Multivariate analysis of survival in differentiated thyroid cancer: the prognostic significance of the age factor

A retrospective analysis of tumour and patient characteristics was performed in 202 patients with papillary (n = 132) or follicular (n = 70) thyroid carcinoma, in order to identify prognostic factors related to survival. The following facts were found to be unfavourably related to survival: follicular histology, extrathyroidal growth of the primary tumour (stage pT4), regional lymph node involvement (stages pN1-3), presence of distant metastases at diagnosis (stage pM1), male sex (in papillary cancer) and old age (only death due to thyroid tumour was evaluated). For 190 patients sufficient material was available to permit extensive histopathological investigation. In patients with papillary cancer the presence of small anaplastic foci and/or greater than 25% solid structures (n = 18) was correlated with a reduced survival rate. Our study underlines the importance of distinguishing, histologically, between papillary and follicular cancer and in addition demonstrates the prognostic value of histological grade in papillary (but not follicular) carcinoma. We applied Cox's proportional hazard model to the survival data of these 190 patients and, after stage grouping, found that tumour stage (locoregional vs. advanced disease) was the most important prognostic factor. The second most important factor was the histological (sub)type (well differentiated papillary carcinoma vs. moderately differentiated papillary carcinoma and follicular carcinoma). Age at diagnosis and sex appeared to be of lesser importance. Therefore our study does not recommend the use of age as a guide for therapeutical decisions in differentiated thyroid cancer.