You have not given enough information to reproduce your problem, so it is difficult to say. Most of the time results such as you display will be due to a data error. It is possible to get a crossing result, however. subject 1 2 3 4 5 ----------------------------- Death 10 - - - 4 Relapse 2 - 4 - 3 Last FU 10 6 6 11 4
The Kaplan-Meier curves are time relapse death 2 4/5 1 3 4/5*3/4 1 4 4/5* 3/4 * 2/3=.4 2/3 10 .4 2/3 * 1/2 = .3333 Subject 1 has a relapse early when all 5 are still at risk, dropping the curve by .2 units. Their death is late when only 2 are at risk, dropping the curve by 1/2. This crossing anomaly usually only happens near the end of a Kaplan-Meier, when the confidence intervals are as wide as a river. Terry Therneau ------------ begin included message -------------------------- At year 5, in group C2 I have one more patient with an event when looking at DFS (13) than when looking at relapse (12). However, the probability is higher when looking at DFS (0.23) than relapse (0.18), which I cannot understand as I have one more event. ______________________________________________ [email protected] mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
