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Cost-effectiveness analysis of p53 immunohistochemical testing in stage I and II high-risk endometrial cancer.

e18838 Background: PORTEC-3, a phase III clinical trial comparing adjuvant radiation alone (RT) to combined chemoradiation therapy (CTRT) in patients with high-risk endometrial cancer (EC), demonstrated no benefit with CTRT compared to RT for patients with stage I and II EC. However, a subsequent tumor molecular analysis revealed that individuals with stage I and II high-risk EC with p53 mutations had statistically significantly improved progression-free survival (PFS) and clinically significantly improved overall survival (OS) with combined CTRT. As p53 immunohistochemical (IHC) testing and CTRT adds to cost and toxicity, we sought to evaluate the cost-effectiveness of p53 IHC tumor testing in patients with stage I and II high-risk EC. Methods: A Markov decision model was developed to compare two testing strategies in patients with stage I and II high-risk EC: p53 IHC testing vs. no IHC testing. IHC staining for p53 is an accurate and validated surrogate for TP53 mutational status. As a result, p53 IHC testing alone was used in the decision analysis. Data from PORTEC-3 and the subsequent molecular analysis were used for the base case model parameters, including treatment regimen, PFS, OS, and incidence of p53-mutated tumors. Cost and utility data were derived from the Federal Supply Schedule, the Centers for Medicare and Medicaid Services (CMS) Fee Schedules, the Tufts CEA registry, peer-reviewed literature, and expert input. Data analysis was performed using TreeAge Pro Software, 2021. Effectiveness outcomes included quality-adjusted life-years (QALYs) and incremental cost-effectiveness ratios (ICERs). Sensitivity analyses were performed in order to identify the influence of individual variables on the overall model. Results: When compared to no testing, p53 IHC testing resulted in a cost savings of $471 per patient while providing an additional 0.310 QALYs. Therefore, p53 IHC testing was less expensive and more effective than no IHC testing and was a dominant strategy in this model. In one-way sensitivity analyses, CTRT and RT costs, discount rate, and percentage of p53 mutations detected had the most impact on the model; however, p53 IHC testing remained a cost-saving strategy over all parameter ranges examined. Conclusions: For patients with high-risk stage I and II EC, this analysis suggests that p53 IHC testing is cost-effective compared to no testing in determining the costs and benefits of adjuvant chemotherapy. Although additional studies are warranted, this data provides further support for the role of molecular-based treatment decisions for high-risk stage I and II endometrial cancer.