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Combination external beam radiation and brachytherapy boost with androgen deprivation for treatment of intermediate-risk prostate cancer
Long-term results of CALGB 99809
Article first published online: 4 MAR 2011
Copyright © 2011 American Cancer Society
Volume 117, Issue 24, pages 5579–5588, 15 December 2011
How to Cite
Hurwitz, M. D., Halabi, S., Archer, L., McGinnis, L. S., Kuettel, M. R., DiBiase, S. J. and Small, E. J. (2011), Combination external beam radiation and brachytherapy boost with androgen deprivation for treatment of intermediate-risk prostate cancer. Cancer, 117: 5579–5588. doi: 10.1002/cncr.26203
- Issue published online: 4 MAR 2011
- Article first published online: 4 MAR 2011
- Manuscript Accepted: 24 MAR 2011
- Manuscript Revised: 21 MAR 2011
- Manuscript Received: 19 JAN 2011
- cooperative group trial;
- hormonal therapy
Combined transperineal prostate brachytherapy and external beam radiation therapy (EBRT) is widely used for treatment of prostate cancer. Long-term efficacy and toxicity results of a multicenter phase 2 trial assessing combination of EBRT and transperineal prostate brachytherapy boost with androgen deprivation therapy (ADT) for intermediate-risk prostate cancer are presented.
Intermediate-risk patients per Memorial Sloan-Kettering Cancer Center/National Comprehensive Cancer Network criteria received 6 months of ADT, and 45 grays (Gy) EBRT to the prostate and seminal vesicles, followed by transperineal prostate brachytherapy with I125 (100 Gy) or Pd103 (90 Gy). Toxicity was graded using the National Cancer Institute Common Toxicity Criteria version 2 and Radiation Therapy Oncology Group late radiation morbidity scoring systems. Disease-free survival (DFS) was defined as time from enrollment to progression (biochemical, local, distant, or prostate cancer death). In addition to the protocol definition of biochemical failure (3 consecutive prostate-specific antigen rises >1.0 ng/mL after 18 months from treatment start), the 1997 American Society for Therapeutic Radiology and Oncology (ASTRO) consensus and Phoenix definitions were also assessed in defining DFS. The Kaplan-Meier method was used to estimate DFS and overall survival.
Sixty-one of 63 enrolled patients were eligible. Median follow-up was 73 months. Late grade 2 and 3 toxicity, excluding sexual dysfunction, occurred in 20% and 3% of patients. Six-year DFS applying the protocol definition, 1997 ASTRO consensus, and Phoenix definitions was 87.1%, 75.1%, and 84.9%. Six deaths occurred; only 1 was attributed to prostate cancer. Six-year overall survival was 96.1%.
In a cooperative setting, combination of EBRT and transperineal prostate brachytherapy boost plus ADT resulted in excellent DFS with acceptable late toxicity for patients with intermediate-risk prostate cancer. Cancer 2011;. © 2011 American Cancer Society.
Combined external beam with brachytherapy boost is commonly used for treatment of prostate cancer. Particularly for patients with intermediate-risk disease, this approach allows for coverage of the prostate and seminal vesicles with the margin achieved with external beam radiation therapy (EBRT) combined with a high-dose boost to the prostate with brachytherapy.
Although it was routinely used as an approach to prostate cancer therapy since the late 1980s, reports of results of this approach in the 1990s were limited to single-institution series. These series indicated that combined modality therapy could be safely administered with promising efficacy results.1-3 In recognition of the growing use and success of this approach to treatment of prostate cancer at individual centers of excellence, in the late 1990s both the Cancer and Leukemia Group B (CALGB) and the Radiation Therapy Oncology Group (RTOG) initiated multicenter phase 2 trials to assess the use of combined modality therapy as applied across a broad range of institutions through the cooperative research group mechanism.
CALGB 99809 was specifically designed to assess the feasibility, toxicity, and efficacy of combined modality therapy for treatment of patients with intermediate-risk prostate cancer. Patients were uniformly treated with EBRT to the prostate and seminal vesicles followed by low dose rate (LDR) prostate brachytherapy boost with 6 months of androgen deprivation therapy (ADT). Long-term results of this study are now presented.
