Updated results of magnetic resonance imaging guided partial prostate brachytherapy for favorable risk prostate cancer: implications for focal therapy

Focal brachytherapy as definitive treatment for localized prostate cancer: A systematic review and meta-analysis

PURPOSE

In this systematic review and meta-analysis, we describe the oncologic and toxicity outcomes of definitive focal brachytherapy for prostate cancer.

METHODS AND MATERIALS

A PROSPERO registered study (CRD42023410170) was conducted following the Preferred Reporting Items for Systematic reviews and Meta-analyses (PRISMA) guidelines. PubMed, Embase, and The Cochrane Library were searched for studies between 2000 and 2022. Two authors independently performed the initial search. Biochemical recurrence-free survival (bRFS) was defined as the primary endpoint for the meta-analysis. Generalized linear mixed-effects models were conducted to calculate effect size and quantify heterogeneity. We also describe the side effects and local recurrence patterns of focal brachytherapy.

RESULTS

Ten studies were identified and included 315 patients treated using focal brachytherapy as a definitive treatment. Mean (SD) age was 67.65 (7.9) years and mean (SD) PSA was 7.15 (2.7) ng/mL. Most patients (n = 236, 75%) underwent LDR Brachytherapy and 25% received HDR brachytherapy. Among the participants, 147 (46.5%) had a Gleason score ≤6, and 169 (53.5%) had a Gleason score ≥7. Only 11 (3.5%) patients received ADT. Overall, bRFS rate at median follow-up 4 years (Range: 1-6.42 years) was 91% (95% confidence interval [CI], 82-95%). Acute Grade ≤ 2 GU and GI toxicities were reported in 22 (7%) and 11 (3.5%) patients, respectively. Late Grade ≤ 2 GU and GI toxicity were reported in 6 (2%) and 14 (4.4%) patients, respectively. One case of prostate hemorrhage due to improper foley removal was noted but otherwise no acute or late Grade 3 or higher GI or GU toxicity related to radiotherapy was reported.

CONCLUSION

Overall, definitive focal brachytherapy has a favorable toxicity profile. Oncologic outcomes are yet to mature. The evidence is limited by the small number of studies with low patients' number, across study heterogeneity, and possibility of publication bias.

Review of brachytherapy clinical trials: a cross-sectional analysis of ClinicalTrials.gov

INTRODUCTION

Characterizing the landscape of clinical trials including brachytherapy can provide an overview of the current status and research trends which may guide further areas of investigation.

METHOD

We queried 449,849 clinical trials from the ClinicalTrials.gov registry using brachytherapy-related keywords from 1980 to 2023, yielding 245 multi-arm and 201 single-arm, brachytherapy trials. Multi-arm and single-arm brachytherapy trials were compared using 12 trial protocol elements.

RESULTS

The number of trials including brachytherapy has increased over time, with over 60% of trials registered in 2010 onwards. The majority of clinical trials were Phase 2 or 3, evaluated both safety and efficacy, and were funded by academic sponsors. The most common tumor sites evaluated in brachytherapy clinical trials include prostate, cervix, liver, endometrium, and breast.

CONCLUSION

There remains continued interest in clinical trials including brachytherapy focused on evaluation of novel delivery systems, treatment planning, and new indications. More brachytherapy clinical trials are needed to define the optimal clinical utilization and advance prospective research in this field.

Oncological results and cancer control definition in focal therapy for Prostate Cancer: a systematic review

INTRODUCTION

Focal therapy (FT) is a promising alternative to whole-gland treatments for Localized Prostate Cancer. Ten different FT modalities have been described in literature. However, FT is not yet recommended by the International Guidelines, due to the lack of robust data on Oncological Outcomes. The objective of our Narrative Review is to evaluate the oncological profile of the available FT modalities and to offer a comprehensive overview of the definitions of Cancer Control for FT.

MATERIAL AND METHODS

Literature search was performed on 21^st February 2023 using PubMed, EMBASE, and Scopus, following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement (PRISMA). Articles reporting whole gland-treatments were excluded. All articles reporting oncological outcomes were included.

RESULTS

One-hundred-twenty-four studies, reporting data on more than 8000 patients treated with FT, were included. Overall, 40 papers were on High Intensity Focal Ultrasound (HIFU), 24 on Focal Cryotherapy, 13 on Irreversible Electroporation (IRE), 11 on Focal brachytherapy, 10 on Focal Laser Ablation (FLA), 8 on Photo-Dynamic Therapy (PDT), 3 on Microwave ablation, 3 on Robotic Partial Prostatectomy, 2 on bipolar Radio Frequency Ablation (bRFA), 1 on Prostatic Artery Embolization (PAE) and 9 comparative papers. Overall, the Biochemical Recurrence (BCR) rate ranged from 0% (Focal Brachytherapy) to 67.5% (HIFU); the Salvage treatment rate ranged from 1% (IRE) to 54% (HIFU) considering re-treatment with FT and from 0% (Focal Brachytherapy) to 66.7% considering standard Radical Treatments. There is no univocal definition of Cancer Control, however the "Phoenix criteria" for BCR were the most commonly used.

CONCLUSIONS

FT is a promising alternative treatment for localized prostate cancer in terms of Oncological Outcomes, however there is a wide heterogeneity in the definition of cancer control, the reporting of oncological outcomes and a lack of high-quality clinical trials. Solid comparative studies with standard treatments and an unambiguous consensus on how to describe Cancer Control in the field of Focal Therapy are needed.

Data-driven adaptive needle insertion assist for transperineal prostate interventions

Objective.Clinical outcomes of transperineal prostate interventions, such as biopsy, thermal ablations, and brachytherapy, depend on accurate needle placement for effectiveness. However, the accurate placement of a long needle, typically 150-200 mm in length, is challenging due to needle deviation induced by needle-tissue interaction. While several approaches for needle trajectory correction have been studied, many of them do not translate well to practical applications due to the use of specialized needles not yet approved for clinical use, or to relying on needle-tissue models that need to be tailored to individual patients.Approach.In this paper, we present a robot-assisted collaborative needle insertion method that only requires an actuated passive needle guide and a conventional needle. The method is designed to assist a physician inserting a needle manually through a needle guide. If the needle is deviated from the intended path, actuators shifts the needle radially in order to steer the needle trajectory and compensate for needle deviation adaptively. The needle guide is controlled by a new data-driven algorithm which does not requirea prioriinformation about needle or tissue properties. The method was evaluated in experiments with bothin vitroandex vivophantoms.Main results.The experiments inex vivotissue reported a mean final placement error of 0.36 mm with a reduction of 96.25% of placement error when compared to insertions without the use of assistive correction.Significance.Presented results show that the proposed closed-loop formulation can be successfully used to correct needle deflection during collaborative manual insertion with potential to be easily translated into clinical application.

