Lunch Seminar MESIO UPC-UB

Lunch Seminar MESIO UPC-UB

Hour:     14:00-15:00 (Pizza and drinks provided!)
Room:    Sala de Juntes de l’FME

Speaker:  Guadalupe Gómez
               Department of Statistics and Operations Research, UPC

Title:        Sample size determination when the hazard ratio is not constant

Abstract:
Standard methods of summarizing the treatment difference in a comparative, randomized clinical study with a specific event time as the primary endpoint (PE) are based on Kaplan-Meier curves, the logrank test and the hazard ratio which is assumed to be approximately constant over time. For designing the study, one usually utilizes an event-driven scheme to determine the sample size and this formulation is, often based, on the proportional hazard (PH) assumption.
In this talk we will discuss sample size determination for the comparison of two groups when the PH does not hold. The starting point is the asymptotic relative efficiency (ARE) method (Gómez and Lagakos, 2013) to derive efficiency guidelines for deciding whether to expand a study primary endpoint from E1 to E* = E1 U E2. The ARE assumes, among other set of realistic assumptions, constant hazard ratios, HR1 and HR2 for E1 and E2 and can be used as a tool to compute the required sample size if E* is chosen as PE.