D. T. Nguyen2, J. P. Fontaine1,2, L. Robinson1,2, R. Keenan1,2, E. Toloza1,2 1Moffitt Cancer Center,Department Of Thoracic Oncology,Tampa, FL, USA 2University Of South Florida Health Morsani College Of Medicine,Tampa, FL, USA
Introduction: Stage-2 nonsmall-cell lung cancers (NSCLC) include T1N1M0 and T2N1M0 tumors in the current Tumor-Nodal-Metastases (TNM) classification and are usually treated surgically with lymph node (LN) dissection and adjuvant chemotherapy. Multiple studies report that a high lymph node ratio (LNR), which is the number of positive LNs divided by total LNs resected, as a negative prognostic factor in NSCLC patients with N1 disease who underwent surgical resection with postoperative radiation therapy (PORT). We sought to determine if a higher LNR predicts worse survival after lobectomy or pneumonectomy in NSCLC patients (pts) with N1 disease but who never received PORT.
Methods: Using Surveillance, Epidemiology, and End Results (SEER) data, we identified pts who underwent lobectomy or pneumonectomy with LN excision (LNE) for T1N1 or T2N1 NSCLC from 1988-2013. We excluded pts who had radiation therapy, multiple primary NSCLC tumors, or zero to unknown number of LNs resected. We included pts with Adenocarcinoma (AD), Squamous Cell (SQ), Neuroendocrine (NE), or Adenosquamous (AS) histology. Log-rank test was used to compare Kaplan-Meier survival of pts who had LNR <0.125 vs. 0.125-0.5 vs. >0.5, stratified by surgical type and histology.
Results: Of 3,452 pts, 2666 (77.2%) had lobectomy and 786 (22.8%) had pneumonectomy. There were 1935 AD pts (56.1%), 1308 SQ pts (37.9%), 67 NE pts (1.9%), and 141 AS pts (4.1%). When comparing all 3 LNR groups for the entire cohort, 1082 pts (31.3%) had LNR <0.125, 1758 pts (50.9%) had LNR 0.125-0.5, and 612 pts (17.7%) had LNR >0.5. There were no significant differences in 5-yr survival among all 3 LNR groups for the entire population (p=0.551). After lobectomy, 854 pts (32.0%) had LNR <0.125, 1357 (50.9%) pts had LNR 0.125-0.50, and 455 pts (17.1%) had LNR >0.5. After pneumonectomy, 228 pts (29.0%) had LNR <0.125, 401 pts (51.0%) had LNR 0.125-0.5, and 157 pts (19.9%) had LNR >0.5. There was no significant difference in 5-yr survival among all 3 LNR groups in either lobectomy pts (p=0.576) or pneumonectomy pts (p=0.212). When stratified by histology, we did not find any significance in 5-yr survival among all 3 LNR groups in AD pts (p=0.284), SQ pts (p=0.908), NE pts (p=0.065), or AS pts (p=0.662). There were no differences in 5-yr survival between lobectomy vs. pneumonectomy pts at LNR <0.125 (p=0.945), at LNR 0.125-0.5 (p=0.066), or at LNR >0.5(p=0.39).
Conclusion: Patients with lower LNR did not have better survival than those with higher LNR in either lobectomy or pneumonectomy pts. Lower LNR also did not predict better survival in each histology subgroup. These findings question the prognostic value of LNRs in NSCLC patients with N1 disease after lobectomy or pneumonectomy without PORT and suggest further evaluation of LNRs as a prognostic factor.