Lobe-Specific Lymph Node Dissection for Clinical Early-Stage (cIA) Peripheral Non-small Cell Lung Cancer Patients: What and How?

Objective We investigated the possible lobe-specific lymph node (LN) metastasis pattern of early-stage peripheral non-small cell lung cancers (NSCLC) and define the extent of lobe-specific LN dissection for them. Methods We retrospectively collected clinical data of patients undergoing lobectomy or segmentectomy with systematic lymphadenectomy for clinical T1N0M0 peripheral NSCLC from January 2015 to December 2018. The LN metastasis pattern was analyzed by tumor lobe location. Results A total of 590 patients were included for analysis. The mean number of total dissected LNs was 12.3 +/- 5.8 and 8.2 +/- 4.1 for total dissected mediastinal LNs. The rate of mediastinal LN metastasis was 9.5%. For cases of upper lobe tumor and lower lobe tumor, 8.8% and 6.0% of them respectively metastasized to the upper LN zone (P = 0.274). However, upper lobe tumors hardly metastasized to the subcarinal (0.3%) and lower (0.3%) LN zones while for lower lobe tumors, the rate of LN metastasis was 10.2% and 5.4% respectively (both P < 0.001). However, all cases (100%) metastasizing from lower lobes to the upper LN zone had a tumor size of 2-3 cm, whereas cases with a tumor size <= 2 cm had no metastasis (0%). None of the tumors in the right middle lobe metastasized to the lower LN zone (0%). Conclusions A lobe-specific LN metastasis pattern was observed in clinical stage IA peripheral NSCLC. For tumors in upper lobes (<= 3 cm), there may be no need to dissect lower mediastinal LNs and for tumors in lower lobes (<= 2 cm), dissecting upper mediastinal LNs may not be required.