Predictors of extracapsular extension and its radial distance in prostate cancer: implications for prostate IMRT, brachytherapy, and surgery.
OBJECTIVE
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 attemptingto adhere to normal tissue dose tolerances. In this study, we attempted to find predictors of extracapsular extension (ECE) and its radial distance.


METHODS
Pathological assessment of ECE and its radial distance was performed on 712 radical prostatectomy specimens. Preoperative data (initial prostate-specific antigen, 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 preoperative parameters except ultrasound volume were able to predict the presence of ECE. However, none of them was predictive of the radial ECE distance. In this group, the median and the range of the maximum depth of invasion (radial extension from the capsule) were 2.00 and 0.5-12.00 mm, respectively. The mean radial distance from the capsule was 2.93 mm, SD +/- 2.286 mm. All subgroups had some patients with radial extension ranging from 0-2 mm, 2-5 mm, to > 5 mm. Only patients with a prostate-specific antigen of 0-4 ng/mL had no extension > 5 mm.


CONCLUSIONS
This is the largest series in the literature thus far that quantitatively assesses radial extracapsular extension. Coverage of subclinical disease must be addressed carefully before successful implementation of intensity-modulated radiation therapy, brachytherapy, or prostatectomy in order to avoid geographical miss.
Teh
Bin S
BS
Department of Radiology, Section of Radiation Oncology, The Methodist Hospital, Houston, Texas 77030, USA. bteh@bcm.tmc.edu
Bastasch
Michael D
MD
Mai
Wei-Yuan
WY
Butler
E Brian
EB
Wheeler
Thomas M
TM
D000328:Adult; D000368:Aged; D001918:Brachytherapy / Q000379:methods; D006801:Humans; D008297:Male; D008875:Middle Aged; D009361:Neoplasm Invasiveness; D011379:Prognosis; D017430:Prostate-Specific Antigen / Q000032:analysis; D011468:Prostatectomy; D011471:Prostatic Neoplasms / Q000473:pathology* / Q000532:radiotherapy* / Q000601:surgery; D018714:Radiotherapy, Adjuvant
D017430:Prostate-Specific Antigen