Presurgical invasive mediastinal staging in lung cancer, unexpected N2 and long-term survival: a registry-based study with data from the Spanish group for video-assisted thoracic surgery.

Background: Mediastinal lymph node staging is a key element in the diagnosis of lung cancer. The combination of computed tomography (CT) and positron emission tomography (PET) has improved staging but some circumstances are known to influence their negative predictive value. The objective of this study was to assess the impact on survival of avoiding invasive mediastinal staging in surgical lung cancer patients with negative mediastinum in CT and PET and intermediate risk of unexpected pN2.

Methods: Data were collected from the prospective cohort of the Spanish Group for Video-Assisted Thoracic Surgery (GEVATS), from December 2016 to March 2018. For this study, patients were selected if they had negative mediastinum in CT and PET findings but tumours >3 cm or located centrally, or with cN1 disease. Patients who did and did not undergo invasive staging [invasive group (IG) and non-invasive group (NIG)] were compared, analysing unexpected pN2 and survival with Kaplan-Meier curves and Cox regression.

Results: A total of 2,826 patients underwent surgery for primary lung cancer. We selected 1,247 patients who had tumours >3 cm, central tumours or cN1. Invasive staging was performed in 275 (22.1%) cases. The unexpected pN2 rate was 9.6% in the NIG and 13.8% in the IG, but half of them were discovered prior to surgery in the IG. Five-year overall survival (OS) was poorer in the IG (52.4% . 64%; P<0.001). In the Cox regression model, male sex, older age, diabetes, synchronous tumour, lower diffusing capacity for carbon monoxide, larger tumour size, higher pathological N-stage, and IG status were significant independent risk factors.

Conclusions: Invasive staging recommended by guidelines could be reduced with an appropriate selection in mediastinal CT- and PET-negative patients with risk factors for unexpected pN2, because rates of pN2 and survival did not worsen without invasive staging.