MATERIALS AND METHODS
All patients had histologically confirmed adenocarcinoma of the prostate. A combination of clinical stage, pretreatment prostate-specific antigen (PSA), and biopsy Gleason score was used to define patients with clinically localized intermediate-risk prostate cancer criteria as per the Memorial Sloan-Kettering Cancer Center risk stratification criteria as follows: clinical T1 or T2 classification with PSA ≥10 and <20 ng/mL and Gleason score ≤6 or PSA <10 ng/mL and Gleason score ≥7, or T3a with PSA <10 and Gleason score ≤6 were eligible for the study. Patients with clinical evidence of nodal disease, N1, or evidence of metastases, M1, were excluded.
An Eastern Cooperative Oncology Group performance status of 0 to 2 was required. Patients had no prior treatment for prostate cancer except <4 weeks of ADT, no prior transurethral resection of the prostate, and a prostate size determined by transrectal ultrasound at the time of biopsy or subsequent imaging of <60 mL. Six months of luteinizing hormone-releasing hormone (LHRH) agonist therapy with either leuprolide acetate or goserelin acetate was administered before initiation of EBRT. EBRT was required to start within a month of initiation of LHRH agonist therapy. Four weeks of oral antiandrogen therapy with either flutamide or bicalutamide was recommended but not required at the start of LHRH agonist therapy to prevent a testosterone flare.
Enrolling institutions had experience with prostate ultrasound brachytherapy with at least 50 documented cases performed before registering patients for the study. All participants signed an institutional review board-approved, protocol-specific informed consent form in accordance with federal and institutional guidelines. Patient registration and data collection were managed by the CALGB Statistical Center. Data quality was ensured by careful review of data by CALGB Statistical Center staff and by the study chairperson. Statistical analyses were performed by CALGB statisticians.
EBRT inclusive of the prostate and seminal vesicles was administered with 3-dimensional conformal technique using ≥6-MV photons to 45 gray (Gy) in 25 fractions. International Commission on Radiation Unites and Measurements 50 guidelines and nomenclature were used for the study. The prescribed dose was defined on the central axis at the intersection of the beams. A total dose variation of −5% to +7% from the prescription point dose was allowed. The clinical target volume (CTV) was defined as the prostate and seminal vesicles. A planning target volume was applied to the CTV such that a block margin of 1.5 to 2 cm was applied around the CTV. Dose to 25% of the bladder and 50% of the rectum, defined 2 cm above to 2 cm below the CTV in the anteroposterior projection, was limited to 45 Gy. A daily fraction of 1.8 Gy was administered 5 days per week for 5 weeks.
Brachytherapy was performed 2 to 4 weeks after completion of EBRT by interstitial implantation using either I125 or Pd103. Preplanning was required via transrectal ultrasound performed within 2 weeks before implant; however, intraoperative adjustment in planning was allowed. The brachytherapy CTV was defined as the prostate identified via transrectal ultrasound with no margin. Prescribed dose to the CTV defined per International Commission on Radiation Units and Measurements 58 guidelines as the transrectal ultrasound-defined prostate was 100 Gy for I125 (American Association of Physicists in Medicine Task Group 43) or 90 Gy for Pd103 (as per dosimetric information provided by the vendor) in addition to 45 Gy EBRT. Source strength was required to be 0.30 to 0.50 U (0.24-0.40 mCi) for I125 and 1.04 to 1.30 U (0.8-1.0 mCi) for Pd103. A postimplant computed tomography scan was obtained 3 to 5 weeks after implant with axial images ≤5 mm thick obtained from at least 2 cm cephalad to the base of the prostate to 2 cm caudad from the apex of the prostate.
Toxicity was graded according to the National Cancer Institute Common Toxicity Criteria (CTC) version 2 and Radiation Therapy Oncology Group late radiation morbidity scoring systems. Late toxicity was defined as any toxicity persisting or occurring >9 months after prostate implant. Patients were seen in follow-up per protocol guidelines at 3 to 5 weeks postimplant, then at 3-month intervals until 2 years out from implant, every 6 months for Years 2 to 4, and annually thereafter. At each follow-up through Year 4, PSA, testosterone, digital rectal exam, hemoccult, and toxicity analysis including American Urologic Association symptom assessment were required. A central review of toxicity reporting was performed by the study chair (M.D.H.) to ensure accuracy and uniformity of toxicity scoring with any changes made in scoring documented with supporting information provided by the submitting institution to ensure transparency of the audit process.
