Diagnostic effectiveness of a complex of measures directed at early detection of colorectal cancer.

<jats:p>Colorectal cancer (CRC) remains one of the leading causes of cancer morbidity and mortality in the Russian Federation and worldwide. The authors of this study previously developed and validated a comprehensive organizational and diagnostic program aimed at the early detection of CRC in the Samara Region, with initial results published in earlier works. However, a long-term assessment of the diagnostic effectiveness of the implemented regional model – based on the transition from a qualitative to a quantitative fecal immunochemical test (iFOBT) for occult blood and digital patient routing-requires a detailed epidemiological analysis over an extended observation period. Objective: to conduct a comparative evaluation of the diagnostic effectiveness of a two-stage CRC screening model in the Samara Region during the periods of qualitative occult blood testing (2018–2022) and quantitative immunochemical testing within the upgraded organizational model (2023–2025). Materials and methods. A retrospective analysis was performed using data from the Samara Region Unified Medical Information and Analytical System (GIS SO EMIAS) and regional oncology registries from 2018 to 2025. The study included data on 2,129,550 screening fecal occult blood tests conducted in individuals aged 40–75 years. Assessed parameters included target population coverage, proportion of positive screening tests, detection rate of confirmed CRC cases per 1,000 screened individuals, and tumor stage distribution (TNM). Statistical analysis employed the Chi-square (χ²) test with Yates’ correction, the Mann–Whitney U test for non-parametric data, and calculation of relative risk (RR) with 95% confidence intervals (CI). Results. The transition to the quantitative iFOBT method in 2023 led to a statistically significant increase in the proportion of positive tests from a mean of 0.37% (range: 0.29–0.44%) in 2018–2022 to 5.59% (range: 5.13–7.18%) in 2023–2025 (χ² = 12,847.3; p &lt; 0.0001). The CRC detection rate rose from 0.26 to 1.85 per 1,000 screened individuals (a 7.1-fold increase; p &lt; 0.001). The absolute number of newly diagnosed CRC cases over the three years of the new model implementation reached 1,072, which is 2.6 times higher than the 417 cases recorded during the preceding five-year period. A key achievement was the favorable shift in stage distribution: the proportion of stage I–II tumors increased from 39.57% to 70.24% (χ² = 214.6; p &lt; 0.001). Resource utilization efficiency improved markedly: the number of tests required to detect one case of early-stage CRC decreased from 9,389 in the previous model to 771 in the new model (a 12-fold increase in efficiency). Conclusion. Implementation of the regional CRC screening model, founded on quantitative immunochemical testing and seamless digital patient routing, demonstrates high diagnostic effectiveness. The model ensures a substantial increase in the detection of CRC at early, curable stages while optimizing healthcare resource utilization. These findings support the scalability of this approach and its integration into federal oncology screening guidelines.</jats:p>