Assessing the Burden of Asbestos-related Lung Cancer: Evidence Synthesis from Case-Control and Cohort Studies

Background and Objective: Surveillance efforts to assess the health impact of asbestos have focused on mesothelioma and asbestosis because they are easily attributable. In this study we have used two methods to estimate the impact on lung cancer. Methods: We systematically reviewed cohort studies of asbestos-exposed workers to identify the ratio of excess lung cancers to mesotheliomas and used the mean of these ratios to extrapolate the number due to asbestos in the larger population. We also systematically reviewed lung cancer case-control studies to identify the population attributable risks (PARs) and used the mean PAR to estimate the proportion of all lung cancers due to asbestos. Results: Forty-seven cohorts from 44 published studies met our inclusion criteria. Overall, the geometric mean ratio of excess lung cancer cases to mesotheliomas was 2.8 and the arithmetic mean was 4.5, indicating a skewed distribution. Twenty-one case-control studies met our inclusion criteria. The geometric mean was 9% while the arithmetic mean was 12%. Using the geometric means, which are less sensitive to extreme values but exclude values less than one, and 2005 U.S. mortality data, we arrive at approximately 7,600 excess lung cancers based on the ratio method and 14,700 based on the AR method. Conclusion: These results highlight the high toll that asbestos continues to have decades after measures were taken to drastically reduce exposure. Although mesothelioma is often the focus of attention, it is important to recognize that lung cancer is the most common cancer caused by asbestos.