Number of mediastinal lymph nodes in non-small cell lung cancer: a Gaussian curve, not a prognostic factor.

BACKGROUND: It has been proposed that examining a greater number of lymph nodes (LNs) in patients with non-small-cell lung cancer (NSCLC) treated by surgical resection may increase the likelihood of proper staging and affect outcome. Our purpose was to evaluate the interindividual variability and prognostic relevance of the number of LNs harvested during complete pulmonary and mediastinal lymphadenectomy performed for NSCLC.

METHODS: We prospectively collected and retrospectively reviewed the data from 1,095 patients who underwent lung cancer resection in association with systematic lymphadenectomy and pulmonary and mediastinal LN counts from 2004 to 2009. We analyzed the interindividual variability and prognostic impact of the number of LNs on overall survival (OS).

RESULTS: The mean number of harvested pulmonary and mediastinal LNs was 17.4±7.3 (range, 1-65) and was higher in male patients, right lung surgical procedures, lobectomy and pneumonectomy, N2 disease, and pIII stage. The mean number of harvested mediastinal LNs was 10.7±5.6 and was normally distributed (range, 0-49; median, 10). The 5-year survival rate was 53.8%. Overall survival was influenced by the number of involved stations (single-station versus multi-station disease, 5-year survival rates 31.5% versus 16.9%, respectively; p=0.041) but not by the number of harvested LNs, the number of harvested mediastinal LNs, or the number of positive mediastinal LNs.

CONCLUSIONS: After lung cancer resection and complete lymphadenectomy, the number of LNs is subject to normally distributed interindividual variability, with no significant impact on OS. Recommending an optimal number of nodes is therefore arbitrary. Instead, our recommendation is to perform a complete systematic pulmonary and mediastinal lymphadenectomy following established anatomical boundaries.