world cancer report - iarc

Stage Intervention Control
I (4 cm) 11 (17.2%) 7 (24.1%)
IV (adjacent structures
involved) 8 (12.5%) 13 (44.8%)
Not known 7 (10.9%) 4 (13.9%)
Total 64 (100%) 29 (100%)
Table 4.19 Oral cancer cases according to stage (and percentage distribution), detected during an Indian
screening trial (1995-1999), compared with an unscreened control population.
ther investigations although the compliance
rates for referral were sub-optimal,
ranging from 54 to 72%. The sensitivity of
visual examination for detecting oral
lesions varied from 58 to 94% and the
specificity from 76 to 98%. In an on-going
randomized controlled oral cancer
ER OC
Fig. 4.51 Oral cancer (OC) arising from a pre-existing
erythroplakia (ER).
Fig. 4.52 Confirmatory examination by a dentist in
a woman referred as “screen positive” after oral
cancer screening in Trivandrum District, Kerala,
India.
screening intervention trial during 1995-
1999 in Trivandrum, South India, involving
115,000 subjects, 60% of oral cancers in
the intervention group were detected in
early stages as opposed to 17% in the
control group (Table 4.19) [7].
An oral cancer screening programme in
Cuba, which has been running since
1984, involves annual oral examination of
subjects aged 15 and above by dentists.
A descriptive evaluation in 1994 revealed
that participation and compliance were
sub-optimal [8]. There has been no
decline in oral cancer incidence and mortality
in Cuba since the initiation of the
programme, though there is limited evidence
for a shift in the stage of cancers
detected, from advanced to early, after
the introduction of screening. In summary,
there is no evidence as yet to establish
that screening with oral visual inspection
can reduce incidence of and mortality
from oral cancer.
Toluidine blue
Toluidine blue dye has been mostly used
as an adjunct for early detection of oral
cancer in selected subjects with precancerous
lesions, in order to provide better
demarcation of malignant and dysplastic
changes so as to help select sites for
biopsies [9]. This test has been evaluated
only in a few specified clinical settings
where the reported false negative and
false positive rates ranged from 20 to
30%. There are no studies investigating
its use in the context of screening. Thus,
the value of visual examination after toluidine
blue application in the early detection
of oral cancer is not known.
Self-screening
There is very little information on selfscreening
for oral cancer or on health
education to promote mouth self-examination,
especially in high-risk population
groups. In a study to evaluate the feasibility
of mouth self-examination in India,
36% of 22,000 subjects who were taught
mouth self-examination reportedly practised
the test and in the 247 subjects visiting
the clinic within two weeks of a promotion
campaign, 89 precancers were
detected and 7 oral cancers [10]. There is
no information available on long-term feasibility
of and detection rates with selfscreening
in oral cancer detection.
Oral cytology
Screening by oral cytology has never
achieved the same recognition or efficacy
as cervical cytology screening. There are
major limitations for oral exfoliative cytology
as a screening modality for oral cancer.
Firstly, the lesion needs to be seen
before a sample can be collected, to
ensure adequate numbers of abnormal
cells. Secondly, only a small number of
cells are identifiable in a smear.
Furthermore, interpretation is of a subjective
nature and there are high false
negative diagnosis rates with leukoplakia
[11,12]. If a lesion can be seen, it may
prove preferable to biopsy it rather than
to take a cytological sample. Thus oral
cytology has received only limited attention
and no adequate information is available
on the utility of this approach for oral
cancer screening.
Implementation
Organization of oral cancer screening
programmes based on visual inspection
of the oral cavity is currently not recommended
as a public health policy for highrisk
countries due to lack of information
on reduction in incidence and mortality,
as well as cost-effectiveness of such an
approach [13]. It is likely that the trial in
Screening for oral cancer
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