The possible effect of diazepam on cancer development and growth

Diazepam has the characteristics of a tumour promoter in a number of in vitro systems. The effect is apparent at concentrations of diazepam which are clinically relevant. Diazepam also accelerated tumour growth in two different experimental animal cancers. Tranquillizer use was found to be greater in women with metastatic breast cancer at the time of diagnosis than in those without metastases. Further evaluation of the possible effects of diazepam and related drugs on human and animal cancers is urgently required.