Mapping expanded prostate cancer index composite to EQ5D utilities to inform economic evaluations in prostate cancer: Secondary analysis of NRG/RTOG 0415.

The Expanded Prostate Cancer Index Composite (EPIC) is the most commonly used patient reported outcome (PRO) tool in prostate cancer (PC) clinical trials, but health utilities associated with the different health states assessed with this tool are unknown, limiting our ability to perform cost-utility analyses. This study aimed to map EPIC tool to EuroQoL-5D-3L (EQ5D) to generate EQ5D health utilities.

This is a secondary analysis of a prospective, randomized non-inferiority clinical trial, conducted between 04/2006 and 12/2009 at cancer centers across the United States, Canada, and Switzerland. Eligible patients included men >18 years with a known diagnosis of low-risk PC. Patient HRQoL data were collected using EPIC and health utilities were obtained using EQ5D. Data were divided into an estimation sample (n = 765, 70%) and a validation sample (n = 327, 30%). The mapping algorithms that capture the relationship between the instruments were estimated using ordinary least squares (OLS), Tobit, and two-part models. Five-fold cross-validation (in-sample) was used to compare the predictive performance of the estimated models. Final models were selected based on root mean square error (RMSE).

A total of 565 patients in the estimation sample had complete information on both EPIC and EQ5D questionnaires at baseline. Mean observed EQ5D utility was 0.90±0.13 (range: 0.28-1) with 55% of patients in full health. OLS models outperformed their counterpart Tobit and two-part models for all pre-determined model specifications. The best model fit was: "EQ5D utility = 0.248541 + 0.000748*(Urinary Function) + 0.001134*(Urinary Bother) + 0.000968*(Hormonal Function) + 0.004404*(Hormonal Bother)- 0.376487*(Zubrod) + 0.003562*(Urinary Function*Zubrod)"; RMSE was 0.10462.

This is the first study to identify a comprehensive set of mapping algorithms to generate EQ5D utilities from EPIC domain/ sub-domain scores. The study results will help estimate quality-adjusted life-years in PC economic evaluations.

PloS one. 2021 Apr 14*** epublish ***

Rahul Khairnar, Stephanie L Pugh, Howard M Sandler, W Robert Lee, Ester Villalonga Olives, C Daniel Mullins, Francis B Palumbo, Deborah W Bruner, Fadia T Shaya, Soren M Bentzen, Amit B Shah, Shawn C Malone, Jeff M Michalski, Ian S Dayes, Samantha A Seaward, Michele Albert, Adam D Currey, Thomas M Pisansky, Yuhchyau Chen, Eric M Horwitz, Albert S DeNittis, Felix Y Feng, Mark V Mishra

Department of Pharmaceutical Health Services Research, University of Maryland School of Pharmacy, Baltimore, MD, United States of America., NRG Oncology Statistics and Data Management Center, Philadelphia, PA, United States of America., Department of Radiation Oncology, Cedars-Sinai Medical Center, Los Angeles, CA, United States of America., Department of Radiation Oncology, Duke University, Durham, NC, United States of America., Department of Radiation Oncology, Emory University, Atlanta, GA, United States of America., Department of Epidemiology and Public Health, University of Maryland School of Medicine, Baltimore, MD, United States of America., WellSpan Health-York Cancer Center, York, PA, United States of America., Ottawa Hospital and Cancer Center, Ottawa, ON, Canada., Department of Radiation Oncology, Washington University, St. Louis, MO, United States of America., Juravinski Cancer Center at Hamilton Health Sciences, Hamilton, ON, Canada., Kaiser Permanente Northern California, Oakland, CA, United States of America., Saint Anne's Hospital, Fall River, MA, United States of America., Zablocki VAMC and the Medical College of Wisconsin, Milwaukee, WI, United States of America., Department of Radiation Oncology, Mayo Clinic Rochester, Rochester, MN, United States of America., Department of Radiation Oncology, University of Rochester, Rochester, NY, United States of America., Department of Radiation Oncology, Fox Chase Cancer Center, Philadelphia, PA, United States of America., Department of Radiation Oncology, Main Line Health, Philadelphia, PA, United States of America., Department of Radiation Oncology, University of California San Francisco, San Francisco, CA, United States of America., Department of Radiation Oncology, University of Maryland School of Medicine, Baltimore, MD, United States of America.