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Estimating survival distributions for two-stage adaptive treatment strategies: A simulation study
Communications for Statistical Applications and Methods 2021;28:411-424
Published online September 30, 2021
© 2021 Korean Statistical Society.

Sifiso Vilakati1,a, Giuliana Corteseb, Thembelihle Dlaminic

aDepartment of Statistics and Demography, University of Eswatini, Eswatini;
bDepartment of Statistical Sciences, University of Padua, Italy;
cDepartment of Electrical and Electronic Engineering, University of Eswatini, Eswatini
Correspondence to: 1 Department of Statistics and Demography, University of Eswatini, Private Bag 4, Kwaluseni, M201, Eswatini. E-mail: sifemman@gmail.com
Received October 10, 2020; Revised July 14, 2021; Accepted July 15, 2021.
 Abstract
Inference following two-stage adaptive designs (also known as two-stage randomization designs) with survival endpoints usually focuses on estimating and comparing survival distributions for the different treatment strategies. The aim is to identify the treatment strategy(ies) that leads to better survival of the patients. The objectives of this study were to assess the performance three commonly cited methods for estimating survival distributions in two-stage randomization designs. We review three non-parametric methods for estimating survival distributions in two-stage adaptive designs and compare their performance using simulation studies. The simulation studies show that the method based on the marginal mean model is badly affected by high censoring rates and response rate. The other two methods which are natural extensions of the Nelson-Aalen estimator and the Kaplan-Meier estimator have similar performance. These two methods yield survival estimates which have less bias and more precise than the marginal mean model even in cases of small sample sizes. The weighted versions of the Nelson-Aalen and the Kaplan-Meier estimators are less affected by high censoring rates and low response rates. The bias of the method based on the marginal mean model increases rapidly with increase in censoring rate compared to the other two methods. We apply the three methods to a leukemia clinical trial dataset and also compare the results.
Keywords : non-parametric methods, two-stage adaptive designs, survival distributions