Endorectal magnetic resonance imaging for predicting pathologic T3 disease in Gleason score 7 prostate cancer: implications for prostate brachytherapy

Target Volume Optimization for Localized Prostate Cancer

PURPOSE

To provide a comprehensive review of the means by which to optimize target volume definition for the purposes of treatment planning for patients with intact prostate cancer with a specific emphasis on focal boost volume definition.

METHODS

Here we conduct a narrative review of the available literature summarizing the current state of knowledge on optimizing target volume definition for the treatment of localized prostate cancer.

RESULTS

Historically, the treatment of prostate cancer included a uniform prescription dose administered to the entire prostate with or without coverage of all or part of the seminal vesicles. The development of prostate magnetic resonance imaging (MRI) and positron emission tomography (PET) using prostate-specific radiotracers has ushered in an era in which radiation oncologists are able to localize and focally dose-escalate high-risk volumes in the prostate gland. Recent phase 3 data has demonstrated that incorporating focal dose escalation to high-risk subvolumes of the prostate improves biochemical control without significantly increasing toxicity. Still, several fundamental questions remain regarding the optimal target volume definition and prescription strategy to implement this technique. Given the remaining uncertainty, a knowledge of the pathological correlates of radiographic findings and the anatomic patterns of tumor spread may help inform clinical judgement for the definition of clinical target volumes.

CONCLUSION

Advanced imaging has the ability to improve outcomes for patients with prostate cancer in multiple ways, including by enabling focal dose escalation to high-risk subvolumes. However, many questions remain regarding the optimal target volume definition and prescription strategy to implement this practice, and key knowledge gaps remain. A detailed understanding of the pathological correlates of radiographic findings and the patterns of local tumor spread may help inform clinical judgement for target volume definition given the current state of uncertainty.

AAPM Task Group Report 303 endorsed by the ABS: MRI Implementation in HDR Brachytherapy-Considerations from Simulation to Treatment

The Task Group (TG) on Magnetic Resonance Imaging (MRI) Implementation in High Dose Rate (HDR) Brachytherapy - Considerations from Simulation to Treatment, TG 303, was constituted by the American Association of Physicists in Medicine's (AAPM's) Science Council under the direction of the Therapy Physics Committee, the Brachytherapy Subcommittee, and the Working Group on Brachytherapy Clinical Applications. The TG was charged with developing recommendations for commissioning, clinical implementation, and on-going quality assurance (QA). Additionally, the TG was charged with describing HDR brachytherapy (BT) workflows and evaluating practical consideration that arise when implementing MR imaging. For brevity, the report is focused on the treatment of gynecologic and prostate cancer. The TG report provides an introduction and rationale for MRI implementation in BT, a review of previous publications on topics including available applicators, clinical trials, previously published BT related TG reports, and new image guided recommendations beyond CT based practices. The report describes MRI protocols and methodologies, including recommendations for the clinical implementation and logical considerations for MR imaging for HDR BT. Given the evolution from prescriptive to risk-based QA,¹ an example of a risk-based analysis using MRI-based, prostate HDR BT is presented. In summary, the TG report is intended to provide clear and comprehensive guidelines and recommendations for commissioning, clinical implementation, and QA for MRI-based HDR BT that may be utilized by the medical physics community to streamline this process. This report is endorsed by the American Brachytherapy Society (ABS). This article is protected by copyright. All rights reserved.

[Prostate brachytherapy: New techniques, new indications]

Prostate brachytherapy has been for a long time one of the standard treatments for low risk prostate cancer, with high rates of biochemical control and low levels of urinary and sexual late toxicity compared to other available techniques, namely external beam radiotherapy and radical prostatectomy. The aim of this article is to review the recent innovations of prostate brachytherapy, which suggest a bright future for the technique. We will discuss the extension of indications of permanent implant brachytherapy to favorable intermediate-risk patients, the use of novel isotopes such as Palladium 103 and Cesium 131, and the benefit of brachytherapy as a boost following external beam radiotherapy for intermediate and high-risk patients. We will also discuss the rise of high dose rate brachytherapy, as a boost or monotherapy, the increasing use of MRI for patient selection and treatment planning, as well as the development of brachytherapy as a means of focal therapy.

