ST 520 Statistical Principles of Clinical Trials - NCSU Statistics ...

CHAPTER 9 ST 520, A. TSIATIS and D. Zhang
• treatment 1 (Intensive CAF)
• treatment 2 (Low dose CAF)
• treatment 3 (Standard dose CAF)
where CAF denotes the combination of Cyclophosphamide, Adriamycin and 5-Fluorouracil. As
well as testing for overall differences in the three treatments, we shall also look at the three
pairwise comparisons.
SAS program:
title "Log-rank test comparing all three treatments";
proc lifetest data=bcancer notable;
time years*censor(0);
strata trt;
run;
Part of the output:
Log-rank test comparing all three treatments
The LIFETEST Procedure
Testing Homogeneity of Survival Curves for years over Strata
Rank Statistics
trt Log-Rank Wilcoxon
1 -21.245 -27171
2 37.653 43166
3 -16.408 -15995
Covariance Matrix for the Log-Rank Statistics
trt 1 2 3
1 120.132 -57.761 -62.371
2 -57.761 114.004 -56.243
3 -62.371 -56.243 118.615
Covariance Matrix for the Wilcoxon Statistics
trt 1 2 3
PAGE 162