Immunotherapy of an experimental adenocarcinoma of the prostate

We have developed and tested a fractionated, purified and deproteinized emulsion of a mycobacterial cell wall (MCW) and report on a controlled study of this compound in the treatment of the experimental R3327-H adenocarcinoma of the prostate. The intraperitoneal route of administration was found ineffective at the weekly dose of 500 micrograms. The intratumoral administration of 1000 micrograms of MCW exhibited significant antitumor activity. Tumors larger than 2.2 cm.3 in volume showed evidence of temporary regression, but no cures were recorded in these animals. Complete tumor regression was found in 50% of the rats with tumor volumes less than 2.2 cm.3 at the onset of treatment. The animals in this group not responding initially were treated with a second 3-week course of MCW which resulted in complete tumor regression in one-half of the animals, for a total cure rate, in the smaller tumor cohort, of 75%. Mycobacterial cell wall is an effective biological response modifier in the Dunning R3327-H adenocarcinoma of the prostate in Copenhagen rats. Additional studies to elucidate the effect of the compound in relation to dose and tumor volume are underway.