Comparison of the clinicopathologic features and prognosis of bilateral versus unilateral multifocal papillary thyroid cancer: An updated study with more than 2000 consecutive patients

BACKGROUNDBilaterality is common in papillary thyroid cancer (PTC), but its clinical and prognostic implications are still controversial, and it remains unclear whether its behavior is more aggressive than multifocality. METHODSThe clinicopathologic features of 2211 consecutive patients with PTC who underwent surgical treatment at the authors' institute between 1997 and 2011 were reviewed. Among these surgical patients, 425 (19.2%) had bilateral PTCs, and 1786 had unilateral PTCs. The patients who had unilateral PTCs were subdivided into a group with unilateral-multifocal PTCs (210 patients) and a group with solitary PTCs (1576 patients). The 10-year disease-free survival (DFS) rates were calculated to compare the prognosis between groups. B-Raf proto-oncogene, serine/threonine kinase (BRAF) mutation status was examined by direct DNA sequencing. RESULTSPatients who had bilateral PTCs were likely to have larger tumors, higher rates of extrathyroid extension and lymph node metastasis, and more advanced tumor stage than those who had unilateral-multifocal PTCs. Multivariate analysis identified only lymph node metastasis as an independent risk factor for PTC recurrence (P<.001). The 10-year DFS rate for patients with bilateral PTCs was much lower than that for those with unilateral-multifocal and solitary PTCs (78.8% vs 85.7% and 89.3%, respectively; P=.005). It is noteworthy that patients who had bilateral PTCs with lymph node metastasis had the worst prognosis in terms of DFS. Incidence of the BRAF V600E mutation (valine to glutamic acid mutation at position 600) was higher in the bilateral PTC group than that in the unilateral and unilateral-multifocal PTC groups. CONCLUSIONSThe current results provide initial evidence that bilateral PTCs are more aggressive than unilateral-multifocal PTCs, and patients who have bilateral disease have more advanced stage and shorter DFS. The poorer outcome of patients with bilateral PTCs may be caused in part by their high incidence of lymph node metastasis. Cancer 2016;122:198-206. (c) 2015 American Cancer Society. This study provides initial evidence that bilateral papillary thyroid cancers (PTCs) are more aggressive than unilateral-multifocal PTCs. The poorer outcome of patients with bilateral PTCs may be caused in part by their high incidence of lymph node metastasis.