Nature Of This Cancer Type

Cancers of the pharynx are frequently grouped with head and neck cancers, which also include the oral and nasal cavities. The pharynx itself spans several sublocations the oropharynx (ICD-9 146 ICD-O-3 C09-C10), the nasopharynx (ICD-9 147 ICD-O-3 C11), and the hypopharynx (ICD-9 148 ICD-O-3 C12-C13.9). Each of those can be further subdivided (for example, the tonsil is located within the oropharynx), and the more specific locations have somewhat differing characteristics in terms of etio-logic...

Committee Findings

The committee reviewed the evidence from epidemiologic studies and from toxicologic investigations, both animal and in vitro, specifically for each cancer site. The reviews of the evidence related to mineralogy of asbestos and to its carcinogenicity were considered to be generally relevant for all sites, particularly in regard to the causal criterion of coherence or biologic plausibility. There has been ongoing discussion as to whether there is an absolute difference in the toxicity of the...

References

Battista G, Belli S, Comba P, Fiumalbi C, Grignoli M, Loi F, Orsi D, Paredes I. 1999. Mortality due to asbestos-related causes among railway carriage construction and repair workers. Occupation Medicine (London) 49(8) 536-539. Berrino F, Richiardi L, Boffetta P, Esteve J, Belletti I, Raymond L, Troschel L, Pisani P, Zubiri L, Ascunce N, Guberan E, Tuyns A, Terracini B, Merletti F. 2003. Occupation and larynx and hypopharynx cancer A job-exposure matrix approach in an international case-control...

Criteria For Evidence Evaluation Fiber Type

The committee recognized that there is evidence suggesting that the risk associated with asbestos exposure for development of mesothelioma (and possibly of lung cancer) may vary by fiber type. Controversy continues (for example, Hessel et al. 2004, Rice and Heineman 2003) as to whether there is an absolute difference in the toxicity of amphibole and serpentine (chryso-tile only) forms of asbestos and whether only amphibole fibers have carcinogenic potential, particularly for mesothelioma, the...

Info

FIGURE 7.2 Cohort studies RR of pharyngeal cancer in people with any exposure to asbestos compared with people who report none. are plots of relative risks (RRs) for overall exposure and for exposure-response gradients from the cohort studies reviewed. There were 16 cohort populations that had reported findings for this rare cause of death. The strongest evidence of an association comes from a study of insulation workers (Selikoff and Seidman 1991) with a standardized mortality ratio (SMR) of...

Fibrous And Asbestiform

Many minerals may occur as small particles, including particles in the respirable size range, which is less than about 10 m in aerodynamic diameter. Of these, some may include particles with aspect ratios (length diameter) of 5 1 or more, usually reflecting a characteristic of the underlying crystal structure. For example, asbestiform amphiboles have fibers that are elongate parallel to the underlying silicate chains in the structure. Fibrous is a term applied to minerals that consist of...

Study Designs

Epidemiologic designs applied in investigations of environmental and occupational risk factors for cancer are primarily of three types cohort studies of defined groups (such as worker populations), case-control studies, and ecologic studies that compare rates in geographic regions defined by exposure characteristics. Epidemiologic studies can also be classified as exposure-based or general-population-based depending on whether the source population is defined as an exposed group (such as...

Integration Of Epidemiologic Evidence With Nonepidemiologic Evidence

Results from epidemiologic studies of both cohort and case-control designs constitute an important component, but not the only type of evidence considered in the approach applied in Chapters 7-11 to assess the likelihood and strength of causal associations between asbestos and cancer at the selected sites. The committee's strategy for integrating all the evidence closely follows that used by the surgeon general's report on health risks related to tobacco-smoking HHS 2004 . To illustrate, we...