Development and external validation of a prognostic tool for prediction of cancer‐specific mortality after complete loco‐regional pathological staging for squamous cell carcinoma of the penis

OBJECTIVE: To develop a novel postoperative prognostic tool, which attempts to integrate both pathological tumour stage and histopathological factors, for prediction of cancer-specific mortality (CSM) of squamous cell carcinoma of the penis (SCCP). PATIENTS AND METHODS: Patients with SCCP treated with inguinal lymph node dissection (ILND) or sentinel LN biopsy at a single institution were used for nomogram development and internal validation (n = 434), while a second cohort was used for external validation (n = 338). Multivariable Cox proportional hazards were used to examine the prognostic ability of patient age, a modified tumour staging that distinguishes between spongiosum and cavernosum body ingrowth tumours, a modified LN staging that integrates information on presence/absence of LN metastasis, extent of inguinal LN metastases, pelvic LN involvement, and extranodal involvement, and tumour grade. Model performance was quantified using measures of discrimination and calibration. RESULTS: Overall, 36% of patients had positive LN metastases (n = 156). In univariable analyses, the modified tumour and LN staging systems were statistically significantly associated with CSM, and remained in the final model with a discrimination of 89% within internal validation, and 95% within external validation. Calibration was nearly perfect. CONCLUSIONS: The newly developed model integrates important prognostic factors, which existing models do not consider. Its performance was highly accurate using measures of discrimination and calibration.