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We read with interest the results of the pilot study in England, which was performed to establish the acceptability and diagnostic performance of screening with the faecal immunochemical test (FIT) over the guaiac faecal occult blood test (gFOBT).1 When comparing gFOBT to FIT, the uptake increased from 59.4% to 66.4%, positivity rate increased from 1.7% to 7.8% (at a cut-off level of 20 µg Hb/g faeces) and colorectal cancer (CRC) detection doubled. Moreover, this report showed that also with FIT cut-off levels above 20 µg Hb/g faeces, improved clinical outcomes can be achieved over gFOBT. However, for a screening programme to be effective, it is a prerequisite to detect cancers in an early stage. Thus far, information on stage distribution of screen-detected CRCs in a population-based FIT screening programme is lacking.
In our study, we collected data on all CRCs detected in patients aged 60–75 years in the Netherlands in 2015 through the Netherlands Cancer Registry. In total, 9437 CRCs were diagnosed in 9301 patients: 3579 (38.5%) patients were diagnosed after a positive FIT in the CRC screening programme (screen-detected), 4506 (48.4%) patients were diagnosed due to symptoms (symptom-detected) and 1216 (13.1%) patients had another mode of detection. Among all patients, 2679 (31.3%) CRCs were detected at stage I, 1827 (21.2%) CRCs at stage II, 2630 (30.6%) CRCs at stage III and 1469 (17.1%) CRCs at stage IV. CRCs stage was unknown for 696 (7.5%) CRCs. Comparison of only screen-detected and symptom-detected CRCs showed that 2349 (66.7%) screen-detected CRCs were detected at an early stage (stages I and II), which was higher than the 1771 (39.8%) symptom-detected CRCs (p<0.001, table 1). Screen-detected cancers were more often diagnosed in the left colon (45.9%) than symptom-detected cancers (31.4%, p<0.001). Figure 1 presents the comparison of screen-detected and symptom-detected CRCs by stage distribution for different subgroups (location, gender, age groups and social economic status). As shown in figure 1, in all subgroups, the screen-detected CRCs had a more favourable stage distribution than the symptom-detected CRCs. This indicates that there is no difference in impact of FIT-based screening on stage distribution among different subgroups.
The more favourable stage distribution of screen-detected CRCs may have two main explanations. The first is simply the earlier detection of cancers by FIT screening, which is the aim. However, it may also be due to overdiagnosis of indolent disease. In this case, screening would simply result in more detection of early-stage disease, without actually reducing the amount of advanced CRCs. Therefore, a more favourable stage distribution of screen-detected versus symptomatic CRCs in itself gives no definitive evidence for future mortality reduction.2 3
On the other hand, stage distribution of the screen-detected CRCs is in line with that observed in randomised controlled trials, which eventually demonstrated a reduction in CRC mortality.4–6 It therefore is expected that the Dutch FIT-based screening programme may also decrease CRC mortality. The observed stage distribution is also in line with other FOBT programmes: the UK gFOBT-based screening programme and the FIT-based screening programme of the Basque country.7 8 In the British sigmoidoscopy trial, the proportion of CRCs detected at an early stage (74%) was slightly higher, but in line with our FIT programme.9
In conclusion, screen-detected CRCs in a FIT-based screening programme are detected more often at an early disease stage than symptom-detected CRCs. As survival rates improve if cancers are detected at an early stage, the first prerequisite for mortality reduction as a result of FIT-based screening is met.
The authors thank the team members of the Dutch LECO working group (National Monitoring and Evaluation of the Colorectal Cancer Screening Programme): EJ Kuipers, FJ van Kemenade, AJ van Vuuren, JMG Bonfrer, H van Veldhuizen, M van Ballegooijen, MGJ Thomeer, M Buskermolen, MF van Velthuysen, I Nagtegaal for their role in the LECO team and their critical review of the manuscript. The authors thank the Netherlands Comprehensive Cancer Organisation for providing the data.
Contributors ET-Z and IL-V were responsible for study coordination. ET-Z, AK, MEvL and IL-V were responsible for the study design and writing the first version of the manuscript. ET-Z, AK, IL-V, MEvL, HJdK, MAE, VEL, ED and MCWS drafted the final manuscript. All authors gave critical revisions on intellectual content of the manuscript and approved the final manuscript.
Funding ET-Z’s work is funded by the Dutch National Institute for Public Health and the Environment (RIVM).
Disclaimer The funder had no role in the data collection, statistical analyses and interpretation of the results of writing the manuscript.
Competing interests None declared.
Ethics approval The data of this study originated from the Netherlands Cancer Registry. Data were supplied anonymously; therefore, ethical approval was not required.
Provenance and peer review Not commissioned; internally peer reviewed.
Data sharing statement The data of this study originated from the Netherlands Cancer Registry. The authors are not owner of the data, therefore no unpublished data are available.
Collaborators LECO working group (National Monitoring and Evaluation of the Colorectal Cancer Screening Programme): EJ Kuipers, FJ van Kemenade, AJ van Vuuren, JMG Bonfrer, H van Veldhuizen, M van Ballegooijen, MGJ Thomeer, M Buskermolen, MF van Velthuysen and I Nagtegaal.
Correction notice This article has been corrected since it published Online First. The collaborators statement has been added.
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