# Kaplan-Meier (tertile) plots

A Kaplan-Meier plot [Kaplan & Meier 1958 J. Amer. Statist. Assoc. 53:457] shows the survival of patient subgroups over time. For tertile-based grouping, the cohort of patients is split into three equal portions (tertiles) according to their marker expression scores. This is done separately for each marker. Where cohorts have a number of patients not exactly divisible by three, the groups will have slightly different numbers. This will also occur if more than a third of patients share the same score (as may be the case for categorical scoring).

The difference in survival between the groups is tested for significance using the log-rank (Mantel-Cox) test [Mantel 1966 Cancer Chemother. Rep. 50:163].

**Available for:** continuous scoring

## [Top]Viewing the results

See accessing and interpreting survival analysis results.

## [Top]Example output

**Figure 1:** Example Kaplan-Meier plot based on marker score tertiles.