Suramin as adjuvant therapy with radical prostatectomy

Suramin is a newer agent employed in the management of prostate cancer. One suggested method of action is growth factor inhibition. While suramin has been employed to treat advanced disease its adjuvant role remains unexplored. To address this question we have employed a new model: the orthotopic placement of the Dunning AT-3 tumor. The purpose of this research was to assess the efficacy of adjuvant therapy in controlling residual disease. The method consisted of the injection of 2.4 to 2.6 x 10⁶ AT-3 cells (harvested from flank tumors) into the ventral prostates of 29 Copenhagen X Fischer rats. The animals were then divided into four groups: 1) untreated controls (6 rats); 2) ventral prostatectomy only (10 rats); 3) ventral prostatectomy plus suramin (300 mg/Kg) on post-op day 3 (5 rats); and 4) ventral prostatectomy plus cytoxan (50 mg/Kg) on post-op day 3 (8 rats). Prostatectomies were performed 10-12 days following AT-3 cell inoculation. Animals were sacrificed 10 days following prostatectomy, autopsied, and residual disease weighed. All operating procedures: tumor cell inoculations, ventral prostatectomies, and necropsies were performed microsurgically employing a Zeiss operating microscope. The results (in mean tumor weights) were: Group 1, 20 ± 1.4 gms; Group 2, 6.7 ± 11.5 gms; Group 3, 2.7 ± 3.8 gms; and Group 4, 2.2 ± 2.5 gms. The differences between control and all treatment groups were significant: Group 1 vs. Group 2, P < 0.02; and Group 1 vs. Groups 3 and 4, P < 0.001. We conclude that prostatectomy resulted in a diminished weight of residual disease. Of more importance was the fact that adjuvant therapy further reduced residual disease. The orthotopic placement of the Dunning tumor may serve as a model to evaluate the place of suramin following radical prostatectomy.