Immunotherapy of an established rat mammary adenocarcinoma (13762A) with intratumor injection of Corynebacterium parvum.

We studied the effects of intratumor injection of Corynebacterium parvum vaccine on the survival of 13762A tumor-bearing rats. Vaccine injection of established (7-day-old) tumors produced dose-related prolongation of survival and cured some animals. Although 30 to 40% of the vaccine-injected primary tumors regressed, recurrences and continued growth of metastases ultimately killed one-fourth of the regressors. Rats given 1500 microgram of C. parvum intratumorally at 7 days, with or without later primary tumor excision at 20 days were cured at a rate of 10 to 40%. Repeated injections improved the results (60%). C. parvum injections delayed until 12 and 17 days were ineffective. Cured rats were immune to rechallenge with 13762A tumor.