Mortality after the 9/11 terrorist attacks among world trade center health registry enrollees with cancer

Background: While several studies have reported the association between 9/11 exposure and cancer risk, cancer survival has not been well studied in the World Trade Center (WTC) exposed population. We examined associations of 9/11-related exposures with mortality in WTC Health Registry enrollees diagnosed with cancer before and after 9/11/2001.

Patients and methods: This is a longitudinal cohort study of 5061 enrollees with a first-ever primary invasive cancer diagnosis between 1995 and 2015 and followed through 2016. Based on the timing of first cancer diagnosis, pre-9/11 (n = 634) and post-9/11 (n = 4427) cancer groups were examined separately. 9/11-related exposures included witnessing traumatic events, injury on 9/11, and 9/11-related post-traumatic stress disorder (PTSD). Associations of exposures with all-cause mortality were examined using Cox proportional hazards regression. In the post-9/11 group, cancer-specific mortality was evaluated by enrollee group (WTC rescue/recovery workers vs. non-workers) using Fine and Gray's proportional sub-distribution hazard models, adjusting for baseline covariates, tumor characteristics, and treatment.

Results: In the pre-9/11 group, 9/11-related exposures were not associated with all-cause mortality. In the post-9/11 group, increased risk of all-cause mortality was associated with PTSD (adjusted HR = 1.35; 95% CI = 1.11-1.65), but not with injury or witnessing traumatic events. Cancer-specific mortality was not statistically significantly associated with 9/11-related exposures. In rescue/recovery workers, increased non-cancer mortality risk was associated with PTSD (aHR = 2.13, 95% CI = 1.13-4.00) and witnessing ≥3 traumatic events (aHR = 2.00, 95% CI = 1.13-3.55).

Conclusions: We did not observe associations between 9/11-related exposures and cancer-specific mortality. Similar to findings in the non-cancer WTC exposed population, PTSD was associated with increased risk of all-cause mortality in cancer patients.