Although the decision tree analysis format is invaluable in characterizing a range of clinical trial formulation possibilities, the modeling can become extremely complex as the number of event and decision nodes increases. Thus, while the operational model developed allows the user to enter customized cost scenarios in a certain therapeutic area, it does not allow for changes in the number of decision or event nodes.
We developed the operational model in Microsoft Excel™ for ease of use and sharing, with a user interface coded in Visual Basic. The model is structured such that the user makes all selections through a guided user form, which enables the user to input project-specific values while the underlying worksheets and cost aggregation formula are protected from editing. The interface is designed to allow the user to compare a “custom” scenario, utilizing the values that he has entered in the user form, to a “default” scenario, which draws on average clinical trial costs and other parameters from the literature and data provided by Medidata Solutions (described in greater detail below). The model also allows for a blend of default and custom values as may be desired by the user. Further details on the uses and features of the model can be found in Appendix C.