Modeling the Adenoma and Serrated Pathway to Colorectal CAncer (ASCCA)

Abstract

Several colorectal cancer (CRC) screening models have been developed describing the progression of adenomas to CRC. Currently, there is increasing evidence that serrated lesions can also develop into CRC. It is not clear whether screening tests have the same test characteristics for serrated lesions as for adenomas, but lower sensitivities have been suggested. Models that ignore this type of colorectal lesions may provide overly optimistic predictions of the screen-induced reduction in CRC incidence. To address this issue, we have developed the Adenoma and Serrated pathway to Colorectal CAncer (ASCCA) model that includes the adenoma-carcinoma pathway and the serrated pathway to CRC as well as characteristics of colorectal lesions. The model structure and the calibration procedure are described in detail. Calibration resulted in 19 parameter sets for the adenoma-carcinoma pathway and 13 for the serrated pathway that match the age- and sex-specific adenoma and serrated lesion prevalence in the COlonoscopy versus COlonography Screening (COCOS) trial, Dutch CRC incidence and mortality rates, and a number of other intermediate outcomes concerning characteristics of colorectal lesions. As an example, we simulated outcomes for a biennial fecal immunochemical test screening program and a hypothetical one-time colonoscopy screening program. Inclusion of the serrated pathway influenced the predicted effectiveness of screening when serrated lesions are associated with lower screening test sensitivity or when they are not removed. To our knowledge, this is the first model that explicitly includes the serrated pathway and characteristics of colorectal lesions. It is suitable for the evaluation of the (cost)effectiveness of potential screening strategies for CRC.

Evaluation of the benefits, harms and cost‐effectiveness of potential alternatives to iFOBT testing for colorectal cancer screening in Australia

“…It was adapted from an existing colorectal cancer natural history model, the Adenoma and Serrated pathway to Colorectal CAncer (ASCCA) model 20 and was extensively re-calibrated jointly to the original natural history data 21 and the Australian setting. The model simulates both the adenoma-carcinoma pathway and the serrated pathway in colorectal cancer development, assuming 15% of colorectal cancers are attributable to the serrated pathway.…”

Estimating the Effect of Targeted Screening Strategies

“…Several other colorectal cancer simulation models have previously been published 23-28 and used for evaluation of screening programs (e.g., Greuter et al 29 using the ASCCA 24 model or Zauber 30 using the MISCAN 31 and simCRC 32 models). While the specific predictions of the model may differ, both in terms of cancer risks and the effects of different screening methods, I expect that for comparing different methods of analysis, any realistic model would produce similar results.…”

The potential of imaging techniques as a screening tool for colorectal cancer: a cost-effectiveness analysis

“…35 A detailed description of this calibration has been published previously. 26 Costs Costs related to screening and treatment of CRC are shown in Table 2, together with the source of each item. All costs were converted to 2014 Euros using the consumer price index for that year.…”

“…CAncer model All analyses were conducted using the ASCCA model, 26 which is described in more detail in the Appendix A. A flowchart of the adenoma-carcinoma pathway as simulated by the model is provided in Figure 1.…”

“…26 We also included faecal immunochemical testing (FIT) as a comparator because many countries have implemented stool-based testing. Various strategies differing in screening interval and number of screening rounds were evaluated.…”