Faculty Bibliography

PURPOSE/OBJECTIVE:To investigate whether pretreatment endorectal magnetic resonance imaging (MRI) findings can predict biochemical relapse in patients with clinically localized prostate cancer treated with external beam radiation therapy (EBRT). METHODS AND MATERIALS/METHODS:Between January 2000 and January 2002, 224 patients (median age, 69 years; age range, 45-82 years) with biopsy-proven prostate cancer underwent endorectal MRI before high-dose (≥81Gy) EBRT. The value of multiple clinical and MRI variables in predicting prostate-specific antigen (PSA) relapse at 5 years was determined by use of univariate and multivariate stepwise Cox regression. Clinical variables included pretreatment PSA, clinical T stage, Gleason score, use of neoadjuvant hormonal therapy, and radiation dose. Magnetic resonance imaging variables, derived from retrospective consensus readings by two radiologists, were used to measure intraprostatic and extraprostatic tumor burden. RESULTS:After a median follow-up of 67 months, PSA relapse developed in 37 patients (16.5%). The significant predictors of PSA relapse on univariate analysis were pretreatment PSA, clinical T stage, and multiple MRI variables, including MRI TN stage score; extracapsular extension (ECE) status; number of sextants involved by ECE, all lesions, or index (dominant) lesion; apical involvement; and diameter and volume of index lesion. Pretreatment PSA and ECE status were the only significant independent predictors on multivariate analysis (p < 0.05 for both). Extracapsular extension status was associated with the highest hazard ratio, 3.04; 5-year PSA relapse rates were 7% for no ECE, 20% for unilateral ECE, and 48% for bilateral ECE. CONCLUSIONS:Magnetic resonance imaging findings can be used to predict post-EBRT PSA relapse, with ECE status on MRI and pretreatment PSA being significant independent predictors of this endpoint.

OBJECTIVE:To determine if the location and number of positive surgical margins (PSMs) after radical prostatectomy (RP) are associated with recurrence after salvage external beam radiation therapy (sEBRT). PATIENTS AND METHODS/METHODS:We retrospectively reviewed the medical records of 60 patients with PSMs who underwent three-dimensional conformal sEBRT for biochemical recurrence (BCR) or clinically detected local recurrence after RP between 1996 and 2007. PSMs were categorized as present or absent at three locations, and patients were classified as having either one or more than one PSM. BCR after RP was defined as a prostate-specific antigen (PSA) level of ≥ 0.1 ng/mL. BCR after sEBRT was defined as a serum PSA level of ≥ 0.1 ng/mL above the PSA nadir after sEBRT. RESULTS:In all, 24 (40%) patients had more than one PSM. Overall, the most common location of a PSM was the posterior prostate with 40 (66%) patients having a positive posterior margin. The location of PSMs was not significantly associated with secondary BCR (global P= 0.8). There was a borderline result between the number of PSMs and BCR: men with more than one PSM were less likely to recur compared with those with only one PSM (hazard ratio 0.42; P= 0.067). CONCLUSIONS:This is the first study to specifically analyse location and number of PSMs as prognostic factors for men who undergo sEBRT. There was no evidence to suggest that the location of a PSM predicted secondary BCR. Further research is needed to determine whether the number of PSMs is an important predictor of BCR after sEBRT.

OBJECTIVES/OBJECTIVE:To evaluate the use of real-time kilovoltage cone-beam computed tomography (CBCT) during prostate brachytherapy for intraoperative dosimetric assessment and correcting deficient dose regions. METHODS:A total of 20 patients were evaluated intraoperatively with a mobile CBCT unit immediately after implantation while still anesthetized. The source detector system was enclosed in a circular CT-like geometry with a bore that accommodates patients in the lithotomy position. After seed deposition, the CBCT scans were obtained. The dosimetry was evaluated and compared with the standard postimplantation CT-based assessment. In 8 patients, the deposited seeds were localized in the intraoperative CBCT frame of reference and registered to the intraoperative transrectal ultrasound images. With this information, a second intraoperative plan was generated to ascertain whether additional seeds were needed to achieve the planned prescription dose. The final dosimetry was compared with the postimplantation scan assessment. RESULTS:The mean differences between the dosimetric parameters from the intraoperative CBCT and postimplant CT scans were < .5% for percentage of volume receiving 100% of the prescription dose, minimal dose received by 90% of the prostate, and percentage of volume receiving 150% of the prescription dose. The minimal dose received by 5% (maximal dose) of the urethra differed by 8% on average and for the rectum an average difference of approximately 18% was observed. After fusion of the implanted seed coordinates from the intraoperative CBCT scans to the intraoperative transrectal ultrasound images, the dosimetric outcomes were not significantly different from the postimplantation CT dosimetric results. CONCLUSIONS:Intraoperative CT-based dosimetric evaluation of prostate permanent seed implantation before anesthesia reversal is feasible and might avert misadministration of dose delivery. The dosimetric measurements using the intraoperative CBCT scans were dependable and correlated well with the postimplant diagnostic CT findings.