Different features of pulmonary metastases in differentiated thyroid cancer: natural history and multivariate statistical analysis of prognostic variables.

We studied 134 patients with differentiated thyroid cancer and pulmonary metastases. All were treated with total or near total thyroidectomy, radioiodine and L-thyroxine. The prognostic value of the following variables in three groups of patients were evaluated by univariate and multivariate analysis: age at diagnosis, sex, histologic type, tumor extension, cervical lymph node metastases, mediastinic metastases, presence of metastases in distant sites other than lungs (multiple distant metastases) and morphological (chest x-rays) and functional (131I uptake) features of lung metastases. Univariate analysis identified patient age (p < 0.0001), morphological and functional features of lung metastases (p < 0.0001), presence of multiple distant metastases (p < 0.0001) and histologic type (p = 0.04) as significant prognostic factors. Multivariate analysis showed only morphological (p = 0.0014) and functional (p < 0.0001) features of lung metastases and the presence of multiple distant metastases (p = 0.01) as significant and independent variables. The data show that early (pre-radiological) scintigraphic diagnosis and 131I therapy of lung metastases appear to be the most important elements in obtaining both a significant improvement in survival rate and a prolonged disease-free time interval in these patients.