Five papers showed a lower N1 nodal upstaging with video-assisted thoracic surgery (VATS) compared to open surgery in patients with cStage-I NSCLC . This finding questions the oncologic quality of minimal invasive lung cancer surgery, especially the quality of hilar and intrapulmonary lymh node dissection. However, these retrospective studies did not include analysis of central tumor location, although central tumors have a reported higher chance of N1 upstaging . Possibly, this creates a selection bias as surgeons might select central lesions deliberately for open surgery in line with initial VATS feasibility reports

After optimal preoperative staging, 10 to 25% of patients with clinical stage I (cStage-I) non-small cell lung cancer (NSCLC) are found to have unforeseen positive lymph nodes during resection.

Central tumors, even if they are smaller than 3cm (cT1), have a higher incidence of both intrapulmonary or hilar (N1) or ipsilateral mediastinal (N2) lymph node involvement in comparison to peripheral lesions.

In a cohort of patients that underwent identical preoperative mediastinal evaluation and postoperative pathologic tissue examination of equal quality, nodal upstaging can be used as a quality indicator of oncologic thoracic surgery. Or, it can be used as an instrument to compare different techniques, such as thoracoscopic (VATS) versus open lung resections for lung cancer.

Five papers showed a lower N1 nodal upstaging with video-assisted thoracic surgery (VATS) compared to open surgery. These retrospective studies did not include tumor location.

The investigators hypothesize that this creates a bias as surgeons might have chosen an open approach when the tumor was centrally located. This is in line with initial feasibility reports and guidelines that excluded patients with central lesions. This results in a higher prevalence of positive N1 nodes in patients operated with the open approach.

Our single centre analysis showed a one in three chance of nodal upstaging in central located cStage-I tumors , multivariate analysis showed central location to be the only significant predictor for upstaging, and not the surgical technique.

The aim of this multicentric study is to investigate risk factors for nodal upstaging, including tumor location, in patients with cStage-I NSCLC and validate previous findings.

Inclusion Criteria:

• Patients operated in 2014
• NSCLC on final pathology
• cStage-I (cT1-2a cN0 cM0 ) before start of incision for anatomical resection.
• This includes: open/VATS/ Robotic Assisted Thoracoscopic Surgery (RATS)
• This includes: lobectomy, bilobectomy, sleeve or pneumonectomy (not wedge)

Exclusion Criteria:

• Higher clinical stage than cStage-I
• Former therapy for lung cancer (chemotherapy, radiotherapy, surgery)
• Metastatic disease
• Induction chemo- or radiotherapy
• Non-anatomical resections (wedge)
• Previous lymph node disease
• No positron emission tomography (PET) or Missing PET report

Per centre, a list of consecutive patients operated for cStage-I NSCLC in 2014 is selected.

cStage-I is decided based on all information before resection is started in accordance to the 7th edition of TNM