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Asbestos exposure and laryngeal cancer.

Dear Dr, Sataloff:

I read with interest your editorial in the October issue, "Asbestos exposure and laryngeal cancer: Is there an association?" (1) I completely agree with the central point, that the simple association of two events does not prove that the first event causes the second. This point is important to understanding epidemiologic studies suggesting disease associations and highlights the timelessness of considering all of Koch's postulates and Hill's criteria of disease causality.

As to the specific question the authors raise regarding whether asbestos is a cause of laryngeal cancer, I share a concern that associations at a population/group level may be interpreted as proof that an individual's cancer has a specific cause. However, a critical monograph on the subject from the National Academies of Sciences was not referenced or reviewed. (2) This monograph represents the review and conclusions of an Institute of Medicine multidisciplinary committee of 12 distinguished members, backed by research staff as well as a separate and independent 12-person review committee. Neither I nor a member of my institution was a member of these committees.

The conclusion of the committee regarding laryngeal cancer was that despite "... the lack of confirmatory evidence from animal studies or documentation of fiber deposition in the larynx ... evidence is sufficient to infer a causal relationship between asbestos exposure and laryngeal cancer." In making this conclusion, the committee considered 35 cohort populations and 18 case-control studies. This work is a comprehensive review of this literature and a summary of the principal epidemiologic criteria supporting asbestos as a cause of laryngeal cancer, namely: (1) consistency of the epidemiologic studies, (2) biologic plausibility, (3) strength of association, (4) dose-response effect, and (5) effect modification.

We would hope the authors and readership will give this monograph careful review when considering the potential carcinogenic effects of asbestos at a population/group level while at the same time recognizing the limitations in drawing inferences about etiology for specific individuals.

References

(1.) Ahmad SM, Sataloff RT. Asbestos exposure and laryngeal cancer: Is there an association? Ear Nose Throat 1 2009;88(10):1140,1142.

(2.) Committee on Asbestos: Selected Health Effects. Laryngeal cancer and asbestos. In: Asbestos: Selected Cancers. Washington, DC: National Academies Press; 2006:173-92.

Erich M. Sturgis, MD, MPH

Associate Professor

Department of Head and Neck Surgery

Department of Epidemiology

The University of Texas M.D. Anderson Cancer Center

Houston

Response:

We thank Dr. Sturgis for bringing this interesting monograph to our attention. It was not indexed or referenced in the sources we searched. While it is certainly worthy of citation and consideration, it also highlights further the problem we addressed in the editorial, particularly the difficulty of conducting research that provides definitive answers to such challenging questions.

The committee documented clearly an association between asbestosis and laryngeal cancer and expressed reasons why a causal relationship seems likely. However, even the committee was careful to avoid declaring causation. The evidence was not strong enough for the report to say that asbestos exposure "causes" laryngeal cancer. Rather, the committee judiciously worded their statement to say that "the evidence is sufficient to infer a causal relationship." I suspect that this wording was selected with care.

The monograph provides interesting data but still does not answer definitively the question of causation in populations or, certainly (as Dr. Sturgis points out), for a specific individual.

We appreciate having this document brought to the attention of our readers and look forward to continued clinical, epidemiologic, and laboratory research leading us to a definitive answer to this important question.

Robert T. Sataloff, MD, DMA, FACS

Editor-in-Chief

EAR, NOSE & THROAT JOURNAL
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Author:Sturgis, Erich M.
Publication:Ear, Nose and Throat Journal
Article Type:Letter to the editor
Date:Mar 1, 2010
Words:599
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