Predictors of extracapsular extension (ECE) and its radial distance in prostate cancer: Implications for prostate IMRT, brachytherapy, and surgery

Purpose: Tightly constricted isodose lines are generated using brachytherapy or intensity modulated radiation therapy (IMRT) treatment planning systems for prostate cancer. Definition of margins that encompass subclinical disease extension is important to maximize dose escalation while attempting to adhere to normal tissue dose tolerances. We attempted to find predictors of ECE and its radial distance. Materials and Methods: Pathologic assessment of ECE and its radial distance was performed on 712 radical prostatectomy specimens. Pre-operative data: initial PSA, clinical stage, ultrasound volume, and biopsy Gleason score, were evaluated for their ability to predict the presence of ECE and its radial distance. Results: Measurable disease was noted outside the prostatic capsule in 185 of 712 (26.0%) specimens. All pre-operative parameters, except for ultrasound volume, were able to predict the presence of ECE. None of them was predictive of the radial ECE distance, however. In this group, median and range of the maximum depth of invasion (radial extension from the capsule) were 2.00 mm and 0.5-12.00 mm respectively. The mean radial distance from the capsule was 2.93mm, SD ±2.286 mm. All subgroups had some patients with radial extension ranging from 0-2mm, 2-5mm, to 5mm. Only patients with a PSA of 0-4 ng/mL had no extension < 5 mm. Conclusions: This is the largest series in the literature quantitatively assessing radial extracapsular extension. Coverage of subclinical disease must be addressed carefully before successful implementation of IMRT, brachytherapy, or prostatectomy in order to avoid geographical miss.