Abstract
We thank Yu et al. for their interest in our study and questions.1Hwang Y. Kang C.H. Park S. et al.Impact of lymph node dissection on thymic malignancies: multi-institutional propensity score matched analysis.J Thorac Oncol. 2018; 13: 1949-1957Abstract Full Text Full Text PDF PubMed Scopus (22) Google Scholar They argued the high rate of lymph node metastasis in thymoma, with an incidence of 6.7% in our study. In their experience, Yu et al.1Hwang Y. Kang C.H. Park S. et al.Impact of lymph node dissection on thymic malignancies: multi-institutional propensity score matched analysis.J Thorac Oncol. 2018; 13: 1949-1957Abstract Full Text Full Text PDF PubMed Scopus (22) Google Scholar could not find any metastasis in any of 417 patients with thymoma. Yu et al.1Hwang Y. Kang C.H. Park S. et al.Impact of lymph node dissection on thymic malignancies: multi-institutional propensity score matched analysis.J Thorac Oncol. 2018; 13: 1949-1957Abstract Full Text Full Text PDF PubMed Scopus (22) Google Scholar insisted that lymph node metastasis in thymoma is a rare phenomenon and should be considered differently from lymph node metastasis in thymic carcinoma, which harbors a relatively high incidence of lymph node metastasis. I think that the argument of Yu et al.1Hwang Y. Kang C.H. Park S. et al.Impact of lymph node dissection on thymic malignancies: multi-institutional propensity score matched analysis.J Thorac Oncol. 2018; 13: 1949-1957Abstract Full Text Full Text PDF PubMed Scopus (22) Google Scholar is reasonable and worth considering. In our study, the overall rate of lymph node metastasis in thymoma was very low (i.e., 1.7% [22 of 1315] patients). The rate increased by up to 6.7% if we included only those patients who underwent routine lymph node dissection (LND). However, we must consider the fact that that those who received routine LND do not represent the whole patient group because those patients had larger-size tumors (5.8 ± 2.7 cm versus 5.1 ± 2.4 cm [p < 0.01]), a higher clinically suggestive nodal metastasis rate (13.7% versus 6.1% [p < 0.01]), and more advanced Masaoka-Koga stages (stage III and IV, 30.1% versus 10.2% [p < 0.01]) than did those patients who did not receive routine LND. This finding means that the relatively high rate of lymph node metastasis in the LND group was partly due to patient selection. We think that routine LND, including in early-stage thymoma, cannot increase the rate of lymph node metastasis significantly and that the overall yield will be meager. Considering the absence of survival advantages in the LND group and low rate of lymph node metastasis in our study, we recommend that LND be performed in only selected patients with advanced thymoma. We expect the indication of LND to be established by further research studies in the future. The Real Situation of Lymph Node Metastases in ThymomaJournal of Thoracic OncologyVol. 14Issue 12PreviewWith interest, we read the article by Hwang et al.1 The authors should be praised for analyzing a relatively large group of patients with thymic malignancies. Furthermore, they made comparisons of the 10-year rate of freedom from recurrence in thymoma and thymic carcinoma after propensity score matching. However, I have serious concerns regarding this study. Full-Text PDF Open Archive
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