Conditional survival of patients with stage I–III squamous cell carcinoma of the penis: temporal changes in cancer-specific mortality

Purpose: To test the conditional survival that examined the effect of event-free survival on cancer-specific mortality after primary tumour excision (PTE) in patients with squamous cell carcinoma of the penis (SCCP). Materials and methods: Within the SEER database (1998–2015), 2282 stage I–III SCCP patients were identified. Conditional survival estimates were used to calculate cancer-specific mortality (CSM) after event-free survival intervals of 1, 2, 3, and 5 years. Multivariable Cox regression models predicted CSM according to event-free survival. Results: After PTE, 5-year CSM-free rate was 78.0% and increased to 84.6%, 88.1%, 92.0%, and 94.2% in patients who survived ≥ 1, ≥ 2, ≥ 3, and ≥ 5 years. After stratification according to tumour characteristics, 5-year CSM-free rates increased from 85.9 to 95.4%, 79.0 to 97.1%, 78.9 to 90.0%, and from 54.5 to 86.0% in those survived ≥ 5 years, respectively, in T1N0, T2N0, T3N0, and N1-2 patients. In multivariable analyses, T2N0 [hazard ratio (HR) 1.68; p value < 0.001], T3N0 (HR 1.94; p value 0.001), and N1-2 (HR 6.61; p value < 0.001) were independent predictors of higher CSM rate at baseline, relative to T1N0. A decrease in all HRs was assessed over time in patients who survived. Attrition due to CSM was highest in N1-2 cohort and lowest in T1N0. Conclusions: Conditional survival models showed a direct relationship between event-free survival duration and subsequent CSM in SCCP patients. Even patients with non-organ-confined disease may achieve survival probabilities similar to those with organ-confined disease after at least 5 years of event-free survival since PTE.