Bacillus Calmette‐Guerin Immunotherapy Significantly Prolongs Survival of Animals with Prostate Cancer

Objectives: Bacillus Calmette-Guerin (BCG) is the treatment of choice for carcinoma in situ of the bladder, but its application to other cancers is very limited. The current study evaluates the effect of intralesional BCG in the PA3 rat prostate cancer model. Materials and Methods: One hundred five rats were randomized to four groups. Each group received 1 × 106 PA3 cells subcutaneously on experiment Day 0. On experimental Day 7, the groups received the first of six weekly treatments. Treatments consisted of saline solution, BCG 1 × 104 colony-forming units (cfu), BCG 1 × 105 cfu, and BCG 1 × 106 cfu. All animals were monitored for tumor growth throughout the duration of the experiment. Results: Animals receiving treatments with BCG 1 × 106 cfu exhibited the greatest reduction in tumor volume ([mean ± SD] 4130.0 ± 1738.3 mm3; p = 0.0738), followed by those receiving BCG 1 × 104 cfu (4527.6 ± 1932.7 mm3; p = 0.1093) and BCG 1 × 105 cfu (4838.2 ± 1889.9 mm3; p = 0.5218), compared to those receiving the saline solution control (5445.0 ± 3119.5 mm3). Animal survival on Day 60 after transplantation was significantly increased in the group receiving BCG 1 × 106 cfu (19 [73.1%] of 26 animals; p = 0.0326) when compared to those receiving the saline solution control (12 [44%] of 27 animals). Treatment with BCG 1 × 105 cfu (11 [42.3%] of 26 animals survived; p = 0.5479) and BCG 1 × 104 cfu (13 [50%] of 26 animals survived; p = 0.4484) also reduced survival compared to the saline solution control, but not to the level of significance. Conclusions: The consistent reduction in tumor growth and animal mortality in animals receiving intralesional BCG demonstrates antitumor activity in this aggressive model of prostate cancer. The greatest efficacy was seen with the highest dose of BCG, suggesting that higher doses may be optimal in this model. BCG immunotherapy of prostate cancer warrants clinical evaluation.