Adherence to the mediastinal staging guideline and unforeseen N2 disease in patients with resectable non-small cell lung cancer: Nationwide results from the Dutch Lung Cancer Audit - Surgery

•Adherence to the European guideline on mediastinal lymph node staging in NSCLC was poor.•uN2 rates were comparable in patients who were staged conform the guideline or not•Highest uN2 rate was found in patients with cN1-3 as indication for staging.•Strict guideline adherence affected the uN2 rate in the subgroup with cN1-3 only.•Direct surgical resection in patients without an indication for staging seems appropriate. Invasive mediastinal staging is advised by guidelines in patients with resectable non-small cell lung cancer (NSCLC) and suspicious lymph nodes (cN1-3) or for central, FDG-non-avid or peripheral tumours >3 cm. Our objective was to assess current guideline adherence and consequent unforeseen N2 disease (uN2) in NSCLC patients having various indications for mediastinal staging. We analysed the Dutch Lung Cancer Audit – Surgery data of all patients who underwent a primary lung resection with lymph node dissection for NSCLC in 2017-2018. Based on the 2015 ESTS-ERS-ESGE guideline we assessed the use of initial endosonography and confirmatory mediastinoscopy as well as uN2 rates. A total of 2238 patients were analysed. 43 % (95 %-CI: 41–45) underwent initial endosonography followed by a confirmatory mediastinoscopy in 44 % (95 %-CI:40–47) of them, resulting in a 19 % (95 %-CI: 17–20) rate of properly staged patient according to the guidelines. uN2 was demonstrated in 12.5 % (95 %-CI: 9.7–16.0) of correctly staged patients compared to 10.9 % (95 %-CI: 9.6–12.4) who were not (p = .36). The highest uN2 rate was found in cN1-3 patients who were not staged (23.0 %, 95 %-CI: 16.4–31.2) compared to 13.0 % (95 %-CI: 9.7–17.1) who were (p = .01). Guideline adherence in Dutch NSCLC patients with an indication for invasive mediastinal staging is poor. The highest uN2 rate was found in unstaged cN1-3 patients, suggesting that this subgroup may benefit from an appropriate staging conform guidelines.