Statistical Design and Data Analysis
The primary endpoints were acute and late toxicity of EBRT and brachytherapy in patients with clinically localized intermediate-risk prostate cancer who underwent androgen deprivation. Acute toxicities were defined according to the CALGB expanded CTC version 2, and late toxicities were defined according to the RTOG late radiation morbidity scoring criteria. Secondary endpoints were biochemical failures, disease-free survival (DFS), and overall survival (OS). DFS was defined as time from enrollment to first observed progression (biochemical, local, distant) or prostate cancer death. In addition to the protocol definition of biochemical failure (3 consecutive PSA rises >1.0 ng/mL after 18 months from start of treatment), the 1997 American Society for Therapeutic Radiology and Oncology (ASTRO) consensus definition and Phoenix (nadir + 2) definition were also used in defining DFS to facilitate comparison with other studies.
The target sample size was 50 patients. Allowing for a 15% ineligibility rate, the total sample size was 60 patients. Sample size determination was based on the late toxicity endpoint. A single-stage design was used to test the null hypothesis that the late unacceptable radiation toxicity probability at 2 years is P ≤ .05 versus the alternative hypothesis that toxicity probability at 2 years is P ≥ .15. Unacceptable toxicity was defined as grade 3 or higher toxicity, excluding sexual function. If at least 5 patients experienced late radiation toxicities at 2 years, the null hypothesis would be rejected. This design had a power of 89% and a type I error rate of 0.10. Acute and late toxicities at 2 years were estimated by proportions and 95% confidence intervals (CIs) based on the binomial distribution. The Kaplan-Meier product-limit method was used to estimate the DFS and OS distributions.
As part of the quality assurance program of the CALGB, members of the Audit Committee visit all participating institutions at least once every 3 years to review source documents. The auditors verify compliance with federal regulations and protocol requirements, including those pertaining to eligibility, treatment, adverse events, tumor response, and outcome in a sample of protocols at each institution. Such on-site review of medical records was performed for a subgroup of 29 patients (46%) of the 63 patients under this study.
Sixty-three patients were enrolled; 61 eligible patients with confirmed valid on-study forms were included in the analysis. The median follow-up time among living patients was 73 months (range, 0-96 months). A total of 83% of patients received brachytherapy with I125 and 17% with Pd103. Patient and tumor characteristics are shown in Table 1.
|Characteristic||All Patients, N=61|
|Age, ya||67 [49-82]|
|Gleason score of tumorb|
|Clinical T stage, n=59b|
Both acute and late toxicity were assessed. Acute grade 2 and 3 toxicity occurred in 25% (95% CI, 14%-35%) and 7% (95% CI, 0%-13%) of patients, respectively. Urinary frequency/urgency (18%), urinary retention (7%), and proctitis (diarrhea, bleeding, and/or pain) (7%) were the most commonly reported grade 2 toxicities. Acute grade 3 toxicity was limited to dysuria (3%), urinary frequency/urgency (2%), and thrombosis (2%). A complete list of grade ≥2 acute toxicities is shown in Table 2. Late grade 2 and 3 toxicity occurred in 20% (95% CI, 10%-30%) and 3% (95% CI, 0%-8%) of patients, respectively. The most common late grade 2 toxicities were urinary frequency/urgency (7%), urinary retention (5%), urinary incontinence (5%), and proctitis (diarrhea, bleeding, and/or pain) (5%). Late grade 3 toxicity was limited to the 2 patients who experienced grade 3 acute dysuria that persisted despite medications. In both cases the dysuria resolved with longer-term follow-up. In 1 case resolution occurred spontaneously, and in the second dysuria resolved after a course of antibiotic therapy. This patient was treated empirically with antibiotics for dysuria in the first few months after brachytherapy and because of persistent dysuria was re-treated with antibiotic therapy a year and a half after treatment. Notably, urinalysis was culture negative on both occasions. A complete list of grade ≥2 late toxicities is shown in Table 3.
|Nonhematologic Adverse Eventsa||Grade of Adverse Event||Total|
|Fatigue (asthenia, lethargy, malaise)||2||3||0||0||0||0||0||0||61|
|Dysuria (painful urination)||3||5||2||3||0||0||0||0||61|
|Urinary retention (including neurogenic bladder)||4||7||0||0||0||0||0||0||61|
|Maximum overall adverse events||15||25||4||7||0||0||0||0||61|
|AEs||Grade of AE||Total|
|Maximum hematologic AEs||1||2||0||0||0||0||0||0||61|
|RTOG/EORTC late radiation morbidity scoring scheme|
|Bladder, late RT morbidity scoring||1||2||0||0||0||0||0||0||61|
|Small/large intestine, late RT morbidity scoring||1||2||0||0||0||0||0||0||61|
|Fatigue (asthenia, lethargy, malaise)||2||3||0||0||0||0||0||0||61|
|Dysuria (painful urination)||0||0||2||3||0||0||0||0||61|
|Urinary retention (including neurogenic bladder)||3||5||0||0||0||0||0||0||61|
|Maximum overall AEs||12||20||2||3||0||0||0||0||61|
Six-year DFS applying the protocol definition, 1997 ASTRO consensus definition, and Phoenix definition of biochemical failure was 87.1%, 75.1%, and 84.9%, respectively, as shown in Figures 1 through 3. There were 6 deaths, only 1 of which was attributed to prostate cancer. The 6-year OS rate was 96.1%, as shown in Figure 4.