Feasibility of MRI targeted single fraction HDR brachytherapy for localized prostate carcinoma: ProFocAL-study

Purpose

A potential method for focal therapy in locally advanced prostate cancer is focal brachytherapy (F-BT). The purpose of this research was to evaluate midterm F-BT oncologic, functional, and toxicological results in men who had therapy for prostate cancer.

Materials and methods

Between 2016 and 2020, F-BT was used to treat 37 patients with low- to intermediate-risk prostate cancer. The recommended dosage was 20 Gy. Failure was defined as the existence of any prostate cancer that has persisted in-field after treatment. The F-BT oncologic and functional outcomes served as the main and secondary objectives, respectively.

Results

A median 20-month follow-up (range 14–48 months). 37 patients received F-BT and enrolled in the study; no patient experienced a biochemical recurrence in the first 24 months, according to Phoenix criteria. In the control biopsies, only 6 patients showed in-field failure. The median initial IPSS was 6.5, at 6 months was 6.0, and at 24 months was 5.0. When the median ICIQ-SF score was 0 at the baseline, it remained 0 at 6-, 12-, and 24 months. Overall survival and biochemical disease-free survival after 3 years were all at 100% and 86.4%, respectively. There was no notable acute gastro-intestinal (GI) or genitourinary (GU) adverse effects. No intraoperative or perioperative complications occurred.

Conclusions

For selected patients with low- or intermediate-risk localized prostate cancer, F-BT is a safe and effective therapy.

Focal Prostate Stereotactic Body Radiation Therapy With Correlative Pathological and Radiographic-Based Treatment Planning

Introduction

Advances in multiparametric MRI (mpMRI) combining anatomic and functional imaging can accurately identify foci of adenocarcinoma within the prostate, offering the possibility of partial gland therapy. We performed tandem prospective pilot trials to investigate the feasibility of focal prostate SBRT (f-SBRT) based on correlating diagnostic mpMRI and biopsies with confirmatory pathology in treatment planning.

Materials and Methods

Patients with pathologic focal Gleason 6–7 disease and a corresponding PIRADS 4–5 lesion on mpMRI underwent targeted and comprehensive biopsies using MRI/ultrasound fusion under electromagnetic sensor navigation. After rigorous analysis for imaging biopsy concordance, five of 18 patients were eligible to proceed to f-SBRT. Chi-squared test was used for differences from expected outcomes, and concordance was estimated with binomial distribution theory and Wilson’s method.

Results

Six patients had Gleason 6 and 12 had Gleason 3 + 4 disease (mean PSA: 5.8 ng/ml, range: 2.2–8.4). Absolute concordance was 43.8% (95% CI: 0.20, 0.64). Patterns of discordance included additional sites of ipsilateral disease, bilateral disease, and negative target. Five were upstaged to a new NCCN risk category necessitating treatment escalation. The five patients with concordant pathology completed three-fraction f-SBRT with sparing of the surrounding normal structures (including contralateral neurovascular bundle), with no reported grade 2+ toxicities and favorable PSA responses (mean: 41% decrease).

Conclusions

On our pilot trials of f-SBRT planning using rigorous imaging and pathology concordance, image-guided confirmatory biopsies frequently revealed additional disease, suggesting the need for caution in partial-gland therapy. For truly focal disease, f-SBRT provided excellent dosimetry, minimal toxicity, and encouraging biochemical response. Clinical Trial Registration: www.clinicaltrials.gov, NCT02681614; NCT02163317.

Integration of functional imaging in brachytherapy

Functional imaging allows the evaluation of numerous biological properties that could be considered at all steps of the therapeutic management of patients treated with brachytherapy. Indeed, it enables better initial staging of the disease, and some parameters may also be used as predictive biomarkers for treatment response, allowing better selection of patients eligible for brachytherapy. It may also improve the definition of target volumes with the aim of dose escalations by dose-painting. Finally, it could be useful during the follow-up to assess response to treatment. In this review, we report how functional imaging is integrated at the present time during the brachytherapy procedure, and what are its potential future contributions in the main tumour locations where brachytherapy is recommended. Functional imaging has great potential in the contact of brachytherapy, but still, several issues remain to be resolved before integrating it into clinical practice, especially as a biomarker or in dose painting strategies.

Focal Brachytherapy for Localized Prostate Cancer: Midterm Outcomes

PURPOSE

Focal brachytherapy (F-BT) is a suitable technique for focal therapy in localized prostate cancer. It has the ability to adapt the seed implantation to the volume and location of the tumor. The aim of this study was to assess F-BT oncologic, functional, and toxicity midterm outcomes in men who underwent prostate cancer treatment.

METHODS AND MATERIALS

The study included 39 men with low- to intermediate-risk prostate cancer treated with F-BT between 2010 and 2015. The dose prescription was 145 Gy. Failure was defined as the presence of any residual prostate cancer in the treated area. The primary and secondary endpoints were the F-BT oncologic and functional outcomes, respectively. A 2-sided P value < .05 indicated statistical significance.

RESULTS

The mean follow-up time was 65 months (range, 43-104 months). After 24 months, 34 patients underwent control biopsies and 5 patients refused. The biopsies were negative in 27 cases (79%) and positive in 7 cases (21%), all outside the volume treated. Biochemical relapse-free survival at 5 years, disease-free survival, and overall survival were 96.8% ± 0.032%, 79.5% ± 0.076%, and 100%, respectively. The mean International Prostate Symptom Score at 2 months was significantly higher than initially (P = .0003), with no significant difference later. No late urinary, sexual, or rectal toxicity was observed. Salvage treatment was possible with good tolerance at 3.4 years of follow-up. Limitations of this study include the retrospective nature and lack of randomization.

CONCLUSIONS

F-BT is a safe and effective treatment for selected patients presenting with low- or intermediate-risk localized prostate cancer.

Voxel-based comparison of [68Ga]Ga-RM2-PET/CT and [68Ga]Ga-PSMA-11-PET/CT with histopathology for diagnosis of primary prostate cancer

BACKGROUND

Focal therapies or focally escalated therapies of primary prostate cancer are becoming more and more important. This increases the need to identify the exact extension of the intraprostatic tumor and possible dominant intraprostatic lesions by imaging techniques. While the prostate-specific membrane antigen (PSMA) is already a well-established target for imaging of prostate cancer cells, the gastrin-releasing peptide receptor (GRPR) seems to provide interesting additional information. Histopathology was used to examine the extent to which the single and combined image information of PET scans targeting GRPR and PSMA might lead to better tumor delineation.

METHODS

Eight patients with histologically proven primary prostate cancer underwent two positron emission tomography with computer tomography scans, [68Ga]Ga-RM2-PET/CT (RM2-PET) and [68Ga]Ga-PSMA-11-PET/CT (PSMA-PET), prior to radical prostatectomy. RM2-PET data were correlated voxel-wise to a voxel-based model of the histopathologic tumor volume information. The results were compared to, correlated to, and combined with the correlation of PSMA-PET data analyzed analogously.