Low dose rate prostate brachytherapy

Low dose rate (LDR) prostate brachytherapy is an evidence based radiation technique with excellent oncologic outcomes. By utilizing direct image guidance for radioactive source placement, LDR brachytherapy provides superior radiation dose escalation and conformality compared to external beam radiation therapy (EBRT). With this level of precision, late grade 3 or 4 genitourinary or gastrointestinal toxicity rates are typically between 1% and 4%. Furthermore, when performed as a same day surgical procedure, this technique provides a cost effective and convenient strategy. A large body of literature with robust follow-up has led multiple expert consensus groups to endorse the use of LDR brachytherapy as an appropriate management option for all risk groups of non-metastatic prostate cancer. LDR brachytherapy is often effective when delivered as a monotherapy, although for some patients with intermediate or high-risk disease, optimal outcome are achieved in combination with supplemental EBRT and/or androgen deprivation therapy (ADT). In addition to reviewing technical aspects and reported clinical outcomes of LDR prostate brachytherapy, this article will focus on the considerations related to appropriate patient selection and other aspects of its use in the treatment of prostate cancer.

Lack of Benefit From the Addition of External Beam Radiation Therapy to Brachytherapy for Intermediate- and High-risk Prostate Cancer

PURPOSE

A recent randomized controlled trial demonstrated that the addition of external beam radiation therapy (EBRT) to brachytherapy did not improve progression-free survival in select patients with intermediate-risk prostate cancer. We evaluated whether the addition of EBRT to brachytherapy improves prostate cancer-specific mortality (PCSM) for intermediate- and high-risk disease using a large national database.

METHODS AND MATERIALS

We identified 5836 patients in the Surveillance, Epidemiology, and End Results-Medicare linked database with a diagnosis of National Comprehensive Cancer Network intermediate-risk (Gleason score 7, prostate-specific antigen 10-20 ng/mL, or stage cT2b-T2c) or high-risk (Gleason score 8-10 or prostate-specific antigen >20 ng/mL and stage ≤cT3a) prostate cancer who had undergone brachytherapy, with or without EBRT and androgen deprivation therapy (ADT). Patients were diagnosed from 2004 through 2009. Intermediate-risk patients with Gleason score ≤3+4 and 1 intermediate-risk factor were considered favorable and all others unfavorable. We used multivariable Fine-Gray competing risks regression to study PCSM while adjusting for sociodemographic and clinical factors and ADT use.

RESULTS

Overall, 50.3% of intermediate- and high-risk patients who received brachytherapy and EBRT did not have significantly improved PCSM compared with that of the patients who received brachytherapy alone (adjusted hazard ratio [AHR] 1.46, 95% confidence interval [CI] 0.69-3.11; P=.322; 5-year PCSM 2.4% vs 1.0%). This lack of benefit was seen among favorable intermediate-risk (AHR 2.66, 95% CI 0.93-7.62, P=.069; 5-year PCSM 1.3% vs 0.6%), unfavorable intermediate-risk (AHR 0.68, 95% CI 0.16-2.96, P=.612; 5-year PCSM 1.0% vs 1.2%), and high-risk (AHR 1.82, 95% CI 0.67-4.98, P=.242; 5-year PCSM 5.3% vs 2.1%) subgroups.

CONCLUSIONS

These results suggest that certain patients with intermediate- or high-risk prostate cancer treated with brachytherapy might not benefit from the addition of EBRT. A randomized controlled trial of brachytherapy plus ADT with or without EBRT for unfavorable intermediate- and favorable high-risk organ-confined prostate cancer should be undertaken.

Variability in Outcomes for Patients with Intermediate-risk Prostate Cancer (Gleason Score 7, International Society of Urological Pathology Gleason Group 2-3) and Implications for Risk Stratification: A Systematic Review

CONTEXT

Optimal management for patients with intermediate-risk (IR) prostate cancer (PCa) remains controversial. Clinical metrics provide guidance on appropriate management options.

OBJECTIVE

To report estimates for clinically relevant outcomes in men with IR PCa based on clinical and pathological features.

EVIDENCE ACQUISITION

PubMed and programs from key 2015 uro-oncology congresses were searched using the terms "intermediate", "Gleason 3 + 4", "Gleason 4 + 3", "active surveillance", "treatment", "adverse pathology", AND "prostate cancer." Articles meeting prespecified criteria were retrieved. Bibliographies were scanned for additional relevant references.

EVIDENCE SYNTHESIS

Men with IR PCa have a wide range of predicted clinically relevant outcomes. Within the IR category, estimate ranges for adverse surgical pathology and 5-yr disease progression are 15-64% and 21-91%, respectively. Clinical parameters and predictive nomograms refine these estimates, but do not uniformly differentiate favorable and unfavorable IR PCa. Variations in study design and data quality in source manuscripts mandate caution in interpreting results.

