ALTERNATIVE TESTS - CARCINOGENESIS AS AN EXAMPLE

Acceptance of new tests that are alternatives to currently used toxico logy tests is a topic of considerable importance in the field of toxic ology. Carcinogenicity testing today normally includes 2-year studies in rats and mice of both sexes, following widely accepted procedures f or husbandry; selection of dose levels; pathology and toxicity observa tions; and statistical interpretation of tumor data. These studies are usually preceded by tests for genetic toxicity and subchronic toxicit y studies to select dose levels for the 2-year studies. Although these data are used for quantitative risk assessment, the mechanistic basis for effects is usually unknown. The series of studies is very expensi ve and requires 5 years or more to conduct. Alternative approaches are being developed that would provide more mechanistic information and h opefully would permit decisions to be made about carcinogenic potentia l without the need to conduct 2-year studies in rats and mice of both sexes. Decisions could be based on a profile of data rather than on th e result of one test. Procedures for regulatory acceptance of new appr oaches for carcinogenicity testing are critical to future progress.