Prognostic value of L4 lymph node dissection during video-assisted thoracoscopic surgery in patients with left-sided non-small cell lung cancer: a single-center, retrospective cohort study.

Background: Lymph node dissection (LND) is crucial procedure during radical resection of non-small cell lung cancer (NSCLC), but the prognostic value of L4 LND remains elusive. To investigate the prognostic value of L4 LND in patients with left-side NSCLC who underwent video-assisted thoracoscopic surgery (VATS).

Methods: Three hundred twelve patients who underwent VATS between Jan. 2007 and Dec. 2016 were reviewed. Of those, 119 underwent L4 LND (L4), whereas the other 193 patients did not (L4). The inclusion criteria were as follows: patients diagnosed with primary left-sided NSCLC who underwent VATS lobectomy combined with LND; patients subjected to R0 resection and tumor pathological stage TNM0. The primary endpoint was overall survival (OS). OS was calculated from the operation date to the date of death. The chi-square test was used for categorical variables, and a t test was used for continuous variables.

Results: A total of 119 patients underwent L4 LND, and the procedure was more likely to be performed on upper lobe tumors (P=0.019). Patient distributions with respect to age, gender, smoking history, clinical stage, adjuvant therapy, tumor differentiation and tumor size were well balanced between two groups. More lymph nodes (LNs) were dissected in the L4 group than in the L4 group (P<0.001). The rate of metastasis to L4 lymph nodes was 9.2%, which was comparable between patients with upper and lower lobe tumors (8.9% 10.0%, P=1.000). The L4 group exhibited a significantly better OS than the L4 group (median OS: undefined 130 months, HR 0.47; 95% CI: 0.31-0.72; P=0.002). Multivariate analysis showed that L4 LND was an independent factor for OS. However, OS did not significantly differ between the two groups of cT1aN0 and cT1bN0 patients (OS: HR 0.44; 95% CI: 0.18-1.06; P=0.12).

Conclusions: L4 LND is recommended for patients with left-sided NSCLC as an essential component of radical resection. The role of L4 LND in cT1a-bN0 disease warrants further study.