Faculty Bibliography

BACKGROUND:The management of biochemical failure (BF) following external beam radiotherapy (EBRT) for prostate cancer is controversial, due to both the heterogeneous disease course following a BF and a lack of clinical trials in this setting. OBJECTIVE:We sought to characterize the natural history and predictors of outcome for patients experiencing BF in a large cohort of men with localized prostate cancer undergoing definitive dose-escalated EBRT. DESIGN, SETTING, AND PARTICIPANTS/METHODS:This retrospective analysis included 2694 patients with localized prostate cancer treated with EBRT at a large academic center. Of these, 609 experienced BF, defined as prostate-specific antigen (PSA) nadir + 2 ng/ml. The median follow-up was 83 mo for all patients and 122 mo for BF patients. INTERVENTION(S)/METHODS:All patients received EBRT at doses of 75.6-86.4 Gy. OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS/METHODS:The primary objective of this study was to determine predictors of distant progression at the time of BF. Cox proportional hazards models were used in univariate and multivariate analyses of distant metastases (DM), and a competing risks method was used to analyze prostate cancer-specific mortality (PCSM). RESULTS AND LIMITATIONS/CONCLUSIONS:From the date of BF, the median times to DM and PCSM mortality were 5.4 yr and 10.5 yr, respectively. Shorter posttreatment PSA doubling time, a higher initial clinical tumor stage, a higher pretreatment Gleason score, and a shorter interval from the end of radiotherapy to BF were independent predictors for clinical progression following BF. Patients with two of these risk factors had a significantly higher incidence of DM and PCSM following BF than those with zero or one risk factor. The main limitations of this study are its retrospective nature and heterogeneous salvage interventions. CONCLUSIONS:Clinical and pathologic factors can help identify patients at high risk of clinical progression following BF. PATIENT SUMMARY/RESULTS:In this report, we look at predictors of outcome for patients with prostate cancer recurrence, as determined by prostate-specific antigen (PSA) levels, following radiation treatment. We found that the approximate median times to distant metastasis and death from prostate cancer for patients in this situation were 5 yr and 10 yr, respectively. Furthermore, we found that patients with a rapid increase in PSA levels following treatment, a short time to PSA recurrence, invasion of extraprostatic organs, or a high Gleason score had worse outcomes.

PURPOSE/OBJECTIVE:To compare the potential benefits of continuous monitoring of prostate position and intervention (CMI) using 2-mm displacement thresholds during stereotactic body radiation therapy (SBRT) treatment to those of a conventional image-guided procedure involving single localization prior to treatment. METHODS AND MATERIALS/METHODS:Eighty-nine patients accrued to a prostate SBRT dose escalation protocol were implanted with radiofrequency transponder beacons. The planning target volume (PTV) margin was 5 mm in all directions, except for 3 mm in the posterior direction. The prostate was kept within 2 mm of its planned position by the therapists halting dose delivery and, if necessary, correcting the couch position. We computed the number, type, and time required for interventions and where the prostate would have been during dose delivery had there been, instead, a single image-guided setup procedure prior to each treatment. Distributions of prostate displacements were computed as a function of time. RESULTS:After the initial setup, 1.7 interventions per fraction were required, with a concomitant increase in time for dose delivery of approximately 65 seconds. Small systematic drifts in prostate position in the posterior and inferior directions were observed in the study patients. Without CMI, intrafractional motion would have resulted in approximately 10% of patients having a delivered dose that did not meet our clinical coverage requirement, that is, a PTV D95 of >90%. The posterior PTV margin required for 95% of the dose to be delivered with the target positioned within the PTV was computed as a function of time. The margin necessary was found to increase by 2 mm every 5 minutes, starting from the time of the imaging procedure. CONCLUSIONS:CMI using a tight 2-mm displacement threshold was not only feasible but was found to deliver superior PTV coverage compared with the conventional image-guided procedure in the SBRT setting.

