The Epidemiology of nasopharyngeal carcinoma
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Date
1990-12
Authors
Khoon Chan, Chee M.S.
Journal Title
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Volume Title
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Abstract
Nasopharyngeal carcinoma (NPC) patients have elevated IgG and IgA
antibody titers against the Epstein-Barr viral capsid antigen (VCA) and
the diffuse component of the early antigen complex (EA-D) at diagnosis.
Several studies have implied that the presence of anti-VCA-lgA can be
used as a screening marker for early NPC. To evaluate this further, we
undertook a serologic case-control study based on four serum banks which
together had specimens from over 240,000 persons. Seven cases of
undifferentiated or poorly differentiated NPC were diagnosed in the
period after serum collection ranging from 26 months to 154 months. Two
controls per case matched on serum bank, age, sex, race, and date of
serum collection were selected by a pre-determined random process. For
anti-VCA-IgG, the geometric mean titer for cases (88.3) was
significantly higher than that for controls (75.5) (p < 0.05). The
difference was greatest among the Asian patients. No significant
differences were found for anti-VCA-IgA, anti-EA-D, anti-EA-R or antiEBNA.
No time effects were evident when titers were plotted against
time of blood collection preceding diagnosis. Our results do not
suggest EBV activation in the period preceding NPC diagnosis, nor that
detectable IgA antibody against VCA is a marker for early disease.
key words Nasopharyngeal carcinoma, Epstein-Barr virus, serological
screening
The Epstein-Barr virus (EBV) has been consistently
associated with the occurrence of undifferentiated and
poorly differentiated nasopharyngeal carcinoma (NPC). NPC
patients from around the world, at or following diagnosis,
often have high IgG titers against the viral capsid antigen
(VCA) and the diffuse component of the EBV early antigen
complex (EA-D) but not the restricted (EA-R) (de Schryver et
al., 1969, 1974; Henle, w. et al., 1970, 1973; Lin et al.,
1971; Henderson et al., 1974). In contrast, patients with
carcinomas of the oropharynx or hypopharynx or tumors of the
nasopharynx other than carcinomas usually have much lower
titers. IgA titers against the VCA and the EA-D are also
markedly elevated in the sera and saliva of NPC patients
(Wara et al., 1975; Henle, G. et al., 1977). Elevated
titers against an EBV-specific DNase has also been reported
(Cheng et al., 1980). Nucleic acid hybridization
consistently demonstrated the presence of EBV-DNA in NPC
biopsies (zur Hausen et al., 1970, 1974; Nonoyama et al.,
1973), and specifically in the anaplastic or poorly
differentiated carcinoma cells (Wolf et al., 1973, 1975;
Desgranges et al., 1975). Biopsies from carcinomas at other
sites of the head and neck and from other types of tumors of
the nasopharynx have been mostly negative for EBV-DNA
(Andersson-Anvret et al., 1977). The EBV-associated nuclear
5
antigen (EBNA) is also detected in anaplastic NPC cells, but
not in the lymphoid elements of the tumor (Wolf et al.,
1973, 1975; Huang et al., 1974; Klein et al., 1974;
Desgranges et al., 1975).
These findings have prompted much interest in the
potential of EBV serologic markers -- in particular IgA
antibodies against VCA -- as screening aids in early
detection of NPC (Zeng, 1985). The data on EBV serology
prior to diagnosis is sparse, and the temporal relationship
between altered EBV serological profile and emergence of
disease remains obscure. One clinical report, and three
other studies have yielded conflicting results (Ho et al.,
1978; Lanier et al., 1980; Zeng et al., 1985; Chen et al.,
1985). The purpose of this study is to evaluate the pattern
of pre-diagnosis EBV antibodies in a series of NPC patients.
Description
Keywords
Nasopharyngeal carcinoma , Epstein-Barr virus , Serological screening