The impact on the prognosis of unsuspected N2 disease in non-small-cell lung cancer: indications for thorough mediastinal staging in the modern era

Purpose

Predicting the prognosis of advanced non-small-cell lung cancer (NSCLC) patients who present with clinically unsuspected N2 is very different due to the heterogeneity of this cohort. Thus, this study was undertaken to identify the clinicopathological features and survival of patients with clinical N0 or N1 and pathological N2, namely, unsuspected N2.

Methods

Among 239 patients with pathological N2 NSCLC, we reviewed the cases of 92 (38.5 %) patients who showed unsuspected N2. The prognosis was investigated using the Kaplan–Meier method and a Cox regression model.

Results

The 5-year overall survival (5yOS) of the patients with unsuspected N2 was 51.2 %. Based on a multivariate analysis, age and 18F-fluorodeoxyglucose (FDG) uptake in the lymph nodes were significant prognostic factors of unsuspected N2 (p = 0.0081, 0.0228, respectively). The 5yOS of PET-negative unsuspected N2 (n = 68) was 58.9 %, whereas that of PET-positive unsuspected N2 (n = 24) was 29.7 % (p = 0.0026). Furthermore, the 5yOS of PET-negative unsuspected N2 was significantly better than that of both clinical and pathological N2 s (i.e., suspected N2; n = 60; 5yOS, 42.1 %; p = 0.0051), while no significant difference was observed between PET-positive unsuspected N2 and suspected N2 (p = 0.6325).

Conclusions

A preoperative evaluation of the lymph nodes by PET/CT has a potential benefit in predicting the prognosis. A thorough evaluation of the lymph nodes is, therefore, needed if the lymph nodes show an FDG uptake, even in cases that show a clinical N0 status on thin section CT scans.