Validation of Microsimulation Models against Alternative Model Predictions and Long-Term Colorectal Cancer Incidence and Mortality Outcomes of Randomized Controlled Trials

Abstract

<b>Background</b>. This study aimed to assess the validity of 2 microsimulation models of colorectal cancer (CRC), <i>Policy1-Bowel</i> and <i>ASCCA.</i><b>Methods</b>. The model-estimated CRC risk in population subgroups with different health statuses, "dwell time" (time from incident precancerous polyp to symptomatically detected CRC), and reduction in symptomatically detected CRC incidence after a one-time complete removal of polyps and/or undetected CRC were compared with published findings from 3 well-established models (<i>MISCAN, CRC-SPIN</i>, and <i>SimCRC</i>). Furthermore, 6 randomized controlled trials (RCTs) that provided screening using a guaiac fecal occult blood test (Funen trial, Burgundy trial, and Minnesota Colon Cancer Control Study [MCCCS]) or flexible sigmoidoscopy (NORCCAP, SCORE, and UKFSST) with long-term follow-up were simulated. Model-estimated long-term relative reductions of CRC incidence (RR_<i>inc</i>) and mortality (RR_<i>mort</i>) were compared with the RCTs' findings. <b>Results</b>. The <i>Policy1-Bowel</i> and <i>ASCCA</i> estimates showed more similarities to <i>CRC-SPIN</i> and <i>SimCRC</i>. For example, overall dwell times estimated by <i>Policy1-Bowel</i> (24.0 years) and <i>ASCCA</i> (25.3) were comparable to <i>CRC-SPIN</i> (25.8) and <i>SimCRC</i> (25.2) but higher than <i>MISCAN</i> (10.6). In addition, ∼86% of <i>Policy1-Bowel</i>'s and ∼74% of <i>ASCCA</i>'s estimated RR_<i>inc</i> and RR_<i>mort</i> were consistent with the RCTs' long-term follow-up findings. For example, at 17 to 18 years of follow-up, the MCCCS reported RR_<i>mort</i> of 0.67 (95% confidence interval [CI], 0.51-0.83) and 0.79 (95% CI, 0.62-0.97) for the annual and biennial screening arm, respectively, and the UKFSST reported RR_<i>mort</i> of 0.70 (95% CI, 0.62-0.79) for CRC at all sites and 0.54 (95% CI, 0.46-0.65) for distal CRC. The corresponding model estimates were 0.65, 0.74, 0.81, and 0.61, respectively, for <i>Policy1-Bowel</i> and 0.65, 0.70, 0.75, and 0.58, respectively, for <i>ASCCA</i>. <b>Conclusion</b>. <i>Policy1-Bowel</i> and <i>ASCCA</i>'s estimates are largely consistent with the data included for comparisons, which indicates good model validity.