Multifocality as independent prognostic factor in papillary thyroid cancer - A multivariate analysis.

PURPOSE: The incidence of multifocality of papillary thyroid carcinoma (PTC) ranges from 18 to 87.5% The mechanisms of multifocal spreading, correlation with tumor size, histology variants of PTC, lymph node metastases, and prognostic impact remains unclear. The purpose of this study was to clarify the prognostic significance of multifocality on relapse and survival rates of patients with PTC by analyzing the correlation of multifocality with patient age, gender, tumor size, histological variants of PTC, presence of lymph node metastases and extent of surgery.

METHODS: 153 patients with PTC were included in this study. Patients with pT4 tumors or initially distant metastases were excluded from study. Total thyroidectomy was done in all 153 patients. Central and level III and IV lateral neck lymph node dissection was done in 76.5% of the patients, followed by modified radical neck dissection if positive.

RESULTS: Multifocality was found in 43 (28%) whole thyroid gland specimens, and was significantly more frequent in patients older than 45 years and in tumors greater than 4 cm in diameter (p<0.01). Presence of multifocality didn't significantly correlate with gender, histology variants of PTC or lymph node metastases. In a median follow up of 84 months locoregional relapse occurred in 8.4% and 1.3% of the patients, while 7.2% patients died due to PTC. The incidence of relapse was significantly higher (p<0.01), and relapse free interval and survival were significantly shorter (p=0.0095, p=0.0004, respectively) in patients with multifocal PTC. Cox multivariate regression analysis showed that multifocality was independent prognostic factor for both disease-free interval (DFI) and cancer-specific survival (CSS) of patients with PTC.

CONCLUSION: Due to high incidence of multifocality and potential prognostic impact, total thyroidectomy should be advocated in all patients with PTC, aiming to reduce relapse rate and improve DFI and CSS.