The radial distance of extraprostatic extension of prostate carcinoma - Implications for prostate brachytherapy

BACKGROUND. Extraprostatic extension (EPE) is an unfavorable prognostic fac tor in patients with prostate carcinoma. Prior studies have reported the li near extent of EPE measured circumferentially along the edge of the prostat e. In this study, the authors defined and evaluated a novel measure of EPE in a large series of radical prostatectomy specimens. These results have im portant clinical implications in the management of localized prostate carci noma by brachytherapy and other modalities. METHODS, The authors reviewed the preoperative records and biopsy findings from 376 patients who underwent radical retropubic prostatectomy between Se ptember 1991 and June 1993. Whole mount radical prostatectomy specimens wer e examined, and the location of EPE for each specimen was recorded. The rad ial EPE distance was measured perpendicular to the edge of the prostate. Fo r specimens with multiple EPE sites, the maximum radial EPE distance was re corded. Established eligibility criteria for prostate brachytherapy were ev aluated using these results, with emphasis placed on achieving adequate rad iation dose coverage 3-5 mm beyond the capsule or the edge of the prostate. RESULTS, EPE was identified in 105 of 376 specimens (28%) at 248 sites. The radial EPE distance in these specimens had a mean of 0.8 mm (range, 0.04-4 .4 mm) and a median of 0.5 mm. Of these 105 patients, the median and mean p reoperative prostate specific antigen (PSA) concentrations were 11.8 ng/mL and 17.9 ng/mL, respectively. The mean and range of the Gleason score and p rostate volume for all specimens were 6.3 (range, 3-9) and 39 cc (range, 8- 294 cc), respectively. In 107 patients who met the selection criteria for p rostate brachytherapy eligibility of a PSA level < 10 ng/mL, Gleason score < 7, and gland volume < 60 cc, the maximum and mean radial EPE distances we re 0.6 mm and 0.03 mm, respectively. CONCLUSIONS, The radial distance of EPE is an important measure that influe nces treatment strategies for patients with localized prostate carcinoma. C urrently described criteria for the treatment of early stage prostate carci noma by brachytherapy alone appear satisfactory to ensure effective radiati on dose coverage of EPE of prostate tumors. Treating the prostate with a 3- 5 mm margin by brachytherapy would encompass all known tumor in approximate ly 99% of the specimens examined in this study. Cancer 1999;85:2630-7. (C) 1999 American Cancel Society.