January 14, 2020
4 min read

Sept. 11 first responders face increased incidence of leukemia, other cancers

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Moshe Shapiro, MS
Moshe Shapiro

First responders who worked at the site of the World Trade Center after the Sept. 11 attacks demonstrated increased overall risk for cancer, with elevated incidence of leukemia reported for the first time, according to study results published in JNCI Cancer Spectrum.

Multivariate analyses showed no correlation between cancer and magnitude or type of exposure.

“[This study] reflects the importance of continued medical monitoring of World Trade Center responders,” Moshe Shapiro, MS, biostatistician at World Trade Center Health Program General Responder Data Center in the department of environmental medicine and public health at Icahn School of Medicine at Mount Sinai, told Healio. “This paper can also promote wider understanding among primary care physicians of the potential health impact among their World Trade Center -exposed patients, as well as the availability of treatment for World Trade Center-related conditions.”

A previous study of the General Responder Cohort, published in 2013, showed increased incidence of thyroid, prostate and soft tissue cancers, as well as hematologic malignancies, among World Trade Center rescue and recovery workers.

The current study by Shapiro and colleagues included an additional 5 years of follow-up, spanning the cohort’s inception in July 2002 — shortly after cleanup of the site concluded — through 2013.

Sept. 11 first responders were shown to have increased risk of several cancer types, including prostate, thyroid, and leukemia.
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The researchers analyzed cancer incidence among 28,729 members of the cohort using cancer registry data from New York, New Jersey, Pennsylvania, Connecticut, North Carolina and Florida.

Median age of the responders was 38 years on Sept. 11. Most (85.5%) were men and 47.4% were non-Hispanic white.

The most common occupations of responders included construction (20.8%) and protective services (49%). Slightly less than half (44.4%) were exposed to the dust cloud caused by the collapse of the towers.

Researchers calculated standardized incidence ratios of selected cancers using both unrestricted criterion — with cancer counts and person-years of observation starting after Sept. 11 — and restricted criterion, with case inclusion and follow-up starting 6 months after enrollment in the World Trade Center Health Program. This enabled the investigators to account for selection bias.

Results using the restriction criterion showed 1,072 cancers among 999 responders, with elevated incidence for all cancer sites combined (SIR = 1.09; 95% CI, 1.02-1.16), prostate cancer (SIR = 1.25; 95% CI, 1.11-1.4) and thyroid cancer (SIR = 2.19; 95% CI, 1.71-2.75).

Incidence of leukemia also appeared elevated (SIR = 1.41; 95% CI, 1.01-1.92), in contrast to the earlier study.


Researchers also observed incidence of esophageal cancer and brain cancer, as well as decreased incidence of lung cancer and colorectal cancer, but none of those associations reached statistical significance.

The age of the responder on Sept. 11 correlated with elevated cancer risk, which increased 1.09-fold with every 1-year increase. Current smokers also appeared at significantly greater risk for cancer than with never-smokers (HR = 1.29; 95% CI, 1.07-1.57).

Multivariate analyses showed no association between cancer incidence and any World Trade Center exposure index for all cancer sites combined nor prostate cancer.

“The main point we were addressing in the discussion was the presence of a dose response — in other words, greater dust exposure meant greater exposure to a range of carcinogens and/or those with the most days on site are assumed to have the greatest exposure to carcinogens,” Shapiro said. “However, these self-reported exposures may not fully capture the complexity of the exposure environment at the World Trade Center site. Future research will focus on better differentiating the various pathways of exposures on site.”– by John DeRosier

For more information:

Moshe Shapiro, MS, can be reached at moshe.shapiro@mssm.edu.

Disclosures: Shapiro reports no relevant financial disclosures. Please see the study for a list of all other authors’ relevant financial disclosures.