An assessment of the possible association of isoniazid with human cancer deaths.

The data from 2 U. S. Public Health Service trials of isoniazid preventive therapy were reviewed in an effort to evaluate the risk of death from cancer among persons who received such therapy. Each of these prospective trials used random assignment to either isoniazid or placebo. More than 25,000 persons participated in each of the trials. The length of follow-up ranged from 10 to 14 years in one trial and from 9 to 11 years in the other. No significant difference in the incidence of death from cancer was noted between groups treated with placebo or with isoniazid in either of the studies. This was true even when deaths due to specific types of cancer and age-specific cancer death rates were compared. These data do not support a carcinogenic effect of isoniazid in humans.