Ordered Tests for Right–Censored Survival Data

In comparative clinical trials or animal carcinogenesis studies, the effect of increasing dose levels of an agent or an increasing number of additional modalities are frequently evaluated on the prolonged survival time of patients with a particular disease. It is of particular interest to test the ordered alternative that a treatment level increase leads to better survival. This paper considers an ordered test based on the two–sample weighted Kaplan–Meier statistics (Pepe & Fleming, 1989, 1991). It evaluates asymptotic relative efficiencies of the proposed ordered weighted Kaplan–Meier test, the competing ordered weighted logrank test (Liu et al., 1993) and modified ordered logrank test (Liu & Tsai, 1999) under Lehmann alternatives, for various piecewise exponential survival distributions. Finally, it demonstrates the proposed test on an appropriate dataset.