A counting process approach to the analysis of the course of non-Hodgkin's lymphoma

Non-Hodgkin's lymphoma is a neoplastic disease with a course including remission and relapse. Therefore, a mortality analysis of overall survival time alone may conceal important differences between the forces of mortality (hazard functions) associated with distinct states of active disease, for example pre-remission state and first relapse. Further, prognostic factors for overall survival time may fail to contribute significantly to the pre-remission force of mortality. Our approach to analysis is based on a non-homogeneous Markov illness-death process as a stochastic model of the course of disease. It exploits the statistical theory of counting processes.