I am trying to run a Cox regression (coxph) to predict survival after surgery
and xray therapy. The model violates the proportionality assumption (tested
using time-dependent covariates). I have tried to use strata to solve the
problem but the stratified model still violates the assumption. Does the
violation of proportionality preclude use of a Kaplan-Meier analysis? Is there
any other possible solution to lack of proportionality that I can try?
John
John Sorkin M.D., Ph.D.
Chief, Biostatistics and Informatics
Baltimore VA Medical Center GRECC,
University of Maryland School of Medicine Claude D. Pepper OAIC,
University of Maryland Clinical Nutrition Research Unit, and
Baltimore VA Center Stroke of Excellence
University of Maryland School of Medicine
Division of Gerontology
Baltimore VA Medical Center
10 North Greene Street
GRECC (BT/18/GR)
Baltimore, MD 21201-1524
(Phone) 410-605-7119
(Fax) 410-605-7913 (Please call phone number above prior to faxing)
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