Methods: Between April 2003 and August 2017, a total of 105 patients (99 males, 6 females; mean age: 54.5±8.2 years; range, 27 to 73 years) who were diagnosed with pathologically proven Stage 3A-B N2 non-small cell lung cancer and received neoadjuvant therapy and subsequently lung resection were retrospectively analyzed. Staging algorithm groups (Group 1=first mediastinoscopy-second clinic, Group 2=first mediastinoscopy-second minimally invasive, Group 3=first mediastinoscopy-second re-mediastinoscopy, and Group 4=first minimally invasive-second mediastinoscopy) were created and compared.

Results: In the first stage, N2 diagnosis was made in 90 patients by mediastinoscopy and in 15 patients by minimally invasive method. In the second stage, 44 patients were restaged by the clinical method, 23 by the minimally invasive method, 23 by re-mediastinoscopy, and 15 by mediastinoscopy. The false negativity rates of Groups 1, 2, 3, and 4 were 27.2%, 26.1%, 21.8%, and 13.3%, respectively. The most reliable staging algorithm was found to be the minimally invasive method in the first step and mediastinoscopy in the second step. The mean overall five-year survival rate was 46.3±4.4%, and downstaging in lymph node involvement was found to have a favorable effect on survival (54.3% vs. 21.8%, respectively; p=0.003).

Conclusion: The staging method to be chosen before and after neoadjuvant therapy is critical in the treatment of Stage 3A-B N2 non-small cell lung cancer. In re-mediastinoscopy, the rate of false negativity increases due to technical difficulties and insufficient sampling. As the most optimal staging algorithm, the minimally invasive method is recommended in the first step and mediastinoscopy in the second step.