RESULTS

In 4/8 patients, RM2-PET showed a higher signal in histologically proven tumor regions compared to PSMA. There were also tumor regions where PSMA-PET showed a higher signal than GRPR in 4/8 patients. A voxel-wise correlation of RM2-PET against histopathology yielded similar results compared to the correlation of PSMA-PET against histopathology, while PSMA-PET is the slightly better performing imaging technique. The combined information of both tracers yielded the best overall result, although this effect was not statistically significant compared to RM2-PET alone.

CONCLUSIONS

Qualitative and quantitative findings in this preliminary study with 8 patients indicate that RM2-PET and PSMA-PET partially show not only the same, but also distinct regions of prostate cancer. Patients with pPCa might profit from information given by tracers targeting GRPR and PSMA simultaneously, in terms of a better delineation of the gross tumor volume.

Targeting the cancer lesion, not the whole prostate

Modern cancer treatment aims to conserve as much healthy tissue as possible. This has been challenging in the treatment of prostate cancer due to the difficulty in imaging the gland and concerns over leaving multifocal cancer untreated. With improvements in imaging and understanding of multifocal prostate cancer evidence now shows accurate treatment of just the primary focus of cancer or the index lesion can control progression or recurrence of the disease. Many different energy sources are now available to target the cancer lesion within the prostate with less significant side-effects on urinary and sexual function compared to radical treatment. Evidence shows that men value these functions highly and would even trade years of life in exchange for preserved retention of continence or erectile function. Focal treatment of prostate cancer aims to provide both cancer control and preservation of sexual and urinary functions so that men do not have to make a choice between the two. This is a treatment option that men clearly want and deserve.

Focal therapy for localized prostate cancer in the era of routine multi-parametric MRI

BACKGROUND

Prostate cancer focal therapy aims to minimize the side-effects of whole gland treatments, such as radical prostatectomy and radiotherapy without compromising oncological efficacy. However, concerns exist regarding the multifocal nature of prostate cancer and the lack of long-term oncological data for this form of treatment. In recent years, the routine adoption of multi-parametric magnetic resonance imaging (mpMRI) of the prostate has improved our ability to select candidates for focal therapy and to accurately deliver this form of prostate cancer treatment.

METHODS

We performed a review of the literature to provide a summary of the oncological and functional outcomes of men receiving primary prostate focal therapy. Furthermore, we discuss the impact of the routine implementation of mpMRI as part of the initial prostate cancer diagnostic pathway on the selection of candidates and delivery of focal therapy. Finally, we summarize knowledge gaps in the field and highlight active clinical trials in this arena.

RESULTS

Primary focal therapy involves the application of one of a number of energies that ablate tissue, such as cryotherapy and high intensity focused ultrasound (HIFU). Success is principally dependent on highly accurate patient selection and disease localization underpinned in large part by the routine integration of pre-biopsy mpMRI. Prospective medium-term follow-up data for primary HIFU and cryotherapy for men with intermediate-risk disease have shown acceptable cancer control with low risk of side effects and complications. Additional research is needed to clearly define an appropriate follow-up approach and to guide the management of in- and out-of-field recurrences. Multiple comparative trials with randomization against standard care are currently underway in men with intermediate- and high-risk prostate cancer.

CONCLUSION

The widespread adoption of prostate mpMRI has led to improved disease localization, enabling the performance of focal therapy as a viable treatment strategy for men with low volume intermediate-risk prostate cancer.

Extensive disease among potential candidates for hemi-ablative focal therapy for prostate cancer

OBJECTIVE

To examine a set of proposed eligibility factors for hemi-ablative focal therapy in prostate cancer and to determine the likelihood of residual extensive disease.

METHODS

We retrospectively analyzed data from 98 patients with unilateral prostate cancer on biopsy with detailed tumor maps from whole-mount slides and preoperative magnetic resonance imaging data. These patients met the focal therapy consensus meeting inclusion criteria (prostate-specific antigen <15 ng/mL, clinical stage T1c-T2a and Gleason score 3 + 3 or 3 + 4 on needle biopsy), and underwent radical prostatectomy between 2000 and 2014. Extensive disease was defined as having Gleason pattern 4/5 in bilateral lobes, any extraprostatic extension, seminal vesicle invasion or lymph node invasion. Both lobes of the prostate were scored on magnetic resonance imaging. Preoperative characteristics including biopsy and magnetic resonance imaging data were used to predict extensive disease.

RESULTS

Among our cohort of 98 patients, 40% (95% CI 30-50%) had extensive disease. A total of 33% (95% CI 24-43%) had Gleason pattern 4/5 in both lobes with a median Gleason pattern 4/5 tumor volume in the biopsy negative lobe of 0.06 cm³ , 17 patients had pathological tumor stage ≥3 and one patient had lymph node invasion.

CONCLUSIONS

An important number of patients meeting the focal therapy consensus meeting inclusion criteria can present extensive disease. Further studies using targeted biopsies might provide more accurate information about the selection of focal therapy candidates.

Individual lymph nodes: "See it and Zap it"

BACKGROUND AND PURPOSE

With magnetic resonance imaging (MRI)-guided radiotherapy systems such as the 1.5T MR-linac the daily anatomy can be visualized before, during and after radiation delivery. With these treatment systems, seeing metastatic nodes with MRI and zapping them with stereotactic body radiotherapy (SBRT) comes into reach. The purpose of this study is to investigate different online treatment planning strategies and to determine the planning target volume (PTV) margin needed for adequate target coverage when treating lymph node oligometastases with SBRT on the 1.5T MR-linac.

MATERIALS AND METHODS

Ten patients were treated for single pelvic or para-aortic lymph node metastases on the 1.5T MR-linac with a prescribed dose of 5x7Gy with a 3 mm isotropic GTV- PTV margin. Based on the daily MRI and actual contours, a completely new treatment plan was generated for each session (adapt to shape, ATS). These were compared with plans optimized on pre-treatment CT contours after correcting for the online target position (adapt to position, ATP). At the end of each treatment session, a post-radiation delivery MRI was acquired on which the GTV was delineated to evaluate the GTV coverage and PTV margins.

RESULTS

The median PTV V35Gy was 99.9% [90.7-100%] for the clinically delivered ATS plans compared to 93.6% [76.3-99.7%] when using ATP. The median GTV V35Gy during radiotherapy delivery was 100% [98-100%] on the online planning and post-delivery MRIs for ATS and 100% [93.9-100%] for ATP, respectively. The applied 3 mm isotropic PTV margin is considered adequate.

