Accurate predictions of tumor growth in vivo: the subrenal capsule implant site.

An assay system with exquisite predictive qualities is described for four animal tumors: two rat mammary adenocarcinomas, R3230 Ac and 13762; a mouse papillary mammary carcinoma, MXT; and the mouse reticulum cell sarcoma M5076. The tumors were implanted beneath the renal capsule of syngeneic hosts (BDF1 mice or Fischer 344 rats). This site is readily accessible, well-protected, and provides a rich vascular bed, thus controlling many of the variables involved in neoplastic growth. The growth of each implant was recorded as a function of time and/or the initial tumor size. The absolute growth of each of the tumors could be predicted accurately from a simple linear regression analysis of time (i.e., number of days post-implant). Even more accurate predictions of tumor growth were obtained when both variables (days post-implant and initial implant size) were evaluated by multiple regression analysis. The subrenal capsule tumor implant site provides a superior model system to investigate the effects of biological response modifiers and other immunological manipulations on tumor growth in intact normal immunocompetent animals.