Patients with primary left lung cancer who underwent 4L lymph node dissection had more favorable survival outcomes than those who did not receive 4L dissection, according a single-center, retrospective study.
“The standard treatment procedure for resectable non-small cell lung cancer involves lobectomy with systemic mediastinal lymph node dissection,” Ya-Nan Wang, PhD, of Tianjin Medical
University Cancer Institute, and colleagues wrote. “However, the degree to which the mediastinal lymph nodes should be exposed and the extent of their excision is still under debate.
“Station 4L LN dissection for left lung cancer is more difficult than that for right lung cancer because of anatomic limitations caused by the aortic arch, left recurrent laryngeal nerve and thoracic duct,” Wang and colleagues added. “Therefore, superior mediastinal lymph node metastasis of left lung cancer is rarely studied.”
However, the International Association for the Study of Lung Cancer (IASLC) suggests that systematic nodal dissection involves the minimal excision of at least three mediastinal nodal stations without requiring 4L lymph nodes among patients with left-sided tumors.
To evaluate the clinical significance of 4L lymph node dissection, Wang and colleagues collected data from 657 patients with primary left lung cancer who underwent surgical pulmonary resection, 139 of whom received 4L lymph node dissection.
Researchers used the lymph node map proposed by IASLC to classify lymph node stations, with the goal of removing station 1 to station 12.
DFS and OS served as the primary endpoints.
Researchers found that 20.9% of patients who underwent 4L lymph node dissection had 4L involvement, which appeared significantly higher than the metastasis rate of station 7 (14%; P = .048) and station 9 (9.8%; P < .001) lymph nodes.
Univariate analysis suggested station 4L metastasis correlated with metastasis in most other lymph node stations except for station 8. However, multivariate analysis showed only station 10 lymph node metastasis served as an independent risk factor for 4L lymph node metastasis (OR = 0.25; 95% CI, 0.1-0.58).
Researchers observed improved 5-year DFS (54.8% vs. 42.7%; P = .0376) and 5-year OS (58.9% vs. 47.2%; P = .02) among patients who underwent 4L lymph node dissection compared with those who did not.
In a multivariate analysis with adjustment for potential confounders, 4L lymph node dissection had an independent benefit on DFS (HR = 1.5; 95% CI, 1.15-1.94) and OS (HR = 1.58; 95% CI, 1.22-2.05).
Propensity score weighting further confirmed patients who underwent 4L lymph node dissection had improved DFS (P = .0014) and OS (P < .001).
The limitations of the study included its retrospective study design, possible selection bias and patients lost to follow-up.
“Consequently, long-term effects remain to be fully confirmed and should be studied further with a larger sample size and a multicenter randomized clinical trial,” the researchers wrote.
In an accompanying editorial, Dirk K.M. De Ruysscher, MD, of the MAASTRO Clinic in the Netherlands and Herbert Decaluwé, MD, of the University Hospitals Leuven in Belgium, agreed a survival benefit is difficult to prove without a randomized controlled trial.
“The findings in the Wang et al study, that surgical removal of station 4L might improve OS, should therefore be viewed as hypothesis generating only,” they wrote. “As the authors note, their study is retrospective with significant known imbalances in the prognostic factors between the group treated with 4L dissection and the other group. Propensity techniques are an attempt to deal with the imbalance of confounders, but they are by no means as strong as randomization.” – by Cassie Homer
Disclosures: The authors report no relevant financial diclosures. De Ruysscher reports institutional consultant/advisory roles with AstraZeneca, Bristol-Myers Squibb, Celgene, Genentech and Merck Serono, and institutional research funding from Bristol-Myers Squibb and Boehringer Ingelheim. Decaluwé reports no relevant financial disclosures.