CONCLUSION

For pelvic and para-aortic metastatic lymph nodes, online MRI-guided adaptive treatment planning results in adequate PTV and GTV coverage when taking the actual patient anatomy into account (ATS). Generally, GTV coverage remained adequate throughout the treatment session for both adaptive planning strategies. "Seeing and zapping" metastatic lymph nodes comes within reach for MRI-guided SBRT.

MRI-Guided Ultrafocal HDR Brachytherapy for Localized Prostate Cancer: Median 4-Year Results of a feasibility study

PURPOSE

For the treatment of localized prostate cancer, focal therapy has the potential to cure with fewer side effects than traditional whole-gland treatments. We report an update on toxicity, quality of life (QoL), and tumor control in our magnetic resonance imaging (MRI)-guided ultrafocal high-dose-rate brachytherapy cohort.

METHODS AND MATERIALS

Disease status was evaluated by systematic biopsies and 3T multiparametric MRI. The brachytherapy implant procedure under fused transrectal ultrasound/MRI guidance was followed by a 1.5 T MRI for contour adjustments and catheter position verification. A single dose of 19 Gy was delivered to the tumor with a margin of 5 mm. Genitourinary (GU) toxicity, gastrointestinal (GI) toxicity, and erectile dysfunction (ED) were graded with the Common Terminology Criteria for Adverse Events version 4.0. QoL was measured with RAND-36, European Organisation for Research and Treatment of Cancer QLQ-C30 and PR25. International Prostate Symptom Scores and International Index of Erectile Function scores were obtained. Prostate-specific antigen level was monitored, with biochemical recurrence defined as nadir + 2 ng/mL (Phoenix).

RESULTS

Thirty patients with National Comprehensive Cancer Network low- (13%) to intermediate-risk (87%) prostate cancer were treated between May 2013 and April 2016. Median follow-up was 4 years. Median age was 71 years (interquartile range, 68-73) and median initial prostate-specific antigen level was 7.3 ng/mL (5.2-8.1). Maximum Gleason score was 4 + 3 = 7 (in 2 patients). All tumors were radiologic (MRI) stage T2. No grade >2 GU or >1 GI toxicity occurred. International Prostate Symptom Scores only deteriorated temporarily. Mild pretreatment ED deteriorated to moderate/severe ED in 50% of patients. Long-term clinically relevant QoL deterioration was seen in sexual activity and tiredness, whereas emotional and cognitive functioning improved. At 4 years, biochemical disease-free survival was 70% (95% confidence interval, 52%-93%), metastases-free survival was 93% (85%-100%), and overall survival was 100%. Of intraprostatic recurrences, 7 of 9 were out of field.

CONCLUSIONS

Ultrafocal high-dose-rate brachytherapy conveys minimal GU or GI toxicity and has a marginal effect on QoL. An early decline in erectile function was seen. Tumor control outcomes are poor (biochemical disease-free survival of 70% [52%-93%] at 4 years), most likely as a result of poor patient selection.

Focal therapy for localized prostate cancer: is there a "middle ground" between active surveillance and definitive treatment?

In recent years, it has come a long way in the diagnosis, treatment, and follow-up of prostate cancer. Beside this, it was argued that definitive treatments could cause overtreatment, particularly in the very low, low, and favorable risk group. When alternative treatment and follow-up methods are being considered for this group of patients, active surveillance is seen as a good alternative for patients with very low and low-risk groups in this era. However, it has become necessary to find other alternatives for patients in the favorable risk group or patients who cannot adopt active follow-up. In the light of technological developments, the concept of focal therapy was introduced with the intensification of research to treat only the lesioned area instead of treating the entire organ for prostate lesions though there are not many publications about many of them yet. According to the initial results, it was understood that the results could be good if the appropriate focal therapy technique was applied to the appropriate patient. Thus, focal therapies have begun to find their "middle ground" place between definitive therapies and active follow-up.

MRI guided focal HDR brachytherapy for localized prostate cancer: Toxicity, biochemical outcome and quality of life

PURPOSE

To describe toxicity, biochemical outcome and quality of life after MRI guided focal high dose rate brachytherapy (HDR-BT) in a single fraction of 19 Gy for localized prostate cancer.

MATERIALS AND METHODS

Between May 2013 and April 2016, 30 patients were treated by MRI-guided focal HDR-BT. Patients with visible tumour on MRI were included. All patients were ≥65 years, T-stage <T3, Gleason ≤7, PSA <10 ng/mL and IPSS <15. Focal irradiation was delivered in a single fraction of 19 Gy to the D95 of the clinical target volume. Toxicity was reported using the Common Terminology Criteria for Adverse Events version 4. Biochemical failure was defined according to the Phoenix criteria and quality of life was measured using validated questionnaires.

RESULTS

Median follow up was 24 months. One patient developed a grade 2 and 3 GU toxicity after treatment. In the other 29 patients, no grade 2 or higher perioperative complications occurred. Five patients developed a biochemical recurrence. For all measured time points, there was no statistically significant deterioration in quality of life.

CONCLUSION

Focal MRI guided HDR-BT confers low toxicity rates and maintains quality of life. Biochemical recurrence is rather high, 5 patients developed a biochemical recurrence according to the Phoenix definition. Longer evaluation of these patients is necessary and caution is warranted before implementing focal HDR-BT in patients with localized prostate cancer.

Long-term outcomes of partial prostate treatment with magnetic resonance imaging-guided brachytherapy for patients with favorable-risk prostate cancer

BACKGROUND

Partial prostate treatment has emerged as a potential method for treating patients with favorable-risk prostate cancer while minimizing toxicity. The authors previously demonstrated poor rates of biochemical disease control for patients with National Comprehensive Cancer Network (NCCN) intermediate-risk disease using partial gland treatment with brachytherapy. The objective of the current study was to estimate the rates of distant metastasis and prostate cancer-specific mortality (PCSM) for this cohort.

METHODS

Between 1997 and 2007, a total of 354 men with clinical T1c disease, a prostate-specific antigen (PSA) level < 15 ng/mL, and Gleason grade ≤3 + 4 prostate cancer underwent partial prostate treatment with brachytherapy to the peripheral zone under 0.5-Tesla magnetic resonance guidance. The cumulative incidences of metastasis and PCSM for the NCCN very low-risk, low-risk, and intermediate-risk groups were estimated. Fine and Gray competing risk regression was used to evaluate clinical factors associated with time to metastasis.

