New York City firefighters who were exposed to the World Trade Center (WTC) disaster in 2001 and to its subsequent clean-up may be at a greater risk for certain cancers than the general population, according to two new studies published online April 26 in JAMA Oncology.
However, Otis Brawley, MD, chief medical officer, American Cancer Society, says in an accompanying editorial that the findings are not authoritative at this time.
Nevertheless, he sympathizes with the impulse to seek certainty about a potential cause-and-effect relationship. “When these WTC heroes are diagnosed as having a cancer, even a cancer common in the population, there is a natural tendency to assume it is due to their service at the WTC,” Brawley writes.
In the first study, Ola Landgren, MD, from Memorial Sloan Kettering Cancer Center in New York City, and colleagues conclude that environmental exposure to the WTC disaster site is associated with myeloma precursor disease and “may be a risk factor” for the development of multiple myeloma at an earlier age, particularly the light-chain subtype.
The team searched medical registry records and found that 16 of the 12,942 WTC-exposed firefighters were diagnosed with multiple myeloma. The median age at diagnosis was 57 years, which is younger than the median age of 69 years for multiple myeloma diagnosis in the United States.
Fourteen of these 16 firefighters had protein isotype and free light-chain data available; 50% had light-chain multiple myeloma. This is much higher than the expected occurrence rate of 20% found in other studies, say the study authors. Both the authors and Brawley observe that some research suggests that light-chain multiple myeloma is more common in people with myeloma after chemical or inflammatory exposures.
The study authors also document that a cohort of 781 of the firefighters was 1.76 times more likely to have monoclonal gammopathy of undetermined significance (MGUS), which is a precursor to multiple myeloma, than a population of adults in Olmsted County, Minnesota (who were also screened for MGUS).
But these may be problems associated with firefighting in general, says Brawley. “One must appreciate that the firefighting profession is documented to be associated with a higher risk of MGUS and multiple myeloma compared with that of the general population,” he writes.
The study authors could have strengthened their argument by comparing the NYC firefighters “with an intensively screened age-matched cohort of firefighters from another big city” instead of the general residents of Olmstead County, says Brawley.
Ultimately, the 16 cases of multiple myeloma is a small proportion, says Brawley, and “it is difficult to make a firm correlation with WTC service.” However, the ACS medical director also declares that, over time, more cases of multiple myeloma may emerge and the link to WTC exposure may be “more apparent.”
In the second study, Ankura Singh, MPH, from the Albert Einstein College of Medicine, Bronx, New York, and colleagues generated projections for the expected excess of several cancers over the next 20 years among this same population of NYC firefighters with WTC exposure.
The authors used computer simulations to project cancer incidence for 14,474 WTC-exposed firefighters from 2012 to 2031. They predict that 2960 cancers will be diagnosed. However, they focus their study results on the 87.1% of the firefighters who are white men, for the sake of population uniformity; for these men, they project 2714 cancers vs 2596 cancers in a control population.
Among this subgroup, the authors expect more cancer of the prostate (1437 vs 863) and thyroid (73 vs 57) and more melanoma (201 vs 131). On the other hand, they expect fewer lung, kidney, and colorectal cancers among the firefighters.
Again, Brawley casts a skeptical eye on the findings. “Excess incidence and mortality for these cancers [prostate and thyroid cancers and melanoma] have been previously reported in firefighters from other cities,” he says.
He asks a blunt question: “Are the predicted increases [of the three cancers] due to WTC exposure or a career as a firefighter?”
The New York City firefighters “are to be respected for the difficult work they did,” says Brawley, but “there is a tendency to want to blame something for every diagnosed cancer.” At the moment, the correlations found in the two new studies do not mean causation, he concludes.
The multiple myeloma study was supported by the V Foundation for Cancer Research, the Byrne Fund, and other sources. The cancer incidence projection study was supported by the National Institute of Occupational Safety and Health. The authors of both studies and Brawley have disclosed no relevant financial relationships.
JAMA Oncol. Published online April 26, 2018. Landgren abstract, Singh abstract, Editorial
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