Is invasive mediastinal staging necessary in intermediate risk patients with negative PET/CT?

Tumor involvement of mediastinal lymph nodes is of high importance in non-small cell lung cancer (NSCLC). Invasive mediastinal staging is recommended in selected patients without evidence of mediastinal involvement on staging by imaging. In the present study we aimed to evaluate the effectiveness of invasive mediastinal staging in reducing pN2, its impact on survival and the risk factors for occult pN2.

Patients with NSCLC tumors larger than 3 cm, central tumors or cN1 cases treated in our institution between 2013 and 2018 were prospectively included in the study. Incidence of pN2 and overall survival was compared among invasively staged (IS) and non-invasively staged groups (NIS). Multivariate analysis was performed to identify risk factors of pN2.

A total of 201 patients were included in the study, 79 (39.3%) of whom were not invasively staged (NIS group) and 122 (60.7%) were invasively staged (IS group). Incidence of cN1 and mean PET/CT uptake was different among both groups. Prevalence of pN2 was similar in both groups (7.6% in NIS vs. 12.6% in IS; P>0.05). Median survival in IS-pN2 patients was 11 months longer than in NIS-pN2 group (33.6 vs. 22.5 months; P=0.245). cN1 emerged as the only a risk factor for pN2.

Invasive staging does not reduce the incidence of pN2. However, this finding could be biased because in our series cN1 patients were more often staged and cN1 has been detected as a risk factor for pN2. In addition patient better selection after invasive staging might have an impact on overall survival. To conclude, invasive mediastinal staging in intermediate risk patients for positive mediastinal nodes is justified.