Experimental evaluation of nonspecific immunostimulation and chemotherapy in the intracranial tumor-bearing Fisher rat.

One hundred sixty rats bearing intracranial tumors were divided into groups of 10 to evaluate C-I interval +, effect of chemotherapy alone (BCNU), chemotherapy and C. parvum, and C. parvum alone in the rat tumor model. All therapy was administered intraperitoneally: BCNU -5.2 mg/kg (40% of LD10) on the 9th and 16th post tumor implant day, and C. parvum-1.4 mg regardless of the body weight and the 6th or 23rd day and 6th and 23rd post tumor implant day. An additional group received BCNU on the 9th and 16th day and C. parvum every 3rd day beginning with the 11th post implant day. It is concluded that C. parvum given before BCNU yields the greatest increase in survival in this animal system. Two or more injections were detrimental and injections after BCNU were of less value. C. parvum alone was minimally effective. If nonspecific immunostimulation is contemplated in this animal tumor system, it would appear to be best given before chemotherapy. This may relate to the brain as a "privileged immune site", or a peculiarity of the blood brain barrier in an intracranial lesion as it related to combined therapy.