Comparing cancer risk estimates using occupational record linkage approaches in male Florida firefighters

Abstract

Background: Firefighters have an increased risk of cancer, but variations in reported results could be due to differences in occupational case ascertainment. This study compares cancer risk estimates generated by identifying firefighters from their occupational title available in the Florida Cancer Data System (FCDS) versus identification by a linkage method between the FCDS and the Florida State Fire Marshal's Office. Methods: Florida firefighter employment records (1972–2012; n = 109,009) were linked with FCDS data (1981–2014; ~3.3 million records), identifying 3760 primary cancers in male firefighters. Using the FCDS occupational data field we identified 1831 male cancer cases in those classified as firefighters, first-line supervisors of firefighting and prevention workers, fire inspectors, emergency medical technicians, or paramedics. Age and calendar year-adjusted odds ratios (aOR) and 95% confidence intervals for firefighters versus non-firefighters were calculated for both groups. Results: For skin cancers the risk estimate for FCDS-indentified firefighters was substantially lower than in the employment-record-linked firefighters (aOR = 1.06; 0.87–1.29 vs. 1.54; 1.37–1.73), but for endocrine system cancers it was greater (aOR = 2.36; 1.77–3.14 vs. 2.08; 1.71–2.53). Remaining cancer risk estimates were in the same direction for the two samples except for lymphoma (aOR = 1.10; 0.90–1.34 vs. 0.86; 0.75–0.99). Conclusion: Reliance on occupational title in cancer registry records to characterize firefighter cancer risk may result in estimates that are over- or underestimated depending on cancer site. The authors recommend moving toward national linkages between cancer registries and certification or other administrative records, which are a vital resource for firefighter cancer research.