Although EBRT combined with LDR brachytherapy is a common approach to treatment of prostate cancer, only 2 phase 2 studies conducted by cooperative groups have been completed, including CALGB 99809. The other study, RTOG 0019, similar to CALGB 99809, was designed to assess toxicity, and participants were followed up to provide an initial assessment of treatment efficacy. RTOG 0019 included patients with clinical stage cT1c or T2a disease and either a Gleason score of 6 or lower and PSA levels of 10 to 20 ng/mL, or a Gleason score of 7 and PSA levels up to 20 ng/mL. All 138 patients were treated with EBRT to the prostate and seminal vesicles, which comprised 45 Gy 3-dimensional conformal EBRT, followed 2 to 6 weeks later by LDR brachytherapy boost with 108 Gy I125. Use of up to 6 months of ADT was left to the discretion of the treating physicians. Late genitourinary toxic effects were graded according to the CTC version 2.0, and all other toxic effects were evaluated according to the RTOG and European Organization for Research and Treatment of Cancer late radiation morbidity scoring system. In an initial report, median follow-up was 19 months, and acute grade 3 toxic events were documented in 7.6% of patients. No grade 4 or 5 acute toxic events or late grade 4 or 5 toxic events were observed.4 Increased toxicity was noted in a subsequent report with a median follow-up of 49 months, but was deemed acceptable. Grade 3 genitourinary and gastrointestinal side effects occurred in 10.8% and 3.1% of patients, respectively, and grade 4 genitourinary side effects occurred in 2% of patients. The rate of grade 3 or higher gastrointestinal and/or genitourinary toxic effects at 4 years was estimated to be 15%, which was higher than the estimate in RTOG series of EBRT or LDR brachytherapy alone. Biochemical recurrence was defined according to either the 1997 ASTRO consensus definition or the Phoenix definition. The estimated 4-year rate of freedom from biochemical recurrence according to the ASTRO and Phoenix criteria were 81% and 86%, respectively.5
To date, expectations for treatment outcomes have been primarily based on retrospective, single-institution analyses. Sylvester and coworkers reported long-term results on 223 patients who underwent EBRT to 45 Gy, the majority of whom received treatment to a limited pelvic field followed by brachytherapy boost with either I125 (108 Gy) or Pd103 (90 Gy). Biochemical recurrence was defined according to a modified ASTRO consensus criterion of 2 consecutive rises in PSA levels. With median follow-up of 9 years, applying the D'Amico and Memorial Sloan-Kettering Cancer Center risk stratification criteria, the 15-year rates of biochemical freedom from recurrence for patients at low risk in the Sylvester et al trial were 86% and 88%, for those at intermediate risk 80% and 80%, and for those at high risk 68% and 53%.6 Dattoli et al reported on patients with median follow-up of 9.5 years. Patients received a median dose of 41 Gy EBRT to a limited pelvic field up to the common iliac lymph nodes, followed by a brachytherapy boost with Pd103 (80-90 Gy).7 Biochemical failure was assessed per the 1997 ASTRO consensus definition, nadir + 2 definition, and absolute PSA >0.2 ng/mL at last follow-up. Actuarial rates of freedom from biochemical failure at 14 years were 87% for patients at intermediate risk and 72% for those at high risk without significant variance identified when applying the 3 definitions of biochemical failure. National Comprehensive Cancer Network guidelines were used for risk stratification (intermediate risk: T2b to T2c, or Gleason 7, or PSA 10-20 ng/mL; high-risk: T3a or Gleason 8-10, or PSA >20 mg/mL). Notably, the absolute risk of biochemical failure decreased progressively and fell to <1% after 6 years. Other researchers have reported similarly favorable findings in studies with shorter follow-up.8-11
