Site-directed metastasis: a model to study site variations in treatment response.

A model for the site-directed metastasis of a transplantable rat mammary carcinoma is described. The R3230AC tumor is a moderately well differentiated, phenotypically stable tumor which arose in a Fischer 344 rat and resembles human breast carcinoma in being hormonally sensitive, poorly immunogenic, and sensitive to radiation and chemotherapeutic agents. Metastases with this tumor can be consistently produced at specific sites (lung, liver, or subcutaneous) in a reproducible manner by the methods described in this paper. This model appears ideal for the evaluation of site-specific variation in response to treatment modalities.