Sample size increase during a survival trial when interim results are promising
ABSTRACT This paper is to extend Mehta and Pocock (2011) to provide a way in doing sample size increase in survival trials. Sample space is divided by observed test statistic at interim into three zones: unfavorable, promising, and favorable, within which sample size (required number of events) has a proper increase if falling into the promising zone and otherwise remains unchanged. Simulations with scenarios in the presence/absence of censoring, with/without adaptation, and allowing fourfolds versus twofolds of increase in sample size are compared.