There are 3 phase 3 trials inclusive of men with intermediate disease contemporary with CALGB 99809 assessing external beam with or without ADT. A trial from the Dana-Farber Cancer Institute included 206 patients with cT1b-cT2b disease (American Joint Committee on Cancer [AJCC] fourth edition criteria) with PSA ≥10 and ≤40 ng/mL or PSA ≥7 ng/mL treated with 70 Gy ± 6 months of total ADT. With median follow-up of 4.5 years, a survival benefit was noted for patients receiving ADT, with 5-year OS of 88% with no deaths because of prostate cancer. Survival without salvage ADT was 82% at 5 years for patients receiving ADT.12 An update with median follow-up of 7.6 years reported estimated 8-year OS of 74% with prostate cancer-specific mortality of 3% for patients on the ADT arm of the trial.13 The Trans-Tasman Group reported results on 818 men with cT2b-cT4 disease (AJCC fourth edition criteria) randomized to 66 Gy alone or with either 3 or 6 months of ADT. Only 18% of patients, however, were defined as intermediate risk. For patients receiving 6 months of ADT, 5-year disease-specific survival, freedom from salvage treatment, and prostate cancer-specific survival were 52%, 78%, and 94%, respectively.14 Preliminary results of RTOG 9408 were reported in 2009; 1979 men were enrolled, including 1068 patients with intermediate-risk disease, defined as Gleason score 7 or Gleason of 6 or less and either a PSA of 10 to 20 or T2b disease. Patients received 66.6 Gy ± 4 months of ADT. Eight-year OS with versus without ADT was 72% versus 66%, which was statistically significant.15
A challenge in evaluating efficacy of combined modality therapy inclusive of ADT is the potential for misinterpretation of PSA rise because of testosterone rebound after cessation of ADT with biochemical failure. Distinguishing benign rise in PSA from biochemical recurrence is further complicated by the well-documented phenomenon of PSA bounce after brachytherapy.16-18 The 1997 ASTRO consensus definition of biochemical failure has been shown to overestimate biochemical failure for patients who are treated with either ADT or brachytherapy when longer-term analyses allowing for subsequent decline in PSA are performed.19, 20 To address this concern, the protocol definition of PSA failure, 3 consecutive PSA rises >1.0 ng/mL after 18 months from start of treatment, was developed and applied in the analysis. Subsequently, the Phoenix definition, nadir + 2, was found to have improved accuracy in defining biochemical failure.20 To facilitate comparisons with past and future studies, both the 1997 ASTRO consensus definition and the Phoenix definition were assessed along with the protocol definition. The finding of a lower rate of biochemical control in the current study using the 1997 ASTRO consensus definition in comparison with the other 2 definitions is therefore not unexpected. Ultimately, impact on survival is the most important assessment of efficacy, and only a phase 3 trial will satisfactorily assess survival.
Treatment efficacy is important; however, the impact of any treatment on disease control or eradication has to be considered in the larger context of toxicity and quality of life. Given that prostate cancer presents without significant symptoms for most men with clinically localized disease, and that survival is typically protracted, treatment-related toxicity is an important factor to be considered in choosing an approach to disease management. The long-term rates of grade 2 and 3 toxicity in the current study compare well to the other completed co-operative group study.5 We previously reported on the primary study endpoint, rate of grade ≥3 toxicity with 39 months median follow-up.21 Now with nearly double the median follow-up time only a modest increase in toxicity was noted, and only in the grade 2 category, with an increase from 13% in our initial report to 21% in this report. It is noted that median time to late genitourinary and gastrointestinal toxicity is approximately 18 months.22-25 Therefore, with 73 months median follow-up we believe it is very unlikely that significantly more toxicity will manifest with further follow-up. It is also important to recognize that intensity-modulated radiation therapy (IMRT) was not allowed on CALGB 99809, as guidelines for use of IMRT in cooperative group trials had yet to be developed at the time of study inception. The use of IMRT and improved brachytherapy techniques has potential to further reduce toxicity.
