A CRITICAL-APPRAISAL OF THE VALUE OF THE MOUSE CANCER BIOASSAY IN SAFETY ASSESSMENT

Substantial progress in understanding nongenotoxic or secondary mechan isms of tumorigenesis has been made over the past decade. However, the methods used in regulated studies for assessment of carcinogenic pote ntial in chemicals in development have not evolved significantly. Base d on the experience of over 30 yr of testing and the societal need to control costs, reevaluation of standard cancer rodent bioassay protoco ls is being done. Expert consensus after evaluating the results of ful l-scale rodent bioassays of both sexes in 2 species is that a reduced protocol is acceptable. After review of relevant data, it is our opini on that cancer hazard assessment in male and female rats only would be sufficient and that, in the future, mouse bioassays will not add sign ificant value on a routine basis. We are unable to find an example of a mouse tumorigenic finding that predicts a confirmed or probable huma n response with negative findings in a rat bioassay. The savings reali zed by eliminating mouse testing from routine protocols would be subst antial and better spent in expanding short-term studies to add to our understanding of chemical carcinogenesis.