Long-term results of maintenance treatment of mitomycin C or alternating mitomycin C and bacillus Calmette-Guérin instillation therapy of patients with carcinoma in situ of the bladder: a subgroup analysis of the prospective FinnBladder 2 study with a 17-year follow-up.

Objective: Only a few studies with a long-term follow-up exist on patients with carcinoma in situ (CIS) treated with instillation therapy. The objective was to study the long-term outcome of patients with CIS after mitomycin C (MMC) monotherapy or alternating therapy with MMC and bacillus Calmette-Guérin (BCG).

Material and methods: The study population comprised 68 patients with CIS belonging to a larger material of 256 patients with non-muscle-invasive bladder carcinoma who were randomized between 1987 and 1992 in a prospective multicentre study. Patients received the same induction period with MMC and continued with maintenance treatment comprising either monthly instillations of MMC alone or alternating MMC and BCG instillations for up to 2 years. Primary endpoints were cancer-specific and overall mortality. Secondary endpoints were time to first recurrence and time to progression. The principal statistical methods were the Kaplan-Meier method and cumulative incidence analysis.

Results: The overall median follow-up time of the patients with CIS was 7.2 years and the median follow-up time of the patients still alive was 17.1 years. The non-stratified probability of dying from bladder carcinoma at 5, 10 and 15 years was 13%, 25% and 28%, respectively. No significant difference was found between the study groups with respect to time to first recurrence, progression, or disease-specific or overall mortality.

Conclusions: The long-term bladder cancer-specific mortality was unexpectedly low despite the relatively ineffective instillation therapy and the poor outcome of the patients after progression.