CONCLUSIONS

Outcomes in IR PCa are heterogeneous. Refinements in personalized risk assessment are needed to better select IR PCa patients for surveillance.

PATIENT SUMMARY

Current and future risk stratification tools may provide additional information to identify men with intermediate-risk prostate cancer who may consider active surveillance.

Magnetic resonance imaging in prostate brachytherapy: Evidence, clinical end points to data, and direction forward

The integration of multiparametric MRI into prostate brachytherapy has become a subject of interest over the past 2 decades. MRI directed high-dose-rate and low-dose-rate prostate brachytherapy offers the potential to improve treatment accuracy and standardize postprocedure quality. This article reviews the evidence to date on MRI utilization in prostate brachytherapy and postulates future pathways for MRI integration.

Clinical use of magnetic resonance imaging across the prostate brachytherapy workflow

MRI produces better soft tissue contrast than does ultrasonography or computed tomography for visualizing male pelvic anatomy and prostate cancer. Better visualization of the tumor and organs at risk could allow better conformation of the dose to the target volumes while at the same time minimizing the dose to critical structures and the associated toxicity. Although the use of MRI for prostate brachytherapy would theoretically result in an improved therapeutic ratio, its implementation been slow, mostly because of technical challenges. In this review, we describe the potential role of MRI at different steps in the treatment workflow for prostate brachytherapy: for patient selection, treatment planning, in the operating room, or for postimplant assessment. We further present the current clinical experience with MRI-guided prostate brachytherapy, both for permanent seed implantation and high-dose-rate brachytherapy.

ACR appropriateness criteria: Permanent source brachytherapy for prostate cancer

PURPOSE

To provide updated American College of Radiology (ACR) appropriateness criteria for transrectal ultrasound-guided transperineal interstitial permanent source brachytherapy.

METHODS AND MATERIALS

The ACR appropriateness criteria are evidence-based guidelines for specific clinical conditions that are reviewed every 3 years by a multidisciplinary expert panel. The guideline development and review include an extensive analysis of current medical literature from peer reviewed journals and the application of a well-established consensus methodology (modified Delphi) to rate the appropriateness of imaging and treatment procedures by the panel. In those instances where evidence is lacking or not definitive, expert opinion may be used to recommend imaging or treatment.

RESULTS

Permanent prostate brachytherapy (PPB) is a treatment option for appropriately selected patients with localized prostate cancer with low to very high risk disease. PPB monotherapy remains an appropriate and effective curative treatment for low-risk prostate cancer patients demonstrating excellent long-term cancer control and acceptable morbidity. PPB monotherapy can be considered for select intermediate-risk patients with multiparametric MRI useful in evaluation of such patients. High-risk patients treated with PPB should receive supplemental external beam radiotherapy (EBRT) along with androgen deprivation. Similarly, patients with involved pelvic lymph nodes may also be considered for such combined treatment but reported long-term outcomes are limited. Computed tomography-based postimplant dosimetry completed within 60 days of PPB is essential for quality assurance. PPB may be considered for treatment of local recurrence after EBRT but is associated with an increased risk of toxicity.

CONCLUSIONS

Updated appropriateness criteria for patient evaluation, selection, treatment, and postimplant dosimetry are given. These criteria are intended to be advisory only with the final responsibility for patient care residing with the treating clinicians.

Multiparametric magnetic resonance imaging for pre-treatment local staging of prostate cancer: A Cancer Care Ontario clinical practice guideline

INTRODUCTION

The utility of T2-weighted magnetic resonance imaging (MRI) in the local staging of prostate cancer is controversial. Due to the success of multiparametric MRI in cancer localization, there is renewed interested in MRI (± functional sequences) for local staging. Guidance on pre-treatment local staging of prostate cancer by MRI was developed using systematic review methodology and expert consultation.

METHODS

MEDLINE, EMBASE, Cochrane Database of Systematic Reviews, and other databases were searched to identify studies comparing: (1) MRI staging vs. radical prostatectomy staging on diagnostic accuracy outcomes; and (2) MRI staging vs. routine clinical staging on clinical and patient outcomes. Studies meeting inclusion criteria were synthesized by outcome and sensitivity/specificity analysis by tumour location was performed. Evidence quality of included studies was assessed and considered in recommendation formulation.

RESULTS

The literature search identified 2510 citations; 62 studies were included. Analysis of MRI ≥1.5 T plus endorectal coil (ER) (± functional sequences) in the detection of extraprostatic extension or seminal vesicle invasion showed modest sensitivities (≥50%) and excellent specificities (>85%) among patients scheduled for radical prostatectomy. MRI upstaging was shown in 20/21 studies, with large variation in correctness (11-85%). Scarcity of clinical and patient outcomes among studies limited synthesis and evaluation. Quality assessment found non-trivial biases.

