Active immunotherapy with Corynebacterium parvum and chemotherapy in murine fibrosarcomas.

Corynebacterium parvum used alone to enhance immunological reactivity produced transient inhibition of the growth of chemically induced isogenic mouse tumours. Attempts were made to combine C. Parvum with cyclophosphamide to see whether this would increase the latter's effectiveness in inhibiting early but established tumours. Of the various regimens tested, the administration of the C. parvum 12 days after a single dose of chemotherapy produced dramatic inhibition of tumour growth and resulted in complete and lasting regressions in up to 70% of tumour-bearing animals. The most important variable in this regimen is the time between the chemotherapy and the subsequent immunotherapy.It is possible that non-specific active immunotherapy with agents such as C. parvum may be a valuable adjunct to the conventional cyto-reductive treatments of cancer, but the time of administration of such therapy is probably critical for each tumour and for each chemotherapeutic regimen.