His prostate-specific antigen level fell to 0.38 ng/mL after surgery; he was therefore prescribed radiation and androgen-deprivation therapies that controlled the cancer for more than 1 year.<h4>Conclusions</h4>We encountered a case showing direct peritoneal invasion of prostate cancer during robot-assisted radical prostatectomy. This evidence concerns the gene KLK3 and Familial prostate cancer.