world cancer report - iarc

Abnormal findings in digital rectal
examination of the prostate
Induration of part of the gland
Asymmetry of the gland
A palpable nodule in the gland
Decreased mobility due to fixation of
the gland
Table 4.14 Prostate characteristics indicative of
abnormality in the context of digital rectal examination.
are positive, since the true prevalence of
cancer in any cohort remains unknown
(up to 20% of cancers can be missed).
Continuous research to identify better
markers is necessary, and in this regard
studies of the kallikrein gene family are
ongoing [5]. Prostate-specific membrane
antigen has been seen to offer potential
due to its consistent expression in
prostate cancer, thereby opening possibilities
for its use as a diagnostic, staging
and predictive marker [6].
Development of screening protocols
The fate of patients with advanced stages
of prostate cancer stands in sharp contrast
to the outcome of treatment of
patients with localized stages of the disease.
The introduction of serum PSA
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analysis significantly changed the pattern
of diagnosis of prostate cancer to include
the non-palpable, non-visible tumours
referred to as T1c tumours in the TNM
classification (Box: TNM classification of
malignant tumours, p124). In North
America, Europe and other developed
countries, evidence from the widespread
application of digital rectal examination,
serum PSA determination and subsequent
transrectal ultrasound directed biopsy,
has led to a significant shift in the time of
diagnosis of prostate cancer to the earlier,
confined stages of the disease. Recorded
incidence rates have increased dramatically
as an immediate result of earlier
diagnosis of asymptomatic cancers
through the introduction of PSA testing
(Fig. 4.38). Subsequently, incidence rates
have decreased in some populations, such
as the USA, probably because the proportion
of the population with latent tumours
which can be detected by opportunistic
screening has been exhausted [7].
Digital rectal examination is the simplest,
safest and cheapest means of detecting
prostate cancer provided that the tumour
is localized in the gland. Although
advanced local prostate cancer can be
obvious, only one-third of suspicious
abnormal findings on examination are
actually confirmed as cancer (Table 4.14).
Transrectal ultrasound was introduced as
a possible refinement to digital rectal
examination; prostate cancer may be
detected as a hypo-echoic lesion. Wider
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adoption of the technique has revealed a
false positive level comparable with that
of digital examination, with only about
one-third of all suspicious cases being
confirmed as prostate cancer.
Evidence of outcome
A number of biases may complicate evaluation
of any screening programme, and
prostate cancer screening programmes in
particular. These include lead-time bias,
increasing survival as a consequence of
earlier detection in the natural history of
the disease and sampling that favours
detection of less threatening cancers.
Patient self-selection and overdiagnosis of
preclinical cancers also tend to confuse
outcome analysis. Even in the absence of
trials, uncontrolled studies and the large
numbers of specimens removed at radical
prostatectomy have yielded important
information about screening. These data
indicate the extent to which diagnostic
tests are performed and how such testing
has led to a shift in disease stage at diagnosis
and increased survival rates.
Some national authorities have recommended
screening for the detection of
prostate cancer by performing annual digital
rectal examination and PSA tests,
starting at the age of 50 (45 for high-risk
patients), for men with at least a 10-year
life expectancy [8]. These recommendations
are generally being incorporated into
men’s health care programmes in many
parts of the world. A slight but definite
Fig. 4.38 Trends in the incidence of prostate cancer show a marked increase in many world regions, largely due to improved detection methods.
D.M. Parkin et al. (2001) Eur J Cancer 37, suppl. 8: S4-66.
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Screening for prostate cancer
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