The effect of isoniazid on BCG-induced toxicity in patients with superficial bladder cancer

The use of bacillus Calmette-Guerin in the treatment of transitional cell c ancer of the bladder has caused concern because of its associated adverse e ffects. We conducted a randomized prospective, double-blind, multicentre st udy to determine whether isoniazid prophylaxis could reduce BCG-induced tox icity without compromising its immunotherapeutic effects. Patients (n = 160 ) with histologically documented urothelial cancer (pTa-T1, pTis, G1-3) wer e treated with 6 weekly instillations of BCG Connaught strain, 81 mg, admin istered concomitantly with a 3-day course of isoniazid (300 mg o.d.) or pla cebo. Side-effects were recorded with each treatment and at follow-up. Of t he patients treated with isoniazid, 19% remained free from side-effects, co mpared with 46% of the placebo group. Local side-effects confined to the bl adder were significantly lower among those receiving isoniazid (35% vs. 48% , p < 0.01). Local side-effects together with systemic adverse effects such as fever, nausea or skin rash were experienced by 30% of patients in each arm. There were no differences in tumour recurrence between the two patient groups. Concomitant isoniazid reduces the local, but not the systemic side -effects of topically applied BCG without compromising the antitumour effec t on superficial, transitional cell cancer of the bladder during a follow-u p period that now exceeds 2 years. Copyright (C) 2000 S. Karger AG, Basel.