HealthDay News — Several types of cancer have occurred significantly more often among World Trade Center rescue and recovery workers following the Sept. 11, 2001 terrorist attack, results of a registry study show.
WTC workers had a 43% higher risk for prostate cancer, double the risk for thyroid cancer, and almost a three-fold higher risk for myeloma from 2007 to 2008 compared with the general population of the state of New York, Jiehui Li, MBBS, of the New York City Department of Health and Mental Hygiene in Long Island City, and colleagues reported in the Journal of the American Medical Association.
However, increased cancer risk was not observed in people living or working near the site who did not participate in recovery efforts, and proximity to the site and intensity of exposure did not appear to increase cancer risk, the researchers wrote.
They advised caution in interpreting the results given the mixed findings, relatively short follow-up period, and lack of data on medical screening and other risk factors.
“The etiological role of WTC exposures in these three cancers is unclear. Longer follow-up of rescue/recovery works and participants not involved in rescue/recovery is needed with attention to selected cancer sites and to examine risk for cancers with typically long latency periods,” the researchers added.
Only one previous study has looked at the risk for cancer among WTC responders. Among the 9,853 male New York City firefighters included in that study, there was a 19% excess cancer incidence for firefighters exposed to the WTC site compared with unexposed firefighters (Lancet 2011; 378: 898-905).
To further assess the link between exposure to the WTC site and cancer, Li and colleagues analyzed data from the WTC Health Registry, which contains health-related information about 55,778 people who enrolled in the registry during 2003 to 2004. Total participants include 21,850 rescue/recovery workers and 33,928 other individuals who were not involved in rescue/recovery activities.
The researchers focused on cancer diagnosed among registry participants from 2007 to 2008, and calculated site-specific cancer incidences for the population of New York during that time period. They identified 1,187 cancers, 439 of which occurred in WTC responders cancers and 748 of which occurred in other registry participants.
Overall, there was no statistical difference in cancer incidence among WTC responders and the general population of New York — 546.7 vs. 479.6 per 100,000 person-years. When they analyzed cancer cases diagnosed from 2003 to 2006 and cases diagnosed during 2007 and 2008, the researchers found no significant differences among the two groups for either period: standardized incidence ratios (SIRs) of 0.94 for the early period and 1.14 for the later period.
The researchers also analyzed differences in cancer incidence among the two cohorts at 23 specific sites and found significant increases among WTC responders for three:
- Prostate cancer: SIR 1.43 (95% CI: 1.11-1.82)
- Thyroid cancer: SIR 2.02 (95% CI: 1.22-3.73)
- Multiple myeloma: SIR 2.85 (95% CI: 1.1-5.88)
Registry information was also used to classify patients into high, intermediate and low exposure groups, and further analyses were performed to determine cancer incidence among responders and nonresponders in each group. Researchers found no statistically significant differences in cancer rates based on exposure.
Study limitations included the self-reported nature of WTC exposure, the potential for recall error and a lack of data on other cancer risk factors.