CONCLUSIONS

Modest imaging performance was shown for MRI (1.5 T + ER and 3 T ± ER) ± functional sequences in regards to sensitivity. Limitations in study design, reporting of clinical and patient outcomes, and the heterogeneous use of MRI tempered the strength of the recommendations.

Advances in Prostate Cancer Magnetic Resonance Imaging and Positron Emission Tomography-Computed Tomography for Staging and Radiotherapy Treatment Planning

Conventional prostate cancer staging strategies have limited accuracy to define the location, grade, and burden of disease. Evaluations have historically relied upon prostate-specific antigen levels, digital rectal examinations, random systematic biopsies, computed tomography, pelvic lymphadenectomy, or ^99mtechnetium methylene diphosphonate bone scans. Today, risk-stratification tools incorporate these data in a weighted format to guide management. However, the limitations and potential consequences of their uncertainties are well known. Inaccurate information may contribute to understaging and undertreatment, or overstaging and overtreatment. Meanwhile, advances in multiparametric magnetic resonance imaging (MRI), whole-body MRI, lymphotropic nanoparticle-enhanced MRI, and positron emission tomography are now available to improve the accuracy of risk stratification to facilitate more informed medical decisions. They also guide radiation oncologists to develop more accurate treatment plans. This review provides a primer to incorporate these advances into routine clinical workflow.

Magnetic resonance image guided brachytherapy

The application of magnetic resonance image (MRI)-guided brachytherapy has demonstrated significant growth during the past 2 decades. Clinical improvements in cervix cancer outcomes have been linked to the application of repeated MRI for identification of residual tumor volumes during radiotherapy. This has changed clinical practice in the direction of individualized dose administration, and resulted in mounting evidence of improved clinical outcome regarding local control, overall survival as well as morbidity. MRI-guided prostate high-dose-rate and low-dose-rate brachytherapies have improved the accuracy of target and organs-at-risk delineation, and the potential exists for improved dose prescription and reporting for the prostate gland and organs at risk. Furthermore, MRI-guided prostate brachytherapy has significant potential to identify prostate subvolumes and dominant lesions to allow for dose administration reflecting the differential risk of recurrence. MRI-guided brachytherapy involves advanced imaging, target concepts, and dose planning. The key issue for safe dissemination and implementation of high-quality MRI-guided brachytherapy is establishment of qualified multidisciplinary teams and strategies for training and education.

Comparison between conventional imaging (abdominal-pelvic computed tomography and bone scan) and [(18)F]choline positron emission tomography/computed tomography imaging for the initial staging of patients with intermediate- tohigh-risk prostate cancer: A retrospective analysis

OBJECTIVE

The aim of this study was to evaluate the efficiency of [(18)F]fluorocholine positron emission tomography/computed tomography (FCH PET/CT) in detecting lymph-node and bone involvement in comparison with conventional imaging, such as abdominal-pelvic CT and bone scan, in the initial staging of prostate cancer (PCa).

MATERIALS AND METHODS

The study retrospectively evaluated 48 patients who had FCH PET/CT for the initial staging of PCa. At the same time, 32 of the 48 patients had a bone scan and 26 of the 48 patients had abdominal-pelvic diagnostic CT. Diagnostic performance of FCH PET/CT, i.e. sensitivity, specificity and accuracy, was evaluated on a per-patient basis for the whole population and then separately on a per-risk classification, and later in comparison with conventional imaging. Histological specimens or follow-up data were used as the standard of reference.

RESULTS

The overall accuracy of FCH PET/CT for lymph-node involvement was 83.3%. The sensitivity of FCH was higher in the high-risk subset (83.3%) than in the intermediate-risk group (33.3%), whereas FCH specificity was similar. In comparison with dedicated CT scan, FCH PET/CT showed a higher sensitivity and a similar specificity (46.2% vs 69.2% and 92.3% vs 92.3%, respectively). Moreover, the sensitivity and specificity of PET/CT were higher than those of bone scan (100% vs 90% and 86.4% vs 77.2%, respectively). In contrast with conventional imaging, PET/CT changed the staging of the PCa in 33.3% patients.

CONCLUSIONS

The efficiency of FCH PET/CT in detecting both bone and lymph-node involvement of PCa at initial staging was found to be higher than that of conventional imaging. Prospective clinical trials are needed to confirm these findings.