Increased lymph node ratio predicts poor survival in pediatric rhabdomyosarcoma

Abstract

Background/Purpose: Lymph Node Ratio (LNR) is defined as the number of positive lymph nodes (pLN) divided by total lymph nodes (LN) examined. LNR correlates with recurrence and/or overall survival in many adult cancers but has not previously been described in pediatric oncologic disease. We hypothesized that LNR correlates with worse disease specific survival (DSS) in pediatric rhabdomyosarcoma (RMS). Methods: Patients < 20 years who underwent surgery for RMS between 1988 and 2013 in the SEER database were analyzed. Results: 188 patients with a mean age at diagnosis of 8.8 ± 6 years and a mean LNR of 0.13 ± 0.27 were identified. Univariate analysis found that alveolar type, positive lymph node (pLN), stage, site, LNR, and age had significantly worse survival. Cox regression analysis identified LNR > 0.75 (HR 4.32, P = 0.015), alveolar histology (HR 4.797, P < 0.003), age < 1 year (HR 4.402, P = 0.004), and distant disease (HR 5.738, P < 0.001), as independent determinants of worse DSS. pLN and site were not statistically significant determinant of DSS on multivariate analysis. DSS for the entire cohort was 83% at 5 and 78% at 10 and 15 years. DSS at 5, 10, and 15 year for LNR ≤ 0.75 was 79% while patients with LNR > 0.75 had a 22% 5 year and 0% 10 year survival (P < 0.001). Conclusions: LNR is superior to pLN status as an independent prognostic indicator of DSS in pediatric RMS. Level of Evidence: Level III.