Long-term oncologic outcomes of papillary thyroid microcarcinoma according to the presence of clinically apparent lymph node metastasis: a large retrospective analysis of 5,348 patients

Jung Bum Choi,1,* Woo Kyung Lee,2,3,* Seul Gi Lee,2,4 Haengrang Ryu,5 Cho Rok Lee,4 Sang Wook Kang,4 Jong Ju Jeong,4 Kee-Hyun Nam,4 Eun Jig Lee,2,3 Woong Youn Chung,4 Young Suk Jo,2,3 Jandee Lee4 1Department of Surgery, Pusan National University College of Medicine, Busan, South Korea; 2Brain Korea 21 PLUS Project for Medical Science, Yonsei University, Seoul, South Korea; 3Department of Internal Medicine, Severance Hospital, Yonsei Cancer Center, Yonsei University College of Medicine, Seoul, South Korea; 4Department of Surgery, Open NBI Convergence Technology Research Laboratory, Yonsei Cancer Center, Severance Hospital, Yonsei University College of Medicine, Seoul, South Korea; 5Department of Surgery, Hongik Hospital, Seoul, South Korea *These authors contributed equally to this work Purpose: Active surveillance (AS) of low-risk papillary thyroid microcarcinoma (PTMC) may reduce the risk of overtreatment of clinically insignificant cancer. However, the absence of predictor for the progression of PTMC resulted in treatment delay and potentially compromising cure of aggressive disease. Therefore, to anticipate potential damage of delayed surgery, we investigated the oncologic outcomes of patients with low-risk PTMC initially eligible for AS except clinically apparent lymph node metastasis (LNM), imitating delayed surgery with neck dissection. Materials and methods: A total of 5,348 patients, enrolled between 1987 and 2016, with low-risk PTMC initially eligible for AS were included regardless of LNM. We classified our study patients into two groups: Group I, lobectomy with prophylactic central cervical node dissection; Group II, total thyroidectomy with modified radical neck dissection for LNM. In addition, we investigated the oncological outcomes of patients with second-wave surgery due to lateral lymph node recurrence (Group III, subgroup of Group I). Results: Group I showed more favorable clinicopathological characteristics compared with Group II. In Group I, only 29 (0.58%) of 4,927 patients underwent second-wave surgery with neck dissection for lateral lymph node recurrences, whereas in Group II, all 22 (5.23%) of 421 patients underwent second-wave selective node dissection because of nodal recurrence. Disease-free survival rates were significantly different between Groups I and II (P