Report in English with a Dutch summary (KCE reports 45A)

80 Screening for Colorectal Cancer KCE reports vol.45
The screening guidelines of the American Gastroenterological Association 55
note that (quote) newer guaiac-based and immunochemical tests are available
that have improved sensitivity and appear to maintain acceptable specificity . In
April 2002 the American Cancer Society Colorectal Cancer Advisory Group
concluded that (quote) the evidence showing improved specificity with
immunochemical tests, and the lack of requirements to adhere to dietary
restrictions prior to the test, was sufficiently persuasive to update the guideline
(...) to include the following statement: in comparison with guaiac-based tests
for the detection of occult blood, immunochemical tests are more patientfriendly,
and are likely to be equal or better in sensitivity and specificity 365. The
USPSTF evidence review for its guidelines refers only to guaiac-based tests used
in studies of FOBT screening and mortality outcomes 275. A joint committee
representing the World Health Organization and the World Organization for
Digestive Endoscopy published a report on choice of FOBT for colorectal
cancer screening 197 quoting: The Hemoccult Sensa is the recommended gFOBT
due to low cost, greater sensitivity than Hemoccult II, but better specificity than
rehydrated Hemoccult II. Reliable compliance but poor colonoscopy resources
are more compatible with the higher specificity of Hemoccult II. However, if
compliance is uncertain or unreliable but colonoscopy resources are sufficient,
iFOBT may be considered.
One Chinese controlled study 366, the Jiashan trial, was identified in the New
Zealand systematic review as having compared a once only immunochemical
FOBT test to no screening. All residents of Jiashan County aged 30 years or
older were enrolled in the study, and 21 townships in the county were
randomized to either a screening (n = 10 townships) or control (n = 11
townships) group. Participants in the screened group submitted a one-articleper-slide
stool sample and completed a structured risk-assessment
questionnaire from which their attributive degree value was computed.
According to the study protocol, 4.299 participants were defined as high risk
and underwent diagnostic evaluation with 60-cm FS and, in some cases, an
additional screening with colonoscopy. From 1989 to 1996, cumulative
mortality from colon cancer was 90 (95% CI: 83 - 97) per 100.000 in the
screened group and 83 (95% CI: 76 - 90) per 100.000 in the control group (p =
0,222). Mortality from rectal cancer during this time was 110 (95% CI: 102 -
118) per 100.000 in the screened group, which differed significantly from the
control group mortality rate of 161 (95% CI: 152 - 170) per 100.000 (p =
0.003). The iFOBT was also accompanied with a questionnaire on colorectal
cancer risk factors, making it difficult to interpret the results. The population in
this trial was also younger (40 - 49) than in the guaiac FOBT trials. The only
direct evidence from this trial was that a reduction in rectal cancer may be
achievable using this test.
Three case-control studies of iFOBT screening and CRC incidence or CRC
death have been published by the same corresponding authors in Japan 367. They
found that cases diagnosed with advanced colorectal cancer were significantly
less likely than controls to have been screened within the previous 2 or 3 years.
Similarly, Saito et al 368, 369 found that deaths from CRC were significantly less
likely in those screened with iFOBT versus those not screened. Across studies,
the risk reductions ranged from approximately 40 to 60%. As they did for
gFOBTs when compared to subsequent randomized, controlled trials 370,
available case-control studies of iFOBT screening likely overestimate the actual
benefit.
A recent cluster-randomized trial in Italy aimed at assessing the effect of the
type of fecal occult blood, gFOBT or iFOBT on screening compliance 198