RESULTS

A total of 22 patients developed metastases at a median of 11.0 years (interquartile range, 6.9-13.9 years). The 12-year metastasis rates for patients with very low-risk, low-risk, and intermediate-risk disease were 0.8% (95% confidence interval [95% CI], 0.1%-4.4%), 8.7% (95% CI, 3.4%-17.2%), and 15.7% (95% CI, 5.7%-30.2%), respectively, and the 12-year PCSM estimates were 1.6% (95% CI, 0.1%-7.6%), 1.4% (95% CI, 0.1%-6.8%), and 8.2% (95% CI, 1.9%-20.7%), respectively. On multivariate analysis, NCCN risk category (low risk: hazard ratio, 6.34 [95% CI, 1.18-34.06; P = .03] and intermediate risk: hazard ratio, 6.98 [95% CI, 1.23-39.73; P = .03]) was found to be significantly associated with the time to metastasis.

CONCLUSIONS

Partial prostate treatment with brachytherapy may be associated with higher rates of distant metastasis and PCSM for patients with intermediate-risk disease after long-term follow-up. Treatment of less than the full gland may not be appropriate for this cohort.

[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.

The prostate cancer focal therapy

Despite prostate cancer (PCa) is the leading form of non-cutaneous cancer in men, most patients with PCa die with disease rather than of the disease. Therefore, the risk of overtreatment should be considered by clinicians who have to distinguish between patients with high risk PCa (who would benefit from radical treatment) and patients who may be managed more conservatively, such as through active surveillance or emerging focal therapy (FT). The aim of FT is to eradicate clinically significant disease while protecting key genito-urinary structures and function from injury. While effectiveness studies comparing FT with conventional care options are still lacking, the rationale supporting FT relies on evidence-based advances such as the understanding of the index lesion's central role in the natural history of the PCa and the improvement of multiparametric magnetic resonance imaging (mpMRI) in the detection and risk stratification of PCa. In this literature review, we want to highlight the rationale for FT in PCa management and the current evidence on patient eligibility. Furthermore, we summarize the best imaging modalities to localize the target lesion, describe the current FT techniques in PCa, provide an update on their oncological outcomes and highlight trends for future research.

IDEAL 2a Phase II Study of Ultrafocal Brachytherapy for Low- and Intermediate-risk Prostate Cancer

PURPOSE

Focal therapy of prostate cancer requires precise positioning of therapeutic agents within well-characterized index tumors (ITs). We assessed the feasibility of low-dose-rate ultrafocal brachytherapy.

METHODS AND MATERIALS

The present study was an institutional review board-approved European Clinical Trials Database-registered phase II protocol. Patients referred (October 2013 to August 2016) for active surveillance (prostate-specific antigen <10 ng/mL, cT1c-cT2a, Gleason score on referring biopsy specimens ≤6 (3+3), ≤3 positive biopsy cores, ≤50% of cancer) were preselected. Inclusion was confirmed when complementary image-guided biopsy findings informed a single Prostate Imaging Reporting and Data System (PI-RADS) ≥3, Gleason score ≤7a (3+4) lesion. A ultrasound-visible ancillary marker was positioned within the IT using a magnetic resonance imaging (MRI)/3-dimensional transrectal ultrasound (TRUS) elastic fusion-guided system (Koelis). Ultrafocal transperineal delivery of ¹²⁵I seeds used classic 2-dimensional TRUS (Bard-FlexFocus) and dose optimization (Variseed Treatment Planning System). Following Simon's optimal design, 17 patients were required to assess the feasibility of delivering ≥95% of the prescribed dose (160 Gy) to the IT (primary objective). Adverse events (Common Terminology Criteria for Adverse Events) and quality of life (5-item International Index of Erectile Function, International Prostate Symptom Score) were recorded. One-year control biopsy specimens were obtained from the IT and untreated segments.

RESULTS

Of the 44 preselected patients, 27 did not meet the inclusion criteria. Of the 17 ultrafocal brachytherapy-treated patients, 16 met the primary objective (per protocol success). The prescription dose was delivered to 14.5% ± 6.4% of the prostate volume, resulting in negligible urethral and rectal irradiation and toxicity. No recurrence was evidenced on the 1-year follow-up MRI studies or IT biopsy specimens. Seven nonclinically significant cancers and one Gleason score 7a (3+4) cancer (salvage prostatectomy) were observed in the untreated parenchyma.

CONCLUSIONS

Recent technology has allowed for selective and effective brachytherapy of small MRI targets.

Focal Therapy in Primary Localised Prostate Cancer: The European Association of Urology Position in 2018

Radical treatment of localised prostate cancer is recognised to be an unnecessary intervention or overtreatment in many men. Consequently, there has been a rapid uptake in the use of focal ablative therapies. However, there are several biological and practical concerns about such approaches as they have yet to be proved as robust treatment options. In particular, the multifocal nature of prostate cancer argues against unifocal treatment, while limitations in imaging can preclude the accurate identification of the number, location, and extent of prostate cancer foci. To date, a number of ablative options have reported results on mainly low-risk disease. Most series are relatively immature, with a lack of consistent follow-up, and the morbidity of retreatment is often not considered. The authors consider focal therapy to be an investigational modality, and encourage prospective recording of outcomes and recruitment of suitable patients.

PATIENT SUMMARY

Focal therapy of prostate cancer is the targeted destruction of cancer within a specific part of the prostate gland, sparing the rest of the prostate and nearby tissue. This procedure could potentially reduce side effects when compared with established standard treatments, such as surgery or radiotherapy, which treat the entire prostate. Studies show that for most men with low-risk cancer, active surveillance is the preferred treatment option. However, the available data regarding all forms of focal therapy are still poor and inconclusive. Consequently, due to both the lack of clear results associated with focal therapy and the difficulties in detecting all cancerous areas of the prostate, focal therapy should be considered an investigational modality only.

Focal therapy for prostate cancer: the technical challenges

Focal therapy for prostate cancer has been proposed as an alternative treatment to whole gland therapy, offering the opportunity for tumor dose escalation and/or reduced toxicity. Brachytherapy, either low-dose-rate or high-dose-rate, provides an ideal approach, offering both precision in dose delivery and opportunity for a highly conformal, non-uniform dose distribution. Whilst multiple consensus documents have published clinical guidelines for patient selection, there are insufficient data to provide clear guidelines on target volume delineation, treatment planning margins, treatment planning approaches, and many other technical issues that should be considered before implementing a focal brachytherapy program. Without consensus guidelines, there is the potential for a diversity of practices to develop, leading to challenges in interpreting outcome data from multiple centers. This article provides an overview of the technical considerations for the implementation of a clinical service, and discusses related topics that should be considered in the design of clinical trials to ensure precise and accurate methods are applied for focal brachytherapy treatments.

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.

Magnetic resonance imaging-guided functional anatomy approach to prostate brachytherapy

PURPOSE

To provide an MRI based functional anatomy guide to prostate brachytherapy.

METHODS AND MATERIALS

We performed a narrative review of periprostatic functional anatomy and the significance of this anatomy in prostate brachytherapy treatment planning.

