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

Background. This study aimed to assess the validity of 2 microsimulation models of colorectal cancer (CRC),Policy1-BowelandASCCA.Methods. 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 (MISCAN, CRC-SPIN, andSimCRC). 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 (RRinc) and mortality (RRmort) were compared with the RCTs' findings.Results. ThePolicy1-BowelandASCCAestimates showed more similarities toCRC-SPINandSimCRC. For example, overall dwell times estimated byPolicy1-Bowel(24.0 years) andASCCA(25.3) were comparable toCRC-SPIN(25.8) andSimCRC(25.2) but higher thanMISCAN(10.6). In addition, similar to 86% ofPolicy1-Bowel's and similar to 74% ofASCCA's estimated RR(inc)and RR(mort)were consistent with the RCTs' long-term follow-up findings. For example, at 17 to 18 years of follow-up, the MCCCS reported RR(mort)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(mort)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, forPolicy1-Boweland 0.65, 0.70, 0.75, and 0.58, respectively, forASCCA.Conclusion.Policy1-BowelandASCCA's estimates are largely consistent with the data included for comparisons, which indicates good model validity.