Modification of N staging systems for penile cancer: a more precise prediction of prognosis

BACKGROUND: The tumour-node-metastasis (TNM) classification is the most widely used tool for penile cancer. However, the current system is based on few studies and has been unchanged since 2009. We determined whether a modified pathological N staging system that incorporates the laterality and number of lymph node metastases (LNMs) increases the accuracy of the results in predicting survival compared with the 7th edition of the pathological N staging system of the American Joint Committee on Cancer (AJCC) for penile cancer. METHODS: The clinical and histopathologic data from 111 patients with penile cancer with LNMs were analysed. Univariate and multivariate Cox proportional hazard regression analyses were used to determine the impact of the clinical and pathological factors on disease-specific survival of these patients. The predictive accuracy was further assessed using the concordance index. RESULTS: According to the 7th edition of the pathological N classification, the 3-year disease-specific survival (DSS) rates for patients with pN1, pN2, and pN3 disease are 89.6%, 65.9%, and 33.6%, respectively (P(N1–N2)=0.030, P(N2–N3)<0.001, P<0.001). Under the modified pathological N category criteria, the 3-year DSS rates for pN1, pN2, and pN3 patients were 90.7%, 60.5%, and 31.4%, respectively (P(N1–N2)=0.005, P(N2–N3)=0.004, P<0.001). In separate multivariate Cox regression models, only modified N stages (hazard ratio: 4.877, 10.895; P=0.018, P<0.001) exhibited independent effects on the outcome. The accuracy of the modified pathological N category was significantly increased. CONCLUSIONS: The modified pathological N staging system is a better reflection of the prognosis of patients with penile cancer. Our study should contribute to the improvement of prognostic stratification and systemic treatment to avoid overtreatment of patients.