Using 'Costs States' in a Semi-Markov Model to Estimate Cost-Effectiveness: an Illustration for Metastatic HER2 Breast Cancer in the Czech Republic
Abstract
This paper proposes a method for costs estimation by focusing on periods defined by administration of specific treatment. We define states in a semiMarkov model that are associated with specific (repeating) treatment, e.g., regularly administered medication or procedures.
On the contrary, it is common practice to have health states defined based on the health condition of the observed patients, such as progression-free, progression, and death [1]. There are three main advantages of our approach.
It is relatively straightforward to assign costs based on administered procedures. Moreover, our 'costs states' allow us to estimate the periods separately when no treatment is administered.
Furthermore, we also avoid interval censoring that arises when using states defined by changes in health status that can usually only be detected during a check-up [2]. We apply the method of 'costs states' to data drawn from the Czech clinical practice.
These are on treatment of metastatic breast cancer with amplification of human epidermal growth factor 2 protein (HER2+), a very aggressive type of breast cancer. The aim is to assess the cost-effectiveness of adding the pharmaceutical pertuzumab to the combination of trastuzumab and docetaxel within first-line therapy.