In the first reported results of 18 patients with locally recurrent prostate cancer, a single dose, dose escalation study was conducted using an ADV vector with the HSV thymidine kinase gene (Adv/HSV-tk) injected transrectally into one lobe of the prostate followed by ganciclovir (GCV; Herman et al., 1999). Here, TKT is linked to prostate cancer.