The Relationship Between Nodal Metastases and Primary Location in Stage I Non-Small Cell Lung Cancer

This study examines the relationship between location of the primary tumor and specific nodal metastases in clinical stage 1 non-small cell lung cancer (NSCLC) patients undergoing lobectomy.

We retrospectively analyzed all lobectomies performed at a single institution, between January 2005 and December 2019, for clinical stage I NSCLC patients. Patients selected for this study were clinically node negative (cN0) by positron emission tomography-computed tomography scan and selectively by endobronchial ultrasound or mediastinoscopy. Cases of postoperative pathologic nodal upstaging were identified among these patients. For each patient upstaged, the specific lymph node stations found to be positive were recorded. Descriptive statistics, chi-squared tests, and Fisher's exact test were utilized to identify independent risk factors for upstaging to specific N1 and N2 lymph node stations. All clinical and pathologic staging information was retrospectively normalized to the International Association for the Study of Lung Cancer 8th Edition TNM Classification.

The research cohort included 645 patients. The mean age was 68 years (standard deviation ± 9.2), 54% were female, and 88% were White, 11% Black, and 1% other. Twelve percent (n = 75) were upstaged from cN0 to pN1 or pN2 upon final pathologic examination: 41 to pN1 (54.7%) and 34 to pN2 (45.3%). The primary tumor location with the highest rate of nodal upstaging was the left upper lobe (LUL) (12.8%). Tumors in the right middle lobe had the lowest rate of unsuspected nodal metastases (8.8%). Out of all upstaged patients, there were no positive level eight lymph nodes, and only 1 patient with a positive level nine lymph node. Lymph node levels five and six were only positive in LUL primary tumors, a relationship that approached statistical significance (P = 0.0797). No patients with a LUL primary tumor had a positive level seven lymph node. Upstaging at station 12 was significantly associated with the location of the primary tumor, occurring less often in tumors originating in the right upper lobe in comparison to other lobes (P = 0.0288).

We identified relationships between the location of a primary tumor and specific nodal upstaging in patients with clinical stage I NSCLC who undergo lobectomy. We found the following: 1) only 1 patient had a positive level eight or nine lymph node out of 645 patients; 2) only LUL primary tumors demonstrated upstaging to level five or six lymph nodes; and 3) right upper lobe tumors were significantly less likely to be associated with a positive level 12 lymph node.