Proposal for reclassification of N staging system in penile cancer patients, based on number of positive lymph nodes

In the present study, we aim to compare the rationality of proposed N classification based on the number of metastatic lymph nodes (LNs) with the current one. A total of 509 penile cancer patients at our institute were analyzed. Univariable and multivariable statistical analyses were used to assess cancer-specific survival (CSS) in 2 staging systems. Harrell's concordance index was applied to evaluate predictive accuracy of the current and proposed N classification in predicting CSS. We propose a new classification: pN1 (metastasis in 1-2 regional LNs), pN2 (metastasis in 3 regional LNs, or 3 or fewer regional lymph nodes with extranodal extension), and pN3 (metastasis in 4 or more regional LNs). According to the current and proposed N classification, the 5-year CSS of penile cancer patients with pN1, pN2 and pN3 was 85.8%, 39.0%, and 19.7%; and with pN1, pN2 and pN3 was 79.8%, 39.3% and 15.3%, which almost all showed significant difference (P < .001, P = .259) (P < .001, P < .001). Multivariable predictive accuracy of the proposed and current N staging was 76.48% and 70.92% (5.56% gain; P < .001). With a multivariable model of clinical features, both current (hazard ratio [HR], 7.761, 10.612; P < .001, P < .001) and proposed N stages (HR, 3.792, 3.971; P < .001, P < .001) exhibited independent effects on survival. The proposed N classification is superior to the current one, which is simpler and provides more accurate prognosis.