Prognostic impact of the number of involved lymph node stations in patients with completely resected non-small cell lung
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ORIGINAL ARTICLE
Prognostic impact of the number of involved lymph node stations in patients with completely resected non‑small cell lung cancer: a proposal for future revisions of the N classification Hideaki Kojima1,2 · Yukihiro Terada1 · Yoshiyuki Yasuura1 · Hayato Konno1 · Tetsuya Mizuno1 · Mitsuhiro Isaka1 · Kazuhito Funai2 · Yasuhisa Ohde1 Received: 17 March 2020 / Accepted: 12 May 2020 © The Japanese Association for Thoracic Surgery 2020
Abstract Objective The current nodal staging for lung cancer is defined only by the anatomical site of metastasis. However, the International Association for the Study of Lung Cancer (IASLC) proposed further subdivisions of the N descriptor that considers the locations and numbers of involved lymph node stations. This study aimed to test the new IASLC categories and compare their prognostic abilities to those of our proposed model that considers only the number of involved lymph node stations instead of the sites of metastasis. Methods Between September 2002 and December 2016, 1581 patients who underwent complete resection for pathologically diagnosed Tis-4N0-2M0 non-small cell lung cancer were retrospectively analyzed. We evaluated the survival rates according to the patients’ N classification as recently proposed by the IASLC and by the number of involved lymph node stations, and determined the optimal N classification. Results The 5-year survival rates for patients with IASLC stages N1a, N1b, N2a1, N2a2, and N2b were 71.5%, 49.9%, 73.7%, 62.1%, and 46.9%, respectively. These results showed relatively good categorizations; however, some prognostic overlaps existed and not all differences were significant. After redefining the number of involved stations as Nα for 1, Nβ for 2–3, and Nγ for ≥ 4 without considering the metastasis sites, the 5-year survival rates for patients in these categories were 72.1%, 58.3%, and 29.6%, respectively; the differences between them were significant. Conclusion The number of involved lymph node stations is a more accurate prognostic indicator in patients with completely resected non-small cell lung cancer. Keywords Non-small cell lung cancer · Lung cancer staging · N descriptor · Lymph node metastasis · Lymph node station
Introduction The tumor–node–metastasis (TNM) classification is the most important determinant of cancer stage, and the accurate evaluation of lymph node metastasis is critical for deciding on the therapeutic strategy for patients with non-small cell lung cancer (NSCLC) [1]. In the 8th edition of the TNM * Hideaki Kojima [email protected] 1
Division of Thoracic Surgery, Shizuoka Cancer Center, 1007 Shimonagakubo, Nagaizumi‑cho, Sunto‑gun, Shizuoka 411‑8777, Japan
First Department of Surgery, Hamamatsu University School of Medicine, Shizuoka, Japan
2
classification, the N classification criterion has remained the same as in the 7th edition, and it is based only on the lymph node’s anatomical location without reflecting the number of lymph node metastases [2, 3]. However, in other organs such as the gastroin
