Prognostic factors of follicular thyroid carcinoma.

INTRODUCTION Most prognostic studies in differentiated carcinoma have included a high number of papillary carcinomas and few follicular carcinomas, and not all of their conclusions therefore apply to the latter. OBJECTIVE To analyze the prognostic factors of follicular thyroid carcinoma. PATIENTS AND METHODS SELECTION CRITERIA Patients with histological diagnosis of follicular carcinoma who had undergone potentially curative surgery, had no disseminated disease at diagnosis, and had been followed up for at least 5 years. STUDY VARIABLES Tumor recurrence was defined as: 1) tumor lesions with cytological analysis suggesting malignancy and/or 2) patients with total thyroidectomy with thyroglobulin levels >2 ng/mL. Clinical, therapeutic, and histological parameters were analyzed to assess prognostic factors. RESULTS Recurrence was found in 25 (38%) of the 66 study patients during a follow-up period of 99 ± 38 months. Most patients with recurrence (n=20) had increased Tg levels without anatomical location, and were initially treated with radioactive I131. In the remaining 5 cases, surgical excision of the lesion was performed, and three patients required surgery during the follow-up period. Two patients died due to the disease (3%), and two other patients (3%) currently have distant metastases. Mean disease-free interval was 154 ± 14 months, and rates of disease-free patients at 5, 10, 15, and 20 years were 71, 58, 58, and 58% respectively. Clinical factors influencing recurrence included 1) age (p=0.0035); 2) sex (p=0.0114); and 3) cervical pain (p=0.0026). Histological/surgical factors associated with recurrence included 1) infiltration into neighboring structures (p=0.0000); 2) type of carcinoma (p=0.0000); 3) size (p=0.0162); 4) vascular invasion (p=0.0085); and 5) adenopathies (p=0.046). In the multivariate study, cervical pain (p=0.018) and extrathyroid invasion (p=0.045) continued to be significant factors. CONCLUSIONS In follicular carcinoma, rates of disease-free patients are 71% at 5 years and 58% at 10 years, and the main predictive factors are presence of local clinical symptoms and infiltration into neighboring structures.