RESULTS

MRI has improved delineation of gross tumor and critical periprostatic structures that have been implicated in toxicity. Furthermore, MRI has revealed the significant anatomic variants and the dynamic nature of these structures that can have significant implications for treatment planning and dosimetry.

CONCLUSIONS

The MRI-based functional anatomy approach to prostate brachytherapy takes into account extent of disease, its relation to the patient's individual anatomy, and functional baseline to optimize the therapeutic ratio of prostate cancer treatment.

Dosimetric feasibility of ablative dose escalated focal monotherapy with MRI-guided high-dose-rate (HDR) brachytherapy for prostate cancer

PURPOSE

To determine the dosimetric feasibility of dose-escalated MRI-guided high-dose-rate brachytherapy (HDR-BT) focal monotherapy for prostate cancer (PCa).

METHODS

In all patients, GTV was defined with mpMRI, and deformably registered onto post-catheter insertion planning MRI. PTV included the GTV plus 9mm craniocaudal and 5mm in every other direction. In discovery-cohort, plans were obtained for each PTV independently aiming to deliver ⩾16.5Gy/fraction (two fraction schedule) while respecting predefined organs-at-risk (OAR) constraints or halted when achieved equivalent single-dose plan (24Gy). Dosimetric results of original and focal HDR-BT plans were evaluated to develop a planning protocol for the validation-cohort.

RESULTS

In discovery-cohort (20-patients, 32-GTVs): PTV D95% ⩾16.5Gy could not be reached in a single plan (3%) and was accomplished (range 16.5-23.8Gy) in 15 GTVs (47%). Single-dose schedule was feasible in 16 (50%) plans. In the validation-cohort (10-patients, 10-GTVs, two separate implants each): plans met acceptable and ideal criteria in 100% and 43-100% respectively. Migration to single-dose treatment schedule was feasible in 7 implants (35%), without relaxing OAR's constraints or increasing the dose (D100% and D35%) to mpMRI-normal prostate (p>0.05).

CONCLUSION

Focal ablative dose-escalated radiation is feasible with the proposed protocol. Prospective studies are warranted to determine the clinical outcomes.

Focal therapy as primary treatment for localized prostate cancer: definition, needs and future

Focal therapy (FT) may offer a promising treatment option in the field of low to intermediate risk localized prostate cancer. The aim of this concept is to combine minimal morbidity with cancer control as well as maintain the possibility of retreatment. Recent advances in MRI and targeted biopsy has improved the diagnostic pathway of prostate cancer and increased the interest in FT. However, before implementation of FT in routine clinical practice, several challenges are still to overcome including patient selection, treatment planning, post-therapy monitoring and definition of oncologic outcome surrogates. In this article, relevant questions regarding the key steps of FT are critically discussed and the main available energy modalities are analyzed taking into account their advantages and unmet needs.

Outcomes and toxicities in patients treated with definitive focal therapy for primary prostate cancer: systematic review

AIM

This systematic review summarizes the clinical data on focal therapy (FT) when used alone as definitive therapy for primary prostate cancer (PCa).

METHODS

The protocol is detailed in the online PROSPERO database, registration No. CRD42014014765. Articles evaluating any form of FT alone as a definitive treatment for PCa in adult male patients were included.

RESULTS

Of 10,419 identified articles, 10,401 were excluded, and thus leaving 18 for analysis. In total, 2288 patients were treated using seven modalities. The outcomes of FT in PCa seem to be similar to those observed with whole gland therapy and with fewer side effects.

CONCLUSION

Further research, including prospective randomized trials, is warranted to elucidate the potential advantages of focal radiation techniques for treating PCa. Prospero Registration Number: CRD42014014765.

MRI-guided focal laser ablation for prostate cancer followed by radical prostatectomy: correlation of treatment effects with imaging

Purpose

To correlate treatment effects of MRI-guided focal laser ablation in patients with prostate cancer with imaging using prostatectomy as standard of reference.

Methods

This phase I study was approved by the Institutional Review Board. Three weeks prior to prostatectomy, five patients with histopathologically proven, low/intermediate grade prostate cancer underwent transrectal MRI-guided focal laser ablation. Per patient, only one ablation was performed to investigate the effect of ablation on the tissue rather than the effectiveness of ablation. Ablation was continuously monitored with real-time MR temperature mapping, and damage-estimation maps were computed. A post-ablation high-resolution T1-weighted contrast-enhanced sequence was acquired. Ablation volumes were contoured and measured on histopathology specimens (with a shrinkage factor of 1.15), T1-weighted contrast-enhanced images, and damage-estimation maps, and were compared.

Results

A significant volume correlation was seen between the ablation zone on T1-weighted contrast-enhanced images and the whole-mount histopathology section (r = 0.94, p = 0.018). The damage-estimation maps and histopathology specimen showed a correlation of r = 0.33 (p = 0.583). On histopathology, the homogeneous necrotic area was surrounded by a reactive transition zone (1–5 mm) zone, showing neovascularisation, and an increased mitotic index, indicating increased tumor activity.

Conclusions

The actual ablation zone was better indicated by T1-weighted contrast-enhanced than by damage-estimation maps. Histopathology results highlight the importance of complete tumor ablation with a safety margin.

(68)Ga-HBED-CC-PSMA PET/CT Versus Histopathology in Primary Localized Prostate Cancer: A Voxel-Wise Comparison

Purpose: We performed a voxel-wise comparison of ⁶⁸Ga-HBED-CC-PSMA PET/CT with prostate histopathology to evaluate the performance of ⁶⁸Ga-HBED-CC-PSMA for the detection and delineation of primary prostate cancer (PCa).

Methodology: Nine patients with histopathological proven primary PCa underwent ⁶⁸Ga-HBED-CC-PSMA PET/CT followed by radical prostatectomy. Resected prostates were scanned by ex-vivo CT in a special localizer and histopathologically prepared. Histopathological information was matched to ex-vivo CT. PCa volume (PCa-histo) and non-PCa tissue in the prostate (NPCa-histo) were processed to obtain a PCa-model, which was adjusted to PET-resolution (histo-PET). Each histo-PET was coregistered to in-vivo PSMA-PET/CT data.

Results: Analysis of spatial overlap between histo-PET and PSMA PET revealed highly significant correlations (p < 10^-5) in nine patients and moderate to high coefficients of determination (R²) from 42 to 82 % with an average of 60 ± 14 % in eight patients (in one patient R² = 7 %). Mean SUVmean in PCa-histo and NPCa-histo was 5.6 ± 6.1 and 3.3 ± 2.5 (p = 0.012). Voxel-wise receiver-operating characteristic (ROC) analyses comparing the prediction by PSMA-PET with the non-smoothed tumor distribution from histopathology yielded an average area under the curve of 0.83 ± 0.12. Absolute and relative SUV (normalized to SUVmax) thresholds for achieving at least 90 % sensitivity were 3.19 ± 3.35 and 0.28 ± 0.09, respectively.

