In a population-based study conducted in nine European countries for which data on mode of detection were available (Belgium, Denmark, England, France, Italy, Ireland, the Netherlands, Slovenia, and Spain), the proportion of colorectal cancer cases detected by screening varied widely between countries. However, in all countries, screen-detected cancers had a more favorable stage distribution than cancers detected otherwise. These findings were published by Cardoso et al in The Lancet Gastroenterology & Hepatology.

Population-Based Study

In describing the study background, the authors wrote that the effects of recently implemented screening programs for colorectal cancer in Europe on colorectal cancer mortality will take several years to be fully understood. The study team aimed to analyze the characteristics and parameters of screening programs, proportions of colorectal cancers detected through screening, and stage distribution in screen-detected and non–screen-detected colorectal cancers. They conducted a population-based study with data from 16 population-based cancer registries.

Patients were included if they were diagnosed with colorectal cancer from the year that organized colorectal cancer screening programs were implemented in each country until the latest year with available data at the time of analysis, and if 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 pathologic TNM information based on the edition in place at time of diagnosis; and mode of detection. If stage information was not available, patients were not included in stage-specific analyses. The primary outcome was proportion and stage distribution of screen-detected vs non–screen-detected colorectal cancers.

Findings

In total, 228,667 colorectal cancer cases were included in this analysis. Proportions of screen-detected cancers varied widely across countries and regions; the highest proportions (40%–60%) were found in Slovenia and the Basque Country in Spain, where fecal immunochemical test–based programs were fully rolled out and participation rates were higher than 50%. A similar proportion of screen-detected cancers was also found for the Netherlands in 2015, where participation was over 70%, even though the program had not yet been fully rolled out to all age groups. In most other countries and regions, proportions of screen-detected cancers were below 30%.

Compared with non–screen-detected cancers, screen-detected cancers were much more often found in the distal colon (range = 34.5%–51.1% for screen-detected vs 26.4%–35.7% for non–screen-detected) and less often in the proximal colon (19.5%–29.9% vs 24.9–32.8%, with P ≤ .02 for each country), and were more often detected at stage I (35.7%–52.7% vs 13.2%–24.9%) and less often at stage IV (5.8%–12.5% vs 22.5%–31.9%, P < .0001).

The study authors concluded, “The proportion of colorectal cancer cases detected by screening varied widely between countries. However, in all countries, screen-detected cancers had a more favorable stage distribution than cancers detected otherwise. There is still much need and scope for improving early detection of cancer across all segments of the colorectum, and particularly in the proximal colon and rectum.”

Disclosure: The study was funded by Deutsche Krebshilfe. For full disclosures of the study authors, visit thelancet.com.