Date Published: April 30, 2019
Publisher: Public Library of Science
Author(s): Laura A. McClure, Tulay Koru-Sengul, Monique N. Hernandez, Jill A. Mackinnon, Natasha Schaefer Solle, Alberto J. Caban-Martinez, David J. Lee, Erin Kobetz, Sreeram V. Ramagopalan.
Occupational exposures significantly contribute to the risk of adverse cancer outcomes, and firefighters face many carcinogenic exposures. Occupational research using cancer registry data, however, is limited by missing and inaccurate occupation-related fields. The objective of this study is to determine the frequency and predictors of missing and inaccurate occupation data for a cohort of career firefighters in a state cancer registry.
We conducted a linkage between data from the Florida Cancer Data System (1981–2014) and the Florida State Fire Marshal’s Office (1972–2012). The percentage and the odds of having a firefighting-related occupation code in the cancer record were calculated, adjusting for other occupation and cancer-related factors.
Among 3,928 career firefighters, nearly half (47%) were missing a registry-dervived occupation code and only 17% had a firefighting-related code. Males were more likely to have a firefighting-related code (OR = 2.31;95%CI: 1.41–3.76), as were those with more recent diagnoses (OR1992-2002 = 2.98;95%CI: 1.57–5.67; OR2003-2014 = 11.40;95%CI: 6.17–21.03), and those of younger ages (OR45-64y = 1.26;95%CI: 1.03–1.54; OR20-44y = 2.26;95%CI: 1.73–2.95).
Accurate occupation data is key for identifying increased risk of advserse cancer outcomes. Cancer registry occupation fields, however, are overwhelmingly missing for firefighters and are missing disproportionally by sociodemographic and diagnosis characteristics. This study highlights the lack of accurate occupation data available for hypothesis-driven cancer research. Cancer registry linkage with external occupational data sources represents an essential resource for conducting studies among at-risk populations such as firefighters.
Occupational exposures play an important role in the risk of cancer and cancer death. Indeed, it is estimated that occupational exposures contribute to 40,000 new cancer cases and 20,000 cancer deaths each year in the United States (US). A recent review suggests that 2–8% of all cancers may be attributable to occupational exposures. Firefighters, for example, face many hazardous and potentially carcinogenic exposures in their jobs[1, 4], and they have been shown to be at increased risk of many cancers[5–7]. Measuring the impact of occupational exposures, however, can be a challenge, particularly given the latency of cancer development.
The Florida Cancer Data System (FCDS) is the legislatively mandated, population-based cancer registry for the state of Florida in operation under the Florida Department of Health as part of NPCR. It has collected all newly diagnosed cancer cases in Florida since 1981. The Florida State Fire Marshal’s Office has collected firefighter certification records for all firefighters in the state since 1972 when certification was mandated.
Of the 3,928 firefighters with cancer in our enriched linked dataset, almost half were missing an occupation code of any kind (n = 1,848, 47.0%) in the cancer registry record for their first primary cancer (Table 1). Only 679 (17.3%) had a firefighting-related occupation code; of these, 79.2% (n = 538) were listed as firefighters, 9.9% (n = 67) were emergency medical technicians and paramedics, 7.8% (n = 53) were first-line supervisors of firefighting and prevention workers, and 3.1% (n = 21) were fire inspectors. The remainder of linked cases (n = 1,401, 35.7%) had an occupation code other than firefighting, which included 1,071 (27.3% of total sample) listed as “unemployed” or “retired” and 330 (8.4%) with any other occupation.
This study confirmed the overwhelming lack of accurate data in the occupation field of cancer registry records. While the linked firefighter cancer cases had a greater proportion of any occupation code present than in the FCDS dataset overall (53% vs. 30%), at only half of the study population, this represent a very poor source of data for occupational research. The greater proportion of codes present for our linked cases may be an example of reporting bias among occupations for which there is a known risk of cancer, as has been shown previously.