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An adjustment for a post‐randomization variable in the comparison of two treatments for survival
Author(s) -
Heller Glenn
Publication year - 2001
Publication title -
statistics in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.996
H-Index - 183
eISSN - 1097-0258
pISSN - 0277-6715
DOI - 10.1002/sim.968
Subject(s) - randomization , proportional hazards model , randomized controlled trial , survival analysis , statistics , restricted randomization , baseline (sea) , survival function , prognostic variable , medicine , variable (mathematics) , overall survival , econometrics , mathematics , oncology , mathematical analysis , oceanography , geology
A method is proposed to infer the randomized treatment effect on survival after an adjustment for a post‐randomization variable. The post‐randomization variable is made independent of the treatment assignment and is considered a surrogate for baseline prognostic factors. The relationship between the post‐randomization surrogate and baseline prognostic factors for survival is considered smooth, but otherwise unknown. The effect of these factors on survival is modelled using the Cox proportional hazards model with a semi‐parametric relative risk function. Likelihood based estimates and tests for the treatment effect are demonstrated. An example from a randomized clinical trial in cancer illustrates the methodology. Copyright © 2001 John Wiley & Sons, Ltd.