Lobe-Specific nodal dissection for clinical stage I and II NSCLC: Japanese Multi-Institutional retrospective study using a propensity score analysis

Objectives: The purpose of this study was to assess the surgical outcomes according to the extent of mediastinal lymph node dissection for patients with NSCLC by using a nationwide registry database. Methods: From among 11,663 patients in a Japanese lung cancer registry study for 2004, 5392 patients with clinical stage (c-stage) I or II NSCLC that was completely resected by lobectomy and either systematic (SND) or lobe-specific nodal dissection (LSD) were enrolled. Patients who received preoperative therapy or had middle lobe tumor were excluded. In the LSD group, inferior mediastinal (subcarinal) nodes were not dissected for upper lobe tumors, and superior mediastinal nodes were not dissected for lower lobe tumors. To reduce the selection bias, an inverse probability of treatment weighting method using a propensity score was implemented. Results: LSD and SND were performed in 1268 patients (23.5%) and 4124 patients (76.5%), respectively. The LSD group included more upper lobe and c-stage I tumors and less pathological N2 disease than the SND group. Extended pathological N2 disease outside LSD area was found in 3.2% of the SND group. The 5-year overall survival was 81.5% in the LSD group and 75.9% in the SND group. An inverse probability of treatment weighting-Adjusted Cox model showed that LSD did not have a negative prognostic impact and instead was associated with favorable survival (hazard ratio = 0.68, 95% confidence interval: 0.60=0.77). Conclusions: This retrospective registry study suggested that LSD is an alternative to SND for selected patients with c-stage I or II NSCLC. Future prospective studies are warranted to determine whether LSD is applicable and provides clinical benefit for the general population of patients with cstage I or II NSCLC.