Biology and therapeutic response of a mouse mammary adenocarcinoma (16/C) and its potential as a model for surgical adjuvant chemotherapy.

A mammary adenocarcinoma (16/C) was isolated and maintained in serial passage by transplantation of metastatic lung foci. This tumor originated as a spontaneous mammary adenocarcinoma in a C3H/He female mouse. It was selected as a model from greater than 50 mammary tumors studied because it was highly metastatic and because it responded to most of the agents reported to be active against breast cancer in women. Sc implanted 16/C tumors (in the 300--1000-mg range) metastasized to the lungs in greater than 75% of the mice and to the axillary lymph nodes in greater than 30%. This tumor has been tested for sensitivity to greater than 40 clinically used agents. Adriamycin was the most active single agent. Other active agents included cyclophosphamide, 5-fluorouracil, vincristine, melphalan, dibromodulcitol, maytansine, neocarzinostatin, palmO-ara-C, vinblastine, and VP-16-213. Agents most active against 40--1000-mg tumours were also most active against micrometastatic disease (eg, adriamycin). The converse was also true; agents inactive or marginally active against 40--1000-mg tumors were at best marginally active against micrometastatic disease (eg, BCNU). Tumors greater than 20 mg were not curable by chemotherapy alone, although adriamycin treatment caused complete regressions of 100--400-mg tumors in greater than 80% of the mice. Surgical removal of 300--1000-mg tumors plus therapy with adriamycin resulted in 40%--72% cures as compared to 0--26% cures with surgery only. Data resulting from treatment with other agents, singly and in combination, are presented.