BACKGROUND:Castration-resistant prostate cancer (CRPC) is a near uniformly fatal form of prostate cancer; however, information on time to development and predictors for progression to CRPC is limited. We report a detailed longitudinal study for development of CRPC in men initially treated with external beam radiotherapy (EBRT). METHODS:During 1991-2008, 2,478 patients with clinically localized prostate cancer were treated with dose-escalated EBRT at a single institution. The primary objective was to determine predictors of CRPC among men who failed definitive EBRT and progressed to salvage androgen-deprivation therapy (ADT). CRPC was defined as castrate levels of testosterone (<50 ng/dl) with progressive biochemical or radiographic disease. RESULTS:For the entire cohort (n = 2,478), the 10-year cumulative incidence rate for developing CRPC was 9.9%. For those that progressed to salvage ADT (n = 362), the 7-year cumulative incidence rates for developing CRPC from time of salvage ADT was 33.7%. Amongst this cohort, multivariable analysis demonstrated that PSA doubling-time (continuous; hazard ratio [HR], 0.98 [0.97-0.99], P < 0.001), higher Gleason score (HR, 1.96 [1.12-3.43]; P = 0.034), and duration of ADT at time of EBRT (continuous; HR, 1.02 [1.01-1.03]; P = 0.007) were associated with development of CRPC. CONCLUSIONS:This represents the first report of predictors of CRPC for patients treated with modern dose-escalated EBRT. We demonstrate that among the minority of patients not initially cured after EBRT, those treated with longer-course ADT have higher rates of resistance to the re-introduction of ADT. Future trials will need to test this subgroup with more aggressive or alternative forms of salvage therapies.

PURPOSE/OBJECTIVE:Small cell carcinoma of the urinary bladder (SCCB) is rare. We report our experience using definitive external beam radiation therapy (EBRT) as part of multimodality management of SCCB. METHODS AND MATERIALS/METHODS:Nineteen patients with locoregional SCCB were treated at our institution with EBRT between January 1994 and September 2012. Five patients had radiographic nodal disease. Eighteen patients received neoadjuvant (17/19; 89%) or concurrent (11/19: 58%) platinum-based chemotherapy. Acute (<90 days) and late (>90 days) toxicity was recorded using Common Terminology Criteria for Adverse Events, version 4. The Kaplan-Meier method was used for survival analysis and a log-rank test used to compare subsets of patients. RESULTS:Median follow-up was 26 months. Three patients had in-bladder recurrence (2-year local recurrence, 25%), 2 being noninvasive and successfully managed with transurethral resection and the third being invasive but managed with chemotherapy alone due to simultaneous distant metastases. No patient underwent salvage cystectomy. Six patients had recurrence distantly (2-year distant recurrence, 40%), predominantly bone metastases (n = 3). No patients developed brain metastases. Actuarial 2-year disease-free and overall survival was 51% and 78%, respectively. The 2-year distant metastasis-free survival for node-negative and node-positive patients was 76% and 26%, respectively (P = .04). The 2-year incidence of distant metastases for patients receiving ≥4 cycles of doublet chemotherapy was 27%, compared with 75% with less chemotherapy (P = .01). The incidence of grade ≥2 acute and late genitourinary or gastrointestinal toxicity was 69% and 7%, respectively. CONCLUSIONS:Definitive chemoradiation for locoregional SCCB is well tolerated, with encouraging local control and overall survival at 2 years.

PURPOSE/OBJECTIVE:To investigate the association between statin use and prostate cancer outcomes in intermediate- and high-risk patients treated with brachytherapy for prostate cancer. METHODS AND MATERIALS/METHODS:Between 1998 and 2010, 754 men with National Comprehensive Cancer Network intermediate- (n = 627) and high-risk (n = 127) prostate cancer were treated with prostate brachytherapy at our institution. Patients received either low-dose-rate or high-dose-rate brachytherapy as monotherapy or in combination with supplemental external beam radiotherapy. Two hundred eighty-five patients (37.8%) also received androgen-deprivation therapy. Two hundred seventy-three men (36.2%) were identified as taking statin medication before initiating radiation therapy. Prostate-specific antigen relapse-free survival (PSA-RFS), distant metastasis-free survival (DMFS), and overall survival were compared using log-rank tests. Associations of patient and treatment characteristics with outcomes were analyzed with univariate and multivariate regression. The median followup was 48 months. RESULTS:The 8-year PSA-RFS for intermediate-risk, high-risk, and all patients was 92.2%, 64.1%, and 87.7%, respectively. The 8-year DMFS was 97.1%, 82.9%, and 94.9%, respectively. The 8-year overall survival for the entire cohort was 86.6%. There were no significant differences between statin users and nonusers when stratified by risk group, nor when analyzed as a full cohort. On multivariate analysis, Gleason score 4 + 3 = 7 and >7 were significantly associated with worse PSA-RFS (p ≤ 0.003 and <0.001, respectively). Gleason score > 7 (p = 0.008) and the use of neoadjuvant androgen-deprivation therapy (p = 0.03) was associated with worse DMFS. Statin use did not significantly impact PSA-RFS or DMFS. CONCLUSIONS:Pretreatment statin use is not associated with improved outcomes in intermediate- and high-risk patients undergoing prostate brachytherapy-based regimens for prostate cancer.

