Figure 1

The figure shows as an example, the calculated curves of median survival where the age at operation is 45 years. The three curves show similar relations between the median survival and the Ki67 index. The curve of the Cox regression is a step function and from the figure it is apparent that this is a weakness when it is applied to individual patients. The Poisson regression with nonproportional hazard, which includes interaction between Ki67 index and time, does not differ significantly from the simpler Poisson model. By use of the Poisson regression result, the median survival of individual patients can be calculated. The variables entered in the three regression curves were original data from the studied population.