SURVIVAL CHANCE IN PAPILLARY THYROID-CANCER IN HUNGARY - INDIVIDUAL SURVIVAL PROBABILITY ESTIMATION USING THE MARKOV METHOD

Purpose: The typically benign, but occasionally rapidly fatal clinical course of papillary thyroid cancer has raised the need for individual survival probability estimation, to tailor the treatment strategy exc lusively to a given patient. Materials and methods: A retrospective st udy was performed on 400 papillary thyroid cancer patients with a medi an follow-up time of 7.1 years to establish a clinical database for un i-and multivariate analysis of the prognostic factors related to survi val (Kaplan-Meier product limit method and Cox regression). For a more precise prognosis estimation, the effect of the most important clinic al events were then investigated on the basis of a Markov renewal mode l. The basic concept of this approach is that each patient has an indi vidual disease course which (besides the initial clinical categories) is affected by special events, e.g. internal covariates (local/regiona l/distant relapses). On the supposition that these events and the caus e-specific death are influenced by the same biological processes, the parameters of transient survival probability characterizing the speed of the course of the disease for each clinical event and their sequenc e were determined. The individual survival curves for each patient wer e calculated by using these parameters and the independent significant clinical variables selected from multivariate studies, summation of w hich resulted in a mean cause-specific survival function valid for the entire group. On the basis of this Markov model, prediction of the ca use-specific survival probability is possible for extrastudy cases, if it is supposed that the clinical events occur within new patients in the same manner and with the similar probability as within the study p opulation. Results: The patient's age, a distant metastasis at present ation, the extent of the surgical intervention, the primary tumor size and extent (pT), the external irradiation dosage and the degree of TS H suppression proved to be statistically significant and independent p rognostic factors with regard to cause-specific survival in multivaria te studies. During follow-up, 14, 14, 9 and 12% of the patients underw ent local/regional/distant relapses or thyroid cancer-related death, r espectively. Through use of the above six independent clinical variabl es and the parameters relating to the four clinical events and their i nterrelations, mean cause-specific survival probabilities of 88, 83 an d 78% were determined at 10, 20 and 30 years, respectively. The surviv al-predicting software (PATHYPRE) written on the basis of the biostati stical model is available through Internet connections on the home pag e of the National Institute of Oncology, Budapest (www.oncol.hu). Conc lusion: Prediction of the individual survival probability for extrastu dy cases affords a rationale for individualization of the treatment of papillary thyroid cancer patients. (C) 1997 Elsevier Science Ireland Ltd.