidney cancer SIR (LnSIR) plotted against the standard error of the LnSIR.