Proportion and stage distribution of screened and unscreened colorectal cancers in nine European countries: an international population-based study

Background

The effects of colorectal cancer screening programs recently introduced in Europe on colorectal cancer mortality will take several years to be fully understood. Our objective was to analyze the characteristics and parameters of screening programs, the proportions of colorectal cancers detected by screening, and the stage distribution in colorectal cancers detected and not detected by screening in order to provide a timely assessment of the potential effects of the programs. testing in several European countries. countries.

Methods

We conducted this population-based study in nine European countries for which data on the mode of detection were available (Belgium, Denmark, England, France, Italy, Ireland, the Netherlands, Slovenia and Spain). Data from 16 population-based cancer registries were included. Patients were included if they had been diagnosed with colorectal cancer from the year in which organized colorectal cancer screening programs were established in each country until the latest year for which data were available at the time. of the analysis, and whether their age at diagnosis fell within the age groups targeted by the programs. Data collected included sex, age at diagnosis, date of diagnosis, topography, morphology, clinical and pathological TNM information based on editing in place at diagnosis, and mode of detection (c i.e. screening detected or not detected). If stage information was not available, patients were not included in stage-specific analyses. The primary endpoint was the proportion and stage distribution of colorectal cancers detected by screening compared to undetected colorectal cancers.

Results

228,667 cases of colorectal cancer were included in the analyses. The proportions of cancers detected by screening varied considerably between countries and regions. The highest proportions (40-60%) were observed in Slovenia and the Basque Country in Spain, where FIT-based programs were fully rolled out and participation rates were above 50%. A similar proportion of cancers detected by screening was also seen in the Netherlands in 2015, where participation was over 70%, although the program had not yet been fully rolled out across all age groups. In most other countries and regions, the proportions of cancers detected by screening were below 30%. Compared to cancers not detected by screening, cancers detected by screening were significantly more often found in the distal colon (range of 34 5 to 51 1% screening vs. 26 4–35 7% unscreened) and less often in the proximal colon (19 5–29 9% screened vs. 24 9–32 8% no screen detected) p≤0 02 for each country, more often at Stage I (35 7–52 7% screen detected vs. 13 2–24 9% not detected by screening), and less often at stage IV (5 8 – 12 5% screening detected
vs. 22 5–31 9% undetected per screen) p

Interpretation

The proportion of colorectal cancer cases detected by screening varied considerably between countries. However, in all countries, cancers detected by screening had a more favorable stage distribution than cancers detected otherwise. There are still many needs and opportunities for improving the early detection of cancer in all segments of the colon and especially in the proximal colon and rectum.

Funding

Deutsche Krebshilfe.

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