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.