Improving the Efficacy of BCG Immunotherapy by Dose Reduction

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Abstract
Several clinical trials have shown intravesical bacillus Calmette-Guérin (BCG) to be effective in the prophylaxis of papillary tumour recurrences and in the therapy of bladder carcinoma in situ (CIS), as well as in delaying progression to muscle invasion. Nevertheless, the optimal regimen of BCG therapy for superficial bladder cancer has still to be defined. In a previous phase II trial, a low-dose regimen (BCG Pasteur strain, 75 mg) was able to achieve clinically significant response rates with a decrease in side-effects compared with other reported studies using standard-dose BCG. However, a phase III randomized trial - low dose versus standard dose (BCG Pasteur strain, 75 vs. 150 mg) - was considered necessary to clarify definitively the relationships between dose, efficacy and toxicity. The results of the interim analysis of 183 patients (performed in 1993) have shown response rates to be better in patients submitted to a low-dose BCG regimen (p = 0.0009) and a significant decrease in most of the common side-effects (cystitis, fever, haematuria; p < 0.05). Breaking down the results by stage, no differences in response rates were found in patients with stage TaM (70 vs. 62% in low-dose and standard-dose regimens, respectively, p = 0.5). In TIM and CIS stages, 82 and 0 (p = 0.07), and 64 and 0% (p = 0.0003) of patients were free of tumour following low-dose and standard-dose therapy, respectively. An additional 6-week course in patients who failed the induction course retrieved additional responses in both groups. No differences in progression rates were observed. In conclusion, a low-dose regimen gives superior protection from recurrences with a decrease in side-effects; an additional 6-week course can achieve further complete responses in patients who failed the induction course.

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