[Survival potentials of patients with papillary carcinoma of the thyroid gland in Hungary].

The typically benign, but occasionally rapid fatal clinical course of papillary thyroid cancer has raised the need for individual survival probability estimation, to tailor the treatment strategy exclusively to the given patient. A retrospective study was performed on 400 papillary thyroid cancer patients, with a mean follow-up time of 10.3 years, to establish a clinical database for uni- and multivariate analysis of the survival probability-related prognostic factors (Kaplan-Meier product limit method and Cox regression). For a more precise prognosis estimation, in the next step the most important clinical events were investigated and survival functions for each patient were calculated on the basis of a Markov renewal model. The basic concept of this approach is as follows: each patient has an individual disease course, which (besides the initial clinical categories) is affected by special events, e.g. internal covariates (local/regional/distant relapses), that a patient experiences throughout the course of the disease. On the supposition that these events and the cause-specific death are influenced by the same biological process, the parameters of transient survival probability characterizing the speed of the course of the disease for each sequence of clinical events were determined. The individual survival curves for each patients were calculated by using the former parameters and the independent, significant clinical variables, summation of which resulted in an overall cause-specific survival function valid for the entire group. The patient's age, a distant metastasis at presentation, the extent of the surgical intervention, the primary tumour size, the dosage of the external irradiation and the degree of the TSH suppression proved to be statistically significant (in that sequence) and independent prognostic factors as concerns cause-specific survival in multivariate studies. During follow-up 14%, 14%, 9% and 12% of the patients underwent local/regional/distant relapses and thyroid cancer-related death. Through use of the above six independent clinical variables and the parameters relating to the interrelations of the four clinical events, mean cause-specific survival probabilities of 88%, 83% and 78% were determined at 10, 20 and 30 years, respectively. The 30-year individual survival probability prediction for these study cases showed that no cancer-related death occurred > or = 92% (low-risk group), while the tumour-related deaths were considerable (31%) < or = 78% (high-risk group), and there were only 6% deaths in the intermediate-risk group. The constructed survival function permits a prediction of the individual survival probability of extra-study cases under the given treatment conditions and within the given population, and thus affords a rationale for individualization of the treatment of papillary thyroid cancer patients.