Validation of the prognostic value of lymph node ratio in patients with penile squamous cell carcinoma: a population-based study.

Purpose: The aim of this study was to validate the prognostic value of lymph node ratio (LNR), the proportion of metastatic among removed lymph nodes, for patients with penile squamous cell carcinoma in a population-based database.
Methods: A total of 210 eligible patients with node-positive disease were identified from the surveillance epidemiology end results database. Cancer-specific survival (CSS) was the clinical outcome of interest. The prognostic ability of LNR was assessed by Cox regression analyses. Logrank test was used to compare CSS between low-risk and high-risk groups stratified by cutoff points of LNR.
Results: The median number of LNs removed was 16, and the median value of LNR was 0.20. First, LNR was a significant prognostic factor of CSS in univariate analysis (HR = 4.08). Second, LNR retained independent predictive ability (HR = 6.74) in the multivariate model including demographic data, disease characteristics and number-based LN variables. Addition of LNR remarkably improved the predictive accuracy and clinical usefulness of the survival model. Third, maximum stratification of CSS can be achieved at the cutoff point of 0.33.
Conclusion: In the population-based study, LNR outperformed number-based LN variables for predicting CSS of node-positive penile cancer. The ratio-based prognostic factor stresses the important role of adequate LND and identification of metastatic LNs in the community setting.