Does the extent of lymph node dissection influence outcome in patients with stage I non-small-cell lung cancer?

Objective: To assess the therapeutic effect of the extent of lymph node dissection performed in patients with a stage pI non-small-cell lung cancer (NSCLC). Methods: We analysed data on 465 patients with stage I NSCLC who were treated with surgical resection and some form of lymph node sampling. The median number of lymph node sampled was 10 and the median number of ipsilateral mediastinal lymph node stations sampled was two. We chose to define a procedure that harvested 10 or more lymph nodes and sampled two or more ipsilateral mediastinal stations as a lymphadenectomy, by contrast with sampling when one or both criteria were not satisfied. The effect of the surgical techniques: lymph node sampling (LS; n=207) vs. lymphadenectomy (LA; n=258) on 30-day mortality and overall survival were investigated. Results: A total of 6244 lymph nodes was examined, including 4306 mediastinal lymph nodes. The mean (±SD) numbers of removed lymph nodes were 7±6.1 per patient following LS vs.18.6±9.3 following LA (P=0.001). An average mean of 1±0.90 mediastinal lymph node station per patient was sampled following LS vs. 2.7±0.8 following LA (P<10^-6). Overall 30-day mortality rates were 2.4 and 3.1%, respectively. LA was disclosed as a favourable prognosticator at multivariate analysis (Hazard Risk: 1.43; 95% Confidence Interval: 1.00-2.04; P=0.048), together with younger patient age, absence of blood vessels invasion, and smaller tumour size. Conclusions: Importance of lymph node dissection affects patients outcome, while it does not enhance the operative mortality. A minimum of 10 lymph nodes assessed, and two mediastinal stations sampled are suggested as possible pragmatic markers of the quality of lymphadenectomy.