Conclusions: Voxel-wise analyses revealed good correlations of ⁶⁸Ga-HBED-CC-PSMA PET/CT and histopathology in eight out of nine patients. Thus, PSMA-PET allows a reliable detection and delineation of PCa as basis for PET-guided focal therapies.

Hemiablative Focal Low Dose Rate Brachytherapy: A Phase II Trial Protocol

BACKGROUND

The objective of focal brachytherapy (BT) is to provide effective prostate cancer control for low-risk disease but with reduced genitourinary, gastrointestinal and sexual side effects in a cost-effective way.

OBJECTIVE

The aim of this study is to describe a phase II study examining technical and dosimetric feasibility and toxicity, quality of life changes, and local control with post-treatment biopsy outcomes in men with early stage low volume prostate cancer treated with focal iodine-125 seed BT.

METHODS

The study design is a prospective, multicenter trial with a planned sample size of 20 patients including men with a minimum age of 60 years, a life expectancy estimated to be greater than 10 years, with low or low-tier intermediate risk prostate cancer, unilateral disease on the biopsy, and a Gleason score of ≤3+4 and <25% cores involved. The investigations specific for the study are multi-parametric magnetic resonance imaging (Mp-MRI) baseline, at 20 and 36 months to rule out high grade disease and a transperineal mapping biopsy (baseline and at 36 months) for more accurate patient selection. The hemigland region will receive 144 Gy. Standard normal tissue constraints will be considered as for a whole gland (WG) implant. Dosimetric parameters will be evaluated at day 30 after the implant. Toxicity and quality of life will be evaluated with international validated questionnaires focusing on urinary, rectal, sexual domain, and general health-related quality of life. The patients will complete this assessment at baseline and then approximately every 6 months after the implant up to 10 years.

RESULTS

To date, one patient is involved in the trial. He underwent the pre-implant investigations which found bilateral disease. Therefore, a standard seed implant was performed. If the results from this trial provide evidence that the treatment is safe, feasible, and improves toxicity, funding will be sought to conduct a large, multicenter, randomized controlled trial (RCT).

CONCLUSIONS

This protocol is designed to show feasibility in delivering hemigland focal therapy with seed BT. It may answer crucial questions and obtain data which will enable downstream decisions on focal low dose rate (LDR) prostate BT.

CLINICALTRIAL

Clinicaltrial.gov NCT02643511; https://www.clinicaltrials.gov/ct2/show/NCT02643511 (Archived by Webcite at http://www.webcitation.org/6ghLCzIhY).

Evolving Paradigm of Radiotherapy for High-Risk Prostate Cancer: Current Consensus and Continuing Controversies

High-risk prostate cancer is an aggressive form of the disease with an increased risk of distant metastasis and subsequent mortality. Multiple randomized trials have established that the combination of radiation therapy and long-term androgen deprivation therapy improves overall survival compared to either treatment alone. Standard of care for men with high-risk prostate cancer in the modern setting is dose-escalated radiotherapy along with 2-3 years of androgen deprivation therapy (ADT). There are research efforts directed towards assessing the efficacy of shorter ADT duration. Current research has been focused on assessing hypofractionated and stereotactic body radiation therapy (SBRT) techniques. Ongoing randomized trials will help assess the utility of pelvic lymph node irradiation. Research is also focused on multimodality therapy with addition of a brachytherapy boost to external beam radiation to help improve outcomes in men with high-risk prostate cancer.

Standardization of definitions in focal therapy of prostate cancer: report from a Delphi consensus project

PURPOSE

To reach standardized terminology in focal therapy (FT) for prostate cancer (PCa).

METHODS

A four-stage modified Delphi consensus project was undertaken among a panel of international experts in the field of FT for PCa. Data on terminology in FT was collected from the panel by three rounds of online questionnaires. During a face-to-face meeting on June 21, 2015, attended by 38 experts, all data from the online rounds were reviewed and recommendations for definitions were formulated.

RESULTS

Consensus was attained on 23 of 27 topics; Targeted FT was defined as a lesion-based treatment strategy, treating all identified significant cancer foci; FT was generically defined as an anatomy-based (zonal) treatment strategy. Treatment failure due to the ablative energy inadequately destroying treated tissue is defined as ablation failure. In targeting failure the energy is not adequately applied to the tumor spatially and selection failure occurs when a patient was wrongfully selected for FT. No definition of biochemical recurrence can be recommended based on the current data. Important definitions for outcome measures are potency (minimum IIEF-5 score of 21), incontinence (new need for pads or leakage) and deterioration in urinary function (increase in IPSS >5 points). No agreement on the best quality of life tool was established, but UCLA-EPIC and EORTC-QLQ-30 were most commonly supported by the experts. A complete overview of statements is presented in the text.

CONCLUSION

Focal therapy is an emerging field of PCa therapeutics. Standardization of definitions helps to create comparable research results and facilitate clear communication in clinical practice.

In-bore MRI interventions: current status and future applications

PURPOSE OF REVIEW

This review discusses the feasibility, recent advances and current status of in-bore MRI-guided interventional techniques for diagnosis and treatment of focal prostate cancer (PCa) and also explores the future applications, highlighting the emerging strategies for the treatment of PCa.

RECENT FINDINGS

Multiparametric MRI has opened up opportunities for diagnosis and targeted therapeutics to the site of disease within the organ wherein minimizing the incidence of treatment-related toxicity of whole gland therapy. MRI-guided targeted biopsy has a higher detection rate for significant cancer and lower rate of detection of insignificant cancer. In comparison to ultrasound-guided focal therapy, in-bore treatment provides the advantage of real time thermal monitoring during treatment and assessment of treatment coverage by an enhanced scan immediately post-treatment. Preliminary results of ongoing phase I and II in-bore focal PCa treatment trials via transperineal, transrectal and transurethral routes, using different energy modalities for the ablation, have shown promising results.

SUMMARY

Advances in multiparametric-MRI has opened up opportunities for in-bore targeted focal treatment of PCa in the correctly selected patient.

Prostate Radiotherapy in the Era of Advanced Imaging and Precision Medicine

Tremendous technological advancements in prostate radiotherapy have decreased treatment toxicity and improved clinical outcomes for men with prostate cancer. While these advances have allowed for significant treatment volume reduction and whole-organ dose escalation, further improvement in prostate radiotherapy has been limited by classic techniques for diagnosis and risk stratification. Developments in prostate imaging, image-guided targeted biopsy, next-generation gene expression profiling, and targeted molecular therapies now provide information to stratify patients and select treatments based on tumor biology. Image-guided targeted biopsy improves detection of clinically significant cases of prostate cancer and provides important information about the biological behavior of intraprostatic lesions which can further guide treatment decisions. We review the evolution of prostate magnetic resonance imaging (MRI) and MRI-ultrasound fusion-guided prostate biopsy. Recent advancements in radiation therapy including dose escalation, moderate and extreme hypofractionation, partial prostate radiation therapy, and finally dose escalation by simultaneous integrated boost are discussed. We also review next-generation sequencing and discuss developments in targeted molecular therapies. Last, we review ongoing clinical trials and future treatment paradigms that integrate targeted biopsy, molecular profiling and therapy, and prostate radiotherapy.

