Clinical impact of number of lymph nodes dissected on postoperative survival in node-negative small cell lung cancer

Objectives: Small cell lung cancer (SCLC) is a lethal histologic subtype of lung cancer. Although the Commission on Cancer recommends pathological examination of at least 10 lymph nodes dissected (LNDs) for resected early-stage non-small cell lung cancer, its survival benefit of LNDs in patients with early-stage SCLC is unknown. Methods: The National Cancer Database was queried for SCLC patients with clinical stage I-II and clinical N0, NX disease per AJCC 7^th edition who had undergone lobectomy between 2004 and 2017. Overall survival of SCLC patients by the number of LNDs was compared using Log-rank tests. Univariate and multivariable Cox proportional hazards analyses were performed. Results: In total, 688 (42%), 311 (20%), 247 (16%), 196 (12%), 126 (8%), and 36 (2%) of 1,584 patients with early-stage SCLC had ≥10, 7-9, 5-6, 3-4, 1-2, and 0 LNDs, respectively. The sequential improvement in the HRs was no longer evident if the number of LNDs exceeds 4. Patients with ≥3 LNDs (n = 1,422) had a significantly longer overall survival than those with <3 LNDs (n = 162) (hazard ratio for death: 0.76, 95% confidence interval: 0.62–0.94, P = 0.0087). Multivariate analysis revealed that ≥3 LNDs was an independent factor for predicting overall survival (hazard ratio for death: 0.76, 95% confidence interval: 0.61–0.93, P = 0.0083). Conclusions: Although we are reluctant to recommend a definitive “optimal number” of LNDs, our findings suggest the prognostic and therapeutic roles for performing ≥3 LNDs in patients with early-stage SCLC who undergo lobectomy.