Relative Incidence of Multiple Primary Cancers in Male World Trade Center Responders: A Comparison With SEER

BACKGROUND: World Trade Center (WTC) responders were exposed to carcinogens during rescue, recovery, and cleanup operations following September 11th, 2001. Although responders have elevated risk of various primary cancers, they may also have an increased risk of second primary cancers. This study evaluates the incidence of multiple primary cancers among male responders compared with a population-based cohort. METHODS: We assembled a cohort of male WTC general responders with cancer diagnosed between 2002-2022 and compared them with male cancer patients from Surveillance, Epidemiology, and End Results (SEER) diagnosed during the same period. Crude and age-standardized proportion ratios (PRs) were used to compare the occurrence of multiple primary cancers between cohorts. RESULTS: Among 4,815 WTC responders, we observed higher age-standardized proportion of multiple primary cancers than among 3,376,402 SEER patients (Proportion Ratio [PR] = 1.84; 95% confidence interval [CI]: 1.61-2.11). The proportion of multiple primary cancers was higher among younger WTC responders than SEER patients (20-44 years: PR = 3.76; 95% CI: 3.04-4.67; 45-54 years: PR = 1.36; 95% CI: 1.17-1.58), while responders aged 65+ had lower proportions (PR = 0.79; 95% CI: 0.65-0.96). CONCLUSIONS: Male WTC responders experience a higher burden of multiple primary cancers than the general U.S. population, particularly at younger ages, highlighting multiple primary cancers as an underrecognized consequence of WTC exposure. IMPACT: Enhanced cancer monitoring strategies may be warranted for WTC responders and other populations that have been similarly exposed.