Papillary thyroid microcarcinoma: Analysis of outcomes and features predicting risk of recurrence.

Abstract

e18569 Background: Papillary thyroid microcarcinoma (PTMC) is an enigmatic entity - diverse opinions exist on its clinical course and management. We aimed to analyse disease outcomes and to identify high-risk factors in PTMCs. Methods: This is a retrospective analysis of patients of PTMC treated in our hospital between 2000 and 2014. Clinico-radiological features, treatment details, long term outcomes and recurrence patterns were noted; these were analysed statistically. Results: 160 patients were studied; 61% were females; 86% were aged 55 years or below; 95% cases presented with an enlarged neck node or thyroid nodule or distant metastasis while 5% were incidentalomas. Total thyroidectomy with radioiodine ablation was done in 77% while hemithyroidectomy was done in 23% patients. Follow up ranged between 2 and 238 months. There were 11 (7%) disease related events (nodal or distant metastases or death due to persistent disease). 4 (2.5%) patients died of disease. On univariate analysis, a larger thyroid primary (p 0.001), pre-operatively radiologically identifiable disease in the thyroid (p 0.02) and the lesion not being an incidentaloma (p 0.01) were associated with development of adverse events. Multivariate analysis confirmed the latter two factors as high risk (p 0.05 and 0.00). Nodal metastasis increased with a larger primary (p 0.001), which was multifocal (p 0.00), bilateral (p 0.01) and showed extrathyroid extension (p 0.00). Distant metastases were related with advanced age (p 0.02), presence of involved nodes (p 0.04), larger primary tumour (p 0.15), multifocal tumour (p 0.17), bilateral foci (p 0.02) and extrathyroidal extension (p 0.06). Correspondingly, Kaplan Meier curves showed a better overall survival (OS) and disease free survival (DFS) with incidentalomas as compared to cases presenting with symptoms (Median OS 84 months vs 78 months; Median DFS 79 months vs 77 months) and cases where the lesion was not seen on radiology (Median OS 80 months vs 76 months; Median DFS 80 months vs 75 months). However neither was significant statistically. Addition of Radioiodine ablation did not confer survival advantage (p 0.6). Conclusions: PTMCs are associated with adverse events despite the size of the primary lesion. Stratification as per the above risk factors can improve event free survival. Conversely, aggressive treatment may be deferred in cases of lesions discovered incidentally or on routine screening.