Proposal of a Subclassification of pN3 in Squamous Cell Carcinoma of the Penis

To evaluate the differential prognosis of PLNM as compared to ENE and postulate a sub-classification of the pN3 stage of carcinoma penis.

A retrospective analysis of prospectively maintained data of all the patients of penile squamous cell carcinoma operated at our institute between Jan 2016 and May 2023 was conducted. LASSO Cox regression was used to select variables affecting OS. Cox multivariate analysis was performed to derive significant factors which were permuted to form probable sub-classifications. The best sub-classification was selected based on Akaike Information Criteria (AIC) and Kaplan Meier analysis.

Seventy three patients were included in the study. ENE (HR: 2.6, p = 0.038) and PLNM (HR: 3.3, p = 0.004) were significantly associated with OS on Cox multivariate analysis using LASSO based variable selection. Four probable sub-classifications were created of which pN3a (only ENE) and pN3b (only PLNM and ENE+PLNM) showed least AIC (235.065). The mean OS was 36.6 and 17.2 months respectively for pN3a and pN3b subgroups.

ENE had a better OS as compared to PLNM and ENE+PLNM in our study. A sub-classification of pN3 stage of TNM classification is proposed. Multi-institutional prospective studies with large number of patients and longer follow-up should validate our findings.