Extracapsular extension of pN2 lymph node metastases is not prognostically significant in surgically resected patients with non-small cell lung cancer.

Objectives: In patients with non-small cell lung cancer (NSCLC) the pathologic lymph node status N2 is a heterogeneous entity, with different degrees of lymph node involvement representing different prognoses. It is speculated whether extra capsular nodal extension may help to define a subgroup with implications on long-term survival.

Methods: We retrospectively identified 118 patients with non-small cell lung cancer (65 men, 53 women), who were treated between 2013 and 2018 and found to have pathologic N2 lymph node involvement. In all patients lung resection with systematic mediastinal and hilar lymph node dissection was performed with curative intent. In N2 lymph node metastases capsules of affected lymph nodes were examined microscopically as to whether extracapsular extension was present.

Results: 51 patients (43 %) had extracapsular extension (ENE). Most of these patients (n=35) only had ENE in a single lymph node (69 %). The overall 5-year survival rate was 24.6 % and progression-free survival rate 17.8 %. In the multivariate analysis OS was worse for patients with multiple affected pN2 stations, concurrent N1 metastases, increasing age, and larger tumor size. For the percentage of lymph nodes affected with ENE (of total examined) only a non-significant trend towards worse OS could be observed (p=0.06).

Conclusions: Although we could not demonstrate significant prognostic differences between N2 extra capsular nodal involvement within our patient population, other analyses may yield different results. However, clinicians should continue performing thorough lymph nodes dissections in order to achieve local complete resection even in patients with extra capsular tumor spread.