Light-chain multiple myeloma in WTC-exposed firefighters more than double that of the general population

By Robyn Boyle, RPh, for MDLinx
Published July 5, 2018

Key Takeaways

A study published in JAMA Oncology reported that environmental exposure to the World Trade Center (WTC) disaster site is associated with myeloma precursor disease, and may be a risk factor for developing multiple myeloma at an earlier age—particularly the light-chain subtype.

There is an increased risk of multiple myeloma associated with exposure to known and suspected carcinogens, although cohort studies evaluating multiple myeloma and other malignant neoplasms of first responders, construction workers, and volunteers at the WTC site have yielded variable results.

A prior study found that IgH-secreting and light-chain secreting multiple myeloma are preceded by monoclonal gammopathy of undetermined significance (MGUS) and light-chain MGUS, which can be detected in blood.

Ola Landgren, MD, PhD, from Memorial Sloan Kettering Cancer Center in New York, NY, and colleagues set out to characterize WTC-exposed firefighters with a diagnosis of multiple myeloma, and to conduct a screening study for MGUS and light-chain MGUS. In addition, the investigators compared the prevalence to that of a male population in Minnesota and attempted to determine an association with exposure-response time.

The WTC Health Program provided comprehensive physical and mental health services to Fire Department of the City of New York (FDNY) firefighters exposed to the WTC (N=12,942). A total of 16 white male firefighters with a post-9/11 diagnosis of multiple myeloma were identified and included in the case series population.

The analysis was restricted to white men because the only comparable, available screening study that included MGUS and light-chain MGUS assays was conducted in Olmsted County, MN, which has a predominantly white population. The final study cohort included 781 white, male, WTC-exposed firefighters.

During routine monitoring exams, serum samples were collected every 12 to 18 months and analyzed for MGUS or light-chain MGUS.

Demographic data were obtained from the FDNY employee database. A self-administered health questionnaire categorized their level of WTC exposure based on initial arrival time and duration at the WTC site.

The median age at diagnosis was 57 years, which is about 12 years younger than average. The median time between 9/11 and diagnosis was 12.0 years.

The majority (68.5%) of firefighters arrived at the WTC site on the day of the attacks and spent a mean of 3.17 months working at the WTC site. The comparison group from Olmsted County was assumed to have no exposure to the WTC.

Among white men aged 50 to 79 years, the age-standardized prevalence rate (ASR) of overall MGUS among WTC-exposed FDNY firefighters was 1.8-fold significantly higher compared with the rate among those from Olmsted County (ASR: 7.63 and 4.34 per 100 persons, respectively).

Among the same population, the ASR with only light-chain MGUS was 3.08 and 0.98 per 100 persons in FDNY firefighters and men in the Olmsted County study, respectively. The relative risk (RR) of having light-chain MGUS was 3.1-fold significantly higher (RR: 3.13) when comparing firefighters with the Olmsted County population.

For the FDNY firefighters, the ASR with only MGUS was 4.55 per 100 persons, which was slightly—but not significantly—higher than the Olmsted County cohort (ASR: 3.36; RR: 1.35).

Overall MGUS was assessed by WTC arrival time and by duration at the WTC site; the ASRs were greater than in the reference population for all arrival times, although an exposure gradient was not found. In addition, there was no significant difference in ASR when duration of work at the WTC site was included in the analysis.

The proportion of participants with CD20-expressing plasma cells—characteristics associated with a poorer prognosis—was more than 3.5-fold higher than in populations from previous studies (71% vs ~20%).

Among WTC-exposed, white, male firefighters, the proportion of light-chain multiple myeloma was more than double that of the general population (50% vs ~20%). The screening study revealed a 2-fold significantly higher risk of myeloma precursor disease, particularly light-chain MGUS, which is the precursor of light-chain multiple myeloma. It also showed that WTC exposure may be a risk factor for the development of multiple myeloma and its precursor disease.

The authors acknowledge that the study had several limitations. The study was underpowered to detect an exposure-response gradient association between WTC exposure and MGUS. In addition, a truly random sample of the US population was not available, the comparison study included only white men, and uncontrolled confounding between the FDNY population and the Olmsted County population is possible.

“Our results show that environmental exposure due to the WTC attacks is associated with myeloma precursor disease (MGUS and light-chain MGUS) and may be a risk factor for the development of multiple myeloma at an earlier age, particularly the light-chain subtype,” concluded the authors.

To read more about this study, click here

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