Relationship between lymph node ratio and cancer-specific survival in a contemporary series of patients with penile cancer and lymph node metastases.

OBJECTIVE: To evaluate the association between lymph node ratio (LNR) and cancer-specific survival (CSS) in a population of patients with penile cancer and lymph node metastases (LNM).

PATIENTS AND METHODS: We evaluated 81 patients with pathologically determined LNM who were surgically treated at our institution between 2000 and 2012. We considered LNR both as a continuously coded and as a categorically coded variable. The minimum-P-value approach was used to determine the most significant LNR threshold. The Kaplan-Meier method was used to determine CSS rates, and univariable and multivariable Cox regression models were fitted to test the predictors of CSS.

RESULTS: The median (interquartile range [IQR]) numbers of positive and removed lymph nodes were 2 (1-4) and 22 (13-30), respectively. The median (IQR) LNR was 10.3 (6.3-16.6)% and the most significant LNR threshold was 22%. The median (IQR) follow-up was 26 (16-62) months. Overall, the 5-year CSS rate was 50.5%. After stratification according to LNR, 5-year CSS rates were 65.2% vs 9.6% in patients with LNR < 22% vs LNR ≥ 22%, respectively (P < 0.001). In multivariable Cox regression models, after adjusting for several established prognostic factors, LNR was as independent predictor of CSS (P≤0.012). Finally, LNR significantly improved the accuracy of multivariable Cox regression models by 4.9-10.5%.

CONCLUSIONS: Although further investigations are needed to evaluate the relationship between tumour burden and treatment intensity, LNR may represent a powerful predictor of CSS in patients with penile cancer and pathologically determined LNM.