The excellent results of CALGB 99809 in terms of both DFS and toxicity are notable; however, there are several limitations of the study that should be recognized. Enrolling institutions all had experience with the use of transperineal prostate brachytherapy, as there was a requirement that each participating site have a minimum of 50 prior cases to accrue patients for this study. Implant quality was excellent as assessed on central review with a median V90 of 98%, and only 1 implant did not meet the minimum study criteria for V90 of 80%. Therefore, the results may not be applicable to centers with less prostate brachytherapy experience. The study also required the use of ADT. Although ADT has been shown to improve OS in 3 randomized studies of intermediate-risk patients treated with EBRT,12, 14, 15 no randomized studies investigating the use of hormonal therapy have been performed for patients undergoing brachytherapy. Given the modest doses of EBRT used in these trials, 1 hypothesis is that with dose escalation currently in common use, ADT will not be necessary. A new RTOG study, RTOG 0815, has been designed to address this question. Given the potential side effects of ADT, combined EBRT and brachytherapy may be a more attractive therapeutic approach if ADT could be omitted. Impotence is a common concern for patients contemplating treatment for prostate cancer. Use of ADT coupled with lack of utilization of a validated instrument to assess sexual function made assessment of the impact of combined EBRT with brachytherapy boost difficult in the present study. The total number of patients is also modest albeit sufficient to address the primary study objective. Also, the favorable efficacy findings would be strengthened by confirmatory findings of other multi-institutional studies such as RTOG 0815 and RTOG 0232, the latter of which is designed to compare brachytherapy alone versus EBRT with brachytherapy boost for patients with intermediate-risk disease. Results from both of these studies will not be available for many years; however, the current study provides valuable insight into results achievable with combined modality therapy across a broad range of institutions.
In a cooperative setting, combination of EBRT and transperineal prostate brachytherapy boost with 6 months of ADT resulted in excellent DFS with acceptable acute and late toxicity for patients with intermediate-risk prostate cancer. Enrollment of intermediate-risk patients into phase 3 trials assessing EBRT combined with transperineal prostate brachytherapy boost should be encouraged.
This work was supported, in part, by grants from the National Cancer Institute (CA31946) to the Cancer and Leukemia Group B (Monica M. Bertagnolli, MD, Chair) and to the CALGB Statistical Center (Stephen George, PhD, CA33601). M.D.H. was supported by CA32291. S.H. and L.A. were supported by CA33601. L.S.M. was supported by CA45808. M.R.K. was supported by CA59518. E.J.S. was supported by CA60138. The content of this article is solely the responsibility of the authors and does not necessarily represent the official views of the National Cancer Institute.
The following institutions participated in this study: Christiana Care Health Services, Inc. Community Clinical Oncology Program, Wilmington, Delaware—Stephen Grubbs, MD, supported by CA45418; Dana-Farber Cancer Institute, Boston, Massachusetts—Harold J. Burstein, MD, PhD, supported by CA32291; Duke University Medical Center, Durham, North Carolina—Jeffrey Crawford, MD, supported by CA47577; Missouri Baptist Medical Center, St Louis, Missouri—Alan P. Lyss, MD, supported by CA114558-02; Nevada Cancer Research Foundation Community Clinical Oncology Program, Las Vegas, Nevada—John A. Ellerton, MD, supported by CA35421; Roswell Park Cancer Institute, Buffalo, New York—Ellis Levine, MD, supported by CA59518; Southeast Cancer Control Consortium Inc. Community Clinical Oncology Program, Goldsboro, North Carolina—James N. Atkins, MD, supported by CA45808; State University of New York Upstate Medical University, Syracuse, New York—Stephen L. Graziano, MD, supported by CA21060; University of Maryland Greenebaum Cancer Center, Baltimore, Maryland—Martin Edelman, MD, supported by CA31983; University of Massachusetts Medical School, Worcester, Massachusetts—William V. Walsh, MD, supported by CA37135; University of Missouri/Ellis Fischel Cancer Center, Columbia, Missouri—Michael C Perry, MD, supported by CA12046; University of North Carolina at Chapel Hill, Chapel Hill, North Carolina—Thomas C. Shea, MD, supported by CA47559; University of Vermont, Burlington, Vermont—Steven M. Grunberg, MD, supported by CA77406; and Wake Forest University School of Medicine, Winston-Salem, North Carolina—David D Hurd, MD, supported by CA03927.
CONFLICT OF INTEREST DISCLOSURES
The authors made no disclosures.
- 1103Pd brachytherapy and external beam irradiation for clinically localized, high-risk prostate carcinoma. Int J Radiat Oncol Biol Phys. 1997; 39: 776-777., , , et al.
- 5Late toxicity and biochemical recurrence after external-beam radiotherapy combined with permanent-source prostate brachytherapy: analysis of Radiation Therapy Oncology Group study 0019. Cancer. 2007; 109: 1506-1512., , , et al.
- 15Short term androgen deprivation prior to and during radiation therapy improves overall survival in patients with t1b-t2b adenocarcinoma of the prostate and PSA ≤20: initial results of RTOG 94-08 [abstract]. ASTRO 2009., , , et al.