Prostate Specific Antigen Five Years Following Stereotactic Body Radiation Therapy (Sbrt) For Low And Intermediate Risk Prostate Cancer: An Ablative Procedure?

123Background: Our previous work on early PSA kinetics following prostate SBRT showed that an initial rapid and then slow PSA decline may result in very low PSA nadirs. This retrospective study sought to evaluate the PSA nadir 5 years following SBRT for low and intermediate risk prostate cancer (PCa). Methods: 65 low and 80 intermediate risk PCa patients were treated definitively with SBRT at Georgetown University Hospital between January 2008 and October 2011. All patients were treated to 35-37.5 Gy in 5 fractions delivered via the CyberKnife Radiosurgical System. Patients who received androgen deprivation therapy were excluded from this study. Pre- and post-treatment PSA and total testosterone levels were obtained during routine follow up visits. Biochemical relapse was defined as a PSA rise u003e 2 ng/mL above the nadir and analyzed using the Kaplan Meier method. The PSA nadir was defined as the lowest PSA value prior to biochemical relapse or as the lowest value recorded during follow up. Prostate ablatio...