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

Jie Bin Lew, Marjolein J.E. Greuter, Michael Caruana, Emily He, Joachim Worthington, D. James St John, Finlay A. Macrae, Eleonora Feletto, Veerle M.H. Coupé, Karen Canfell

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Background. This study aimed to assess the validity of 2 microsimulation models of colorectal cancer (CRC), Policy1-Bowel and ASCCA. 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, and SimCRC). 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 inc) and mortality (RR mort) were compared with the RCTs’ findings. Results. The Policy1-Bowel and ASCCA estimates showed more similarities to CRC-SPIN and SimCRC. For example, overall dwell times estimated by Policy1-Bowel (24.0 years) and ASCCA (25.3) were comparable to CRC-SPIN (25.8) and SimCRC (25.2) but higher than MISCAN (10.6). In addition, ∼86% of Policy1-Bowel’s and ∼74% of ASCCA’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, for Policy1-Bowel and 0.65, 0.70, 0.75, and 0.58, respectively, for ASCCA. Conclusion. Policy1-Bowel and ASCCA’s estimates are largely consistent with the data included for comparisons, which indicates good model validity.

Original languageEnglish
Pages (from-to)815-829
Number of pages15
JournalMedical decision making
Issue number6
Publication statusPublished - 1 Aug 2020


  • Policy1-Bowel
  • colorectal cancer
  • microsimulation
  • population modelling
  • validation

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