Phase II trial of GM-CSF in advanced prostate cancer

Objectives. Prostate-specific antigen only disease progression following definitive therapy is significant therapeutic dilemma. The benefit of hormonal therapy remains unproven and is associated with significant toxicity, more pronounced with chronic use. Biochemical progression following hormonal therapy has no standard treatment. New approaches to the management of this subset of patients are needed. A previous study in advanced prostate cancer demonstrated biologic activity of granulocyte macrophage-colony stimulating factor. The purpose of this study was to evaluate the activity of granulocyte macrophage-colony stimulating factor in a less heavily pretreated population. Materials and methods. Sixteen patients with advanced prostate cancer, 7 hormonally naive, and 9 androgen independent, were treated with granulocyte macrophage-colony stimulating factor administered subcutaneously at 250 mug three times a week for up to 6 months. Prostate-specific antigen measurements were obtained every 2 weeks. Results. No patient achieved an objective response. Six patients demonstrated a 10-15% decline in their baseline prostate-specific antigen which was maintained during the entire treatment period. Five of these 6 patients demonstrated a rise in their prostate-specific antigen following study completion. Therapy was well tolerated, with only 1 grade 3 event which was not treatment-related. Conclusions. Granulocyte macrophage-colony stimulating factor demonstrates modest biologic evidence of activity in prostate cancer as manifested by prostate-specific antigen response. Further investigation of the mechanism of activity and additional clinical evaluation of this agent seems warranted.