Combining Three Cohorts of World Trade Center Rescue/Recovery Workers for Assessing Cancer Incidence and Mortality

Abstract

Three cohorts including the Fire Department of the City of New York (FDNY), the World Trade Center Health Registry (WTCHR), and the General Responder Cohort (GRC), each funded by the World Trade Center Health Program have reported associations between WTC-exposures and cancer. Results have generally been consistent with effect estimates for excess incidence for all cancers ranging from 6 to 14% above background rates. Pooling would increase sample size and de-duplicate cases between the cohorts. However, pooling required time consuming steps: obtaining Institutional Review Board (IRB) approvals and legal agreements from entities involved; establishing an honest broker for managing the data; de-duplicating the pooled cohort files; applying to State Cancer Registries (SCRs) for matched cancer cases; and finalizing analysis data files. Obtaining SCR data use agreements ranged from 6.5 to 114.5 weeks with six states requiring >20 weeks. Records from FDNY (n = 16,221), WTCHR (n = 29,372), and GRC (n = 33,427) were combined de-duplicated resulting in 69,102 unique individuals. Overall, 7894 cancer tumors were matched to the pooled cohort, increasing the number cancers by as much as 58% compared to previous analyses. Pooling resulted in a coherent resource for future research for studies on rare cancers and mortality, with more representative of occupations and WTC- exposure.

Impact of healthcare services on thyroid cancer incidence among World Trade Center‐exposed rescue and recovery workers

“…Rescue/recovery workers include cleanup workers, construction and communication workers, EMS, firefighters, law enforcement, and volunteers. To ensure accurate case ascertainment and person‐time calculations, the New York State Cancer Registry (NYSCR) resolved duplicates and discordant dates of enrollment, diagnosis, and death 26 . Additional details regarding the creation of the Combined Cohort, including de‐duplication of subjects and data harmonization, are described elsewhere 26 …”

“…The Icahn School of Medicine at Mount Sinai and Stony Brook University IRB ruled the research exempt. Depending on the source cohort, participants provided informed consent, or their consent was waived 26 …”

“…Tumor characteristics such as diagnosis date, histology, and stage were also provided by state cancer registries. Cancer cases obtained from multiple states registries for the same participant were reconciled and de‐duplicated by the NYSCR 26 . Histological codes were categorized as defined by Davies and Welch 13 …”

Post‐9/11 excess risk of thyroid cancer: Surveillance or exposure?

“…Increased thyroid cancer risk was also found in the Fire Department of New York (FDNY) and the exposed population of the WTC Health Registry cohort confirming an excess risk with around twofold increase in thyroid cancer incidence rates in WTC‐dust exposed populations 3,4 . (Table 1) It has to be noted that recent efforts to pool the three individual cohorts resulted in a de‐duplicated cohort of 69,102 unique individuals with 7894 matched cancers, eliminating potential bias due to duplicate cancer cases 5 …”

“…These populations exposed to smoke and dust containing multiple pollutants released following the WTC disaster provide a unique opportunity to study the effect of various environmental exposures on the thyroid. Moreover, available exposure information has been reorganized in the recent effort to combine the different cohorts providing summary exposure data in a pooled data file 5 . To date, exposure to WTC dust has already been associated with inflammatory and immune responses in the tissue of WTC prostate cancer cases, displaying a distinct gene expression pattern resulting from exposure to the dust 24 .…”