Restraint-induced inhibition of 7,12-dimethylbenz[a]anthracene-induced mammary tumors: relation to stages of tumor development.

Experiments on the use of chronically applied restraint to reduce the number of mammary tumors developing in response to treatment of rats with 7,12-dimethylbenz[a]anthracene indicated that this inhibitory effect was largely due to restraint applied after the induction period; preinduction restraint and induction period restraint had no significant effect on tumor development. After termination of the restraint treatment, the rate at which new tumors appeared first increased and then decreased. Restraint did not affect the proportion of tumors regressing after ovariectomy.