Impact of age on outcomes of patients with non-muscle-invasive bladder cancer treated with immediate postoperative instillation of mitomycin C

Objectives: To evaluate whether age affects the clinical benefit afforded by immediate postoperative intravesical instillation of mitomycin C in a contemporary cohort of patients with NMIBC. Patients and methods: A total of 4,258 patients with NMIBC treated with transurethral resection of the bladder with (n = 2,605, 61%) or without (n = 1,652, 39%) one immediate instillation of mitomycin C from 5 institutions (study period: 2000-2007) were included. No patients received adjuvant instillations. A multivariable Cox proportional hazards regression model adjusting for standard clinical and pathological features tested the potential interaction term between age and administration of mitomycin C with regard to disease recurrence. Results: A total of 2,063 patients experienced disease recurrence with a median follow-up of 48 months for those who did not recur. In multivariable Cox regression analysis, immediate postoperative instillation of mitomycin C (HR: 0.62; 95% CI: 0.56-0.68; P<0.0001) and age (HR: 1.04; 95% CI: 1.00-1.09; P = 0.036) were associated with disease recurrence. We observed only slight decreases in recurrence-free survival with age irrespective of treatment administration of mitomycin C or not. Conclusion: We confirmed reduced disease recurrence rates associated with 1 immediate postoperative intravesical instillation of mitomycin C in NMIBC patients. The benefit on recurrence-free survival of a postoperative intravesical instillation was preserved across all ages and therefore age by itself should not be taken into consideration when deciding to use it.