world cancer report - iarc

poorly known since hypopharyngeal cancer
deaths are often mis-certified as deaths from
cancer of the larynx.
Carcinomas of the salivary glands and
nasopharynx are distinguished from head
and neck cancers at other sites both by epidemiology
and by etiology. Nasopharyngeal
cancer is relatively rare on a world scale
(65,000 new cases per year, or 0.6% of all
cancers), but it has a very distinctive geographic
distribution. Age-standardized incidence
rates are high for populations living in
or originating from Southern China, whilst
populations elsewhere in China, South East
Asia, North Africa, and the Inuits (Eskimos) of
Canada and Alaska, all have moderately elevated
rates (Fig. 5.90). Males are more often
affected than females (sex ratio 2–3:1), and
in most populations, there is a progressive
increase in risk with age. In moderate-risk
populations, however, most notably in North
Africa, there is a peak in incidence in adolescence.
There appears to have been a
decrease in incidence over time in some
high-risk populations (e.g. Hong Kong).
Etiology
Smoking and drinking are the major risk factors
for head and neck cancer in developed
countries, in the Caribbean and in South
American countries [1-3]. Smoking is estimated
to be responsible for about 41% of
laryngeal and oral/pharyngeal cancers in
men, and 15% in women worldwide and
these proportions vary amongst different
populations. Tobacco smoking has also been
found to be an important risk factor for
nasopharyngeal cancer in otherwise low-risk
populations. These risk factors have been
shown, for laryngeal and oropharyngeal cancers,
to have a joint “multiplicative” or synergistic
effect.
In the Indian subcontinent, chewing tobacco
in the form of betel quid (a combination of
betel leaf, slaked lime, areca-nut and tobacco
with or without other condiments), bidi (a
locally hand-rolled cigarette of dried temburni
leaf containing coarse tobacco) smoking
and drinking locally brewed crude alcoholic
drinks are the major causative factors.
The role of betel quids without tobacco is not
clear, though a recent case-control study
from Pakistan reported a high risk of oral
cancer [4]. Reverse smoking (in which the lit
Fig. 5.89 The global incidence of cancer of the larynx in men. High-risk countries are found in Southern
and Eastern Europe, Latin America and Western Asia.
end of the cigarette is placed in the mouth so
that an intense heat is experienced) is a risk
factor for cancer of the hard palate. Oral
snuff use is an emerging risk factor for oral
cancer, particularly among young males in
the USA.
A generally impoverished diet, particularly
lacking in vegetables and fruits, is another
risk factor for oral cancer [5]. Consistently,
studies also indicate a protective effect of a
diet rich in vegetables and fruits (20-60%
reduction in risk). A high intake of salted fish
and meat and the release of nitrosamines on
cooking such foods have been linked to
nasopharyngeal cancer in endemic regions.
Oral human papillomavirus (HPV) infection
(transmitted sexually or perinatally) is associated
with an increased risk of head and neck
squamous cell carcinoma development [6].
Overall estimates for HPV prevalence in head
and neck squamous cell carcinoma are very
variable, ranging from 8-100%, but an unusual
laryngeal pathologic subtype, verrucous
laryngeal carcinoma, has a 100% prevalence
of HPV. Tumours of the oropharynx (and in
particular, tonsillar tissue) have been found
to be three times more likely to be HPV-positive
than tumours at other head and neck
sites. Women with a history of in situ or inva-
< 2.4 < 3.7 < 5.8 < 8.5
Age-standardized incidence/100,000 population
< 20.1
sive cervical carcinoma have a two to fourfold
increased risk of oral or laryngeal cancer,
in addition to increased risks of other cancers
associated with HPV. Additional risk factors
implicated in cancer of the larynx include
chronic laryngitis, chronic gastric reflux and
exposure to wood dust, asbestos or ionizing
radiation.
Infection with Epstein-Barr virus is important
in the etiology of nasopharyngeal cancer.
This virus is not found in normal epithelial
cells of the nasopharynx, but is present in all
nasopharyngeal tumour cells, and even in
dysplastic precursor lesions [7] (Chronic
infections, p56).
Detection
Although many head and neck cancers arise
in anatomically accessible areas, delayed
diagnosis is common. Symptoms of oral cancer
include pain, bleeding, difficulty in opening
the mouth, chewing, swallowing and
speech, and a swelling in the neck. Early
lesions are often painless and present as
slightly elevated, velvety red mucosal patches,
as punctate lesions, or as indurated small
ulcers or growths. In more advanced stages,
a large ulceroproliferative mass, with areas of
necrosis, and extension to neighbouring
Head and neck cancer
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