Evaluation of multiple recurrence events in superficial bladder cancer patients treated with intravesical bacillus Calmette-Guérin therapy using the Andersen-Gill's model.

To evaluate factors affecting recurrence after intravesical bacillus Calmette-Guérin (BCG) therapy (Tokyo 172 strain), we reviewed data for 101 patients with superficial bladder cancer (pTa [n = 80] and pT1 [n = 21]) treated between 1985 and 1999. The median follow-up period was 58.9 months. Factors affecting the first tumour recurrence were evaluated using Cox's proportional hazards model and those affecting multiple recurrence with Andersen-Gill's model. The 5-year recurrence-free rate was 63% for all 101 patients. The recurrence frequency, defined as times per 100 patient-months of follow-up, greatly decreased from 7.3 +/- 9.6 (SD) before the instillation to 2.6 +/- 5.6 after the therapy (p < 0.0001). Patients with pT1 tumours tended to have earlier recurrence than those with pTa tumours (p = 0.06). Multivariate analysis using Cox's proportional hazards model revealed that a history of bladder cancer and pathological stage were independent factors affecting the first tumour recurrence after the BCG therapy. When multiple endpoints of recurrence were evaluated using the Andersen-Gill's model, number of tumours as well as a history of bladder cancer and pathological stage demonstrated significant links to tumour recurrence after the BCG therapy. The 5-year progression-free and 5-year survival rates were 89.3% and 85.3% for all the 101 patients, respectively. Because intravesical recurrence may involve multiple events during the clinical course of patients with bladder cancer, the Andersen-Gill's model appears useful for evaluation of risk factors.