Reasonable extent of lymph node dissection in intentional segmentectomy for small-sized peripheral non-small-cell lung cancer: From the clinicopathological findings of patients who underwent lobectomy with systematic lymph node dissection

INTRODUCTION: Currently, randomized clinical trials to evaluate segmentectomy compared with lobectomy for peripheral cT1aN0M0 non-small-cell lung cancer (NSCLC) are ongoing. During segmentectomy, some lobar-segmental lymph nodes (LSNs) can be difficult to resect for anatomical reasons. The purpose of this study was to clarify the reasonable extent of dissection during intentional segmentectomy for peripheral cT1aN0M0 NSCLC. METHODS: We reviewed the records of patients who underwent lobectomies and systematic lymph node dissections for cT1aN0M0 NSCLC from 1992 to 2009. Among them, a total of 307 patients whose primary nodule was located in the outer third peripheral lung field on thin-section computed tomography (TSCT), and who could be candidates for intentional segmentectomy were enrolled in this study. We analyzed the clinical and radiological factors, which may predict nodal metastasis, and the distribution patterns of lymph node metastases. In particular, we set out to evaluate the specific LSNs, which are difficult to resect on segmentectomy (isolated LSNs [iLSNs]). RESULTS: Of all patients, 34 (11%) had lymph node metastases (pN1: 9, pN2: 25). The median tumor sizes and tumor disappearance rates (TDRs) on TSCT were significantly larger and lower, respectively, compared with those of the remaining 273 node-negative patients. All 34 node-positive patients had a solid-dominant component on TSCT (TDR < 0.25). Of these, nine patients (n = 5, station 11, n = 4, station 13) were iLSN positive, but all of them also had metastases to station 12 or mediastinal lymph nodes. No patients had solitary metastasis in iLSNs. CONCLUSIONS: The reasonable extent of dissection for intentional segmentectomy for small (≤ 2 cm) peripheral NSCLC includes LSNs in the segments with tumors, and the hilar and mediastinal nodes. It may not be necessary to examine iLSNs. Systematic lymph node dissection might not be necessary for tumors with ground grass opacity on TSCT (TDR ≥ 0.25).