Dosimetric benefits of hemigland stereotactic body radiotherapy for prostate cancer: implications for focal therapy

OBJECTIVE

Compared with standard, whole-gland (WG) therapies for prostate cancer, focal approaches may provide equivalent oncologic outcomes with fewer adverse effects. The purpose of this study was to compare organ-at-risk (OAR) dosimetry between hemigland (HG) and WG stereotactic body radiotherapy (SBRT) plans.

METHODS

Volumetric-modulated arc radiotherapy-based SBRT plans were designed to treat the left HG, right HG and WG in eight patients, using five fractions of 8 Gy. OARs of interest included the contralateral HG, rectum, urinary bladder, urethra, penile bulb and contralateral neurovascular bundle.

RESULTS

Rectal V80% (the percentage of a normal structure receiving a dose of 80%) and V90% were significantly lower with HG plans than with WG plans (median values of 4.4 vs 2.5 cm(3) and 2.1 vs 1.1 cm(3), respectively, p < 0.05 by Student's t-test). Bladder V50% was also reduced significantly in HG plans (32.3 vs 17.4 cm(3), p < 0.05), with a trend towards reduction of V100% (3.4 vs 1.3 cm(3), p = 0.09). Urethral maximum dose and mean doses to the penile bulb and contralateral neurovascular bundle were also reduced significantly (42.0 vs 39.7 Gy, p < 0.00001; 13.3 vs 9.2 Gy, p < 0.05; and 40.2 vs 19.3 Gy, p < 0.00001, respectively).

CONCLUSION

Targeting an HG volume rather than a WG volume when delivering SBRT can offer statistically significant reductions for all OARs. Given the large magnitude of the reduction in dose to these OARs, it is anticipated that HG SBRT could offer a superior toxicity profile when compared with WG SBRT. This is likely to be most relevant in the context of salvaging a local failure after radiation therapy.

ADVANCES IN KNOWLEDGE

The dosimetric feasibility of HG SBRT is demonstrated. When compared with WG SBRT plans, the HG plans demonstrate statistically significant and large magnitude reduction in doses to the rectum, bladder, urethra, penile bulb and contralateral neurovascular bundle, suggesting the possibility of improved toxicity outcomes with HG SBRT. This is likely to be most relevant in the context of salvaging a local failure after radiation therapy.

Dysuria Following Stereotactic Body Radiation Therapy for Prostate Cancer

Background

Dysuria following prostate radiation therapy is a common toxicity that adversely affects patients’ quality of life and may be difficult to manage.

Methods

Two hundred four patients treated with stereotactic body radiation therapy (SBRT) from 2007 to 2010 for localized prostate carcinoma with a minimum follow-up of 3 years were included in this retrospective review of prospectively collected data. All patients were treated to 35–36.25 Gy in five fractions delivered with robotic SBRT with real time fiducial tracking. Dysuria and other lower urinary tract symptoms were assessed via Question 4b (Pain or burning on urination) of the expanded prostate index composite-26 and the American Urological Association (AUA) Symptom Score at baseline and at routine follow-up.

Results

Two hundred four patients (82 low-, 105 intermediate-, and 17 high-risk according to the D’Amico classification) at a median age of 69 years (range 48–91) received SBRT for their localized prostate cancer with a median follow-up of 47 months. Bother associated with dysuria significantly increased from a baseline of 12% to a maximum of 43% at 1 month (p < 0.0001). There were two distinct peaks of moderate to severe dysuria bother at 1 month and at 6–12 months, with 9% of patients experiencing a late transient dysuria flare. While a low level of dysuria was seen through the first 2 years of follow-up, it returned to below baseline by 2 years (p = 0.91). The median baseline AUA score of 7.5 significantly increased to 11 at 1 month (p < 0.0001) and returned to 7 at 3 months (p = 0.54). Patients with dysuria had a statistically higher AUA score at baseline and at all follow-ups up to 30 months. Dysuria significantly correlated with dose and AUA score on multivariate analysis. Frequency and strain significantly correlated with dysuria on stepwise multivariate analysis.

Conclusion

The rate and severity of dysuria following SBRT is comparable to patients treated with other radiation modalities.

Dosimetry Modeling for Focal Low-Dose-Rate Prostate Brachytherapy

PURPOSE

Focal brachytherapy targeted to an individual lesion(s) within the prostate may reduce side effects experienced with whole-gland brachytherapy. The outcomes of a consensus meeting on focal prostate brachytherapy were used to investigate optimal dosimetry of focal low-dose-rate (LDR) prostate brachytherapy targeted using multiparametric magnetic resonance imaging (mp-MRI) and transperineal template prostate mapping (TPM) biopsy, including the effects of random and systematic seed displacements and interseed attenuation (ISA).

METHODS AND MATERIALS

Nine patients were selected according to clinical characteristics and concordance of TPM and mp-MRI. Retrospectively, 3 treatment plans were analyzed for each case: whole-gland (WG), hemi-gland (hemi), and ultra-focal (UF) plans, with 145-Gy prescription dose and identical dose constraints for each plan. Plan robustness to seed displacement and ISA were assessed using Monte Carlo simulations.

RESULTS

WG plans used a mean 28 needles and 81 seeds, hemi plans used 17 needles and 56 seeds, and UF plans used 12 needles and 25 seeds. Mean D90 (minimum dose received by 90% of the target) and V100 (percentage of the target that receives 100% dose) values were 181.3 Gy and 99.8% for the prostate in WG plans, 195.7 Gy and 97.8% for the hemi-prostate in hemi plans, and 218.3 Gy and 99.8% for the focal target in UF plans. Mean urethra D10 was 205.9 Gy, 191.4 Gy, and 92.4 Gy in WG, hemi, and UF plans, respectively. Mean rectum D2 cm(3) was 107.5 Gy, 77.0 Gy, and 42.7 Gy in WG, hemi, and UF plans, respectively. Focal plans were more sensitive to seed displacement errors: random shifts with a standard deviation of 4 mm reduced mean target D90 by 14.0%, 20.5%, and 32.0% for WG, hemi, and UF plans, respectively. ISA has a similar impact on dose-volume histogram parameters for all plan types.

CONCLUSIONS

Treatment planning for focal LDR brachytherapy is feasible. Dose constraints are easily met with a notable reduction to organs at risk. Treating smaller targets makes seed positioning more critical.