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.