One in four cases of colorectal cancer (CRC) detected in a guiac faecal occult blood testing (gFOBT) programme are diagnosed within two years of a negative screening result, a study in the UEG Journal (1) has found, suggesting that gFOBT should be replaced by more sensitive screening methods to improve detection rates.
CRC is the most common type of digestive cancer in Europe (2) and annual incidence is predicted to rise by 12% by 2020 (3).
The observational study was carried out on 772,790 people during the first round of the Scottish Bowel Cancer Screening Programme, in which individuals aged 50-74 years were invited to participate in gFOBT screening over a two year study. Overall uptake of the screening was 54%, and of the 1,979 individuals who were diagnosed with CRC during the study period, 25% of the cases detected were within two years of a negative screening result (interval cancers).
Professor Evelien Dekker, United European Gastroenterology CRC screening expert, comments: "Although there are no universal guidelines on an acceptable interval cancer rate, this study supports the need to switch CRC screening with gFOBT to a more sensitive method, such as faecal immunochemical testing, to help reduce this figure."
Due to its superior analytical technique and adjustable cut-off levels, faecal immunochemical testing (FIT) offers substantial clinical benefits which could help increase CRC detection during screening. Comparative studies between the two faecal tests have been performed and have demonstrated the superiority of FIT over gFOBT screening (4,5). FIT has been fully implemented in some areas of Europe such as France and Slovenia, demonstrating robust results so far. A nationwide programme is currently being rolled out in the Netherlands and other nations are piloting the method too.
As well as its enhanced clinical benefits, utilising FIT has been shown to increase participation rates in CRC screening because the test is easier to perform and typically uses only a single faecal sample instead of the three required in gFOBT (6). "The simplicity of FIT should encourage a larger proportion of the public to undertake CRC screening, which also can help increase the levels early detection to improve survival rates" explains Professor Dekker. "With incidence of CRC expected to rise between now and 2020, implementing FIT across Europe should help increase screening participation rates. In the Netherlands we have experienced a participation rate that is 12% higher for FIT compared to gFOBT."
The Need for Screening:
With 355,436 people (46%) not participating in screening during the Scottish Bowel Cancer Screening Programme, the study also highlighted that 47% cases of CRC arose in these non-participants. This compares to just 28% of patients receiving diagnosis through a screening test, where the cancer is more likely to be detected at an earlier stage (see table below).
Early detection of CRC results in a high survival rate, emphasising the requirement that both an effective screening process and a high uptake of screening should be targeted to identify and treat the disease as early as possible.
Professor Dekker adds: "These findings demonstrate that members of the public should be encouraged to participate in CRC screening and not ignore the potential symptoms of CRC after a negative screening result. Consultation with a doctor is strongly advised if symptoms occur, which include blood in the stool or a persistent change in bowel habits."
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