BMC Cancer has published our paper on the impact of differences in polyp detection rates on the effectiveness of stool-based colorectal cancer (CRC) screening. We found that an increase in adenoma detection rate (ADR) gradually reduces CRC burden in a stool-based CRC screening programme whereas an increase in proximal serrated polyp detection rate (PSPDR) only minimally influences long-term outcomes at a population level. This limited effect of the PSPDR can be explained by the limited sensitivity of the stool-based test for serrated polyps.
Background of our study
In 2014, the Netherlands has started with the stepwise implementation of a national colorectal cancer (CRC) screening programme. This programme consists of biennial faecal immunochemical test (FIT) screening in individuals aged 55-75 years. Individuals with a positive test outcome are referred to colonoscopy. Individuals in whom cancer is detected will be treated. If polyps, i.e. benign precursor lesions of CRC, are detected, these will be removed by means of polypectomy. However, the detection rates, both ADR and PSPDR, vary considerably among endoscopists.
It is unclear how variations in detection rate influence CRC screening effectiveness. We therefore aimed to evaluate the effect of variation in these detection rates on the long-term impact of FIT based screening.
Our Adenoma and Serrated pathway to Colorectal CAncer (ASCCA) model was set up to simulate the Dutch screening programme. Besides a ‘no screening scenario’, several screening scenarios varying in ADR and PSPDR were evaluated. Using the available literature on colonoscopy miss rates led to a base-case ADR of 59% and PSPDR of 11%, which were varied with intervals of 3 and 2%.
Compared to no screening, FIT-screening in the base-case scenario reduced long-term mortality with 51.8%. At a fixed PSPDR of 11%, an increase in ADR from 44 to 62% would result in a 10.7% difference in mortality reduction. Using a fixed ADR of 59%, changing the PSPDR from 3 to 15% did not substantially influence long-term mortality (51.0 to 52.3%).
PSPDR only has a limited effect on the effectiveness of FIT-based CRC screening due to the low sensitivity of FIT for serrated polyps. Other triage modalities aiming to detect relevant SPs should be explored.
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