A piecewise Markov process for analysing survival from breast cancer in different risk groups

A study of the relapse and survival times for 300 breast cancer patients su bmitted to post-surgical treatments is presented. After surgery, these pati ents were given three treatments: chemotherapy; radiotherapy; hormonal ther apy and a combination of them. From the data set, a non-homogeneous Markov model is selected as suitable for the evolution of the disease. The model i s applied considering two time periods during the observation of the cohort where the disease is well differentiated with respect to death and relapse . The effect of the treatments on the patients is introduced into the model via the transition intensity functions. A piecewise Markov process is appl ied, the likelihood function is built and the parameters are estimated, fol lowing a parametric methodological procedure. As a consequence, a survival table for different treatments is given, and survival functions for differe nt treatments are plotted and compared with the corresponding empirical sur vival function. The fit of the different curves is good, and predictions ca n be made on the survival probabilities to post-surgical treatments for dif ferent risk groups. Copyright (C) 2001 John Wiley & Sons, Ltd.