PURPOSE/OBJECTIVE:To identify an anatomic structure predictive for acute (AUT) and late (LUT) urinary toxicity in patients with prostate cancer treated with low-dose-rate brachytherapy (LDR) with or without external beam radiation therapy (EBRT). METHODS AND MATERIALS/METHODS:From July 2002 to January 2013, 927 patients with prostate cancer (median age, 66 years) underwent LDR brachytherapy with Iodine 125 (n=753) or Palladium 103 (n=174) as definitive treatment (n=478) and as a boost (n=449) followed by supplemental EBRT (median dose, 50.4 Gy). Structures contoured on the computed tomographic (CT) scan on day 0 after implantation included prostate, urethra, bladder, and the bladder neck, defined as 5 mm around the urethra between the catheter balloon and the prostatic urethra. AUT and LUT were assessed with the Common Terminology Criteria for Adverse Events, version4. Clinical and dosimetric factors associated with AUT and LUT were analyzed with Cox regression and receiver operating characteristic analysis to calculate area under the receiver operator curve (ROC) (AUC). RESULTS:Grade ≥2 AUT and grade ≥2 LUT occurred in 520 patients (56%) and 154 patients (20%), respectively. No grade 4 toxicities were observed. Bladder neck D2cc retained a significant association with AUT (hazard ratio [HR], 1.03; 95% confidence interval [CI], 1.03-1.04; P<.0001) and LUT (HR, 1.01; 95% CI, 1.00-1.03; P=.014) on multivariable analysis. In a comparison of bladder neck with the standard dosimetric variables by use of ROC analysis (prostate V100 >90%, D90 >100%, V150 >60%, urethra D20 >130%), bladder neck D2cc >50% was shown to have the strongest prognostic power for AUT (AUC, 0.697; P<.0001) and LUT (AUC, 0.620; P<.001). CONCLUSIONS:Bladder neck D2cc >50% was the strongest predictor for grade ≥2 AUT and LUT in patients treated with LDR brachytherapy. These data support inclusion of bladder neck constraints into brachytherapy planning to decrease urinary toxicity.

PURPOSE/OBJECTIVE:To assess outcomes and toxicity of high-dose-rate intraoperative radiation therapy (HDR-IORT) in the management of pediatric sarcoma. METHODS AND MATERIALS/METHODS:Seventy-five pediatric patients underwent HDR-IORT for sarcoma from May 1993 to November 2013. The median age was 9 years old (36 patients were ≤ 6 years old). HDR-IORT was part of initial therapy in 37 patients (49%) and for recurrent disease in 38 patients (51%). Forty-one patients (55%) received HDR-IORT and postoperative external beam RT (PORT), and 22 patients (29%) were previously treated with external beam radiation therapy to the IORT site. Local control (LC), overall survival (OS) and event-free survival (EFS) were estimated using Kaplan-Meier methods. RESULTS:At a median follow-up of 7.8 years for surviving patients, 5-year projected rates of LC, EFS, and OS were 63% (95% confidence interval [CI] 50%-76%), 33% (95% CI 21%-45%), and 43% (95% CI 30%-55%), with a median survival of 3.1 years. The 5-year LC, EFS, and OS rates for patients with recurrent disease were 46% (95% CI, 28%-64%), 30% (95% CI, 13%-46%), and 36% (95% CI, 18%-54%). Acute toxicity ≥ grade 3 occurred in 2 (2.5%) treatments; late toxicity ≥ grade 3 occurred in 4 (5.3%) patients 0.3-9.9 years after HDR-IORT. The incidence of toxicity ≥ grade 3 was not associated with HDR-IORT applicator size, HDR-IORT dose, prior RT or PORT, or prior or postoperative chemotherapy, but all toxicity ≥ grade 3 occurred in patients ≤ 6 years treated with HDR-IORT doses ≥ 12 Gy. CONCLUSIONS:HDR-IORT is a well-tolerated component of multimodality therapy for pediatric sarcoma, allowing additional local treatment while reducing external beam exposure. Taking clinical considerations into account, doses between 8-12 Gy are appropriate for HDR-IORT in patients ≤ 6 years of age.