Certified causes of death in patients with mesothelioma in South East England

Background: Mesothelioma is a highly fatal cancer that is caused by exposure to asbestos fibres. In many populations, the occurrence of mesothelioma is monitored with the use of mortality data from death certification. We examine certified causes of death of patients who have been diagnosed with mesothelioma, and assess the validity of death certification data as a proxy for mesothelioma incidence. Methods: We extracted mesothelioma registrations in the South East of England area between 2000 and 2004 from the Thames Cancer Registry database. We retained for analysis 2200 patients who had died at the time of analysis, after having excluded seven dead cases where the causes of death were not known to the cancer registry. The 2200 deaths were classified hierarchically to identify (1) mesothelioma deaths, (2) deaths certified as lung cancer deaths or (3) deaths from unspecified cancer, and (4) deaths from other causes. Results: 87% of the patients had mesothelioma mentioned on the death certificate. 6% had no mention of mesothelioma but included lung cancer as a cause of death. Another 6% had no mention of mesothelioma or lung cancer, but included an unspecified cancer as a cause of death. Lastly, 2% had other causes of death specified on the death certificate. Conclusion: This analysis suggests that official mortality data may underestimate the true occurrence of mesothelioma by around 10%.