[R] Coxph: solution for violation of proportional hazards assumption.

John Sorkin jsorkin at grecc.umaryland.edu
Sat Apr 7 22:16:23 CEST 2007

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 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
Baltimore, MD 21201-1524

(Phone) 410-605-7119
(Fax) 410-605-7913 (Please call phone number above prior to faxing)
jsorkin at grecc.umaryland.edu

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