Further observations on the inhibition of tumor growth by Corynebacterium parvum with cyclophosphamide. II. Effect of cortisone acetate.

Studies from this laboratory have demonstrated that the administration of cyclophosphamide (CY) and Corynebacterium parvum (CP) over a prolonged time to C3H mice with established measurable tumors resulted in complete arrest of tumor growth as well as partial and complete regressions in many instances. A study of the effect of two different doses of cortisone acetate (CA), administered two or five times weekly, on the tumor inhibitory properties of this chemoimmunotherapeutic regimen indicated that the addition of a corticosteroid to the CY-CP combination did not alter its tumor-inhibitory properties. There was no significant change when CA was administered with CP; however, tumor inhibition was enhanced to a degree approaching statistical significance when CA was added to CY at dose levels of 1.5 and 2.5 mg twice weekly. These results demonstrated that it may be possible in treatment of humans to administer a steroid in combination with a chemoimmunotherapeutic regimen without inhibition of the regimen's antitumor effects.