Defining the implant treatment volume for patients with low risk prostate cancer: does the anterior base need to be treated?

Abstract

An increased incidence of acute urinary retention has been reported after interstitial prostate radiation therapy when the anterior base of the prostate gland receives 100% of the prescription dose. The frequency of prostate cancer in this location as a function of the pre-treatment prostate specific antigen (PSA), biopsy Gleason score, and 1992 American Joint Commission on Cancer Staging (AJCC) was determined. One hundred four men treated at the Brigham and Women's Hospital with radical prostatectomy for clinically localized prostate cancer between 1995-1996 comprised the study population. Prostatectomy specimens were whole mounted and the location of each tumor foci enumerated. Of 269 foci of prostate cancer found in 39 low-risk prostate cancer patients (PSA < 10 ng/ml, biopsy Gleason score < or = 6, and 1992 AJCC clinical stage T1c,2a), a single focus (0.37%) was noted in the anterior base. Conversely, 20/355 (5.6%) and 18/251 (7.2%) tumor foci were noted in the anterior base in 43 patients with intermediate risk and 24 patients with high-risk disease, respectively. A new definition of the treatment volume excluding the anterior base for low-risk prostate cancer patients may be justified.