Focal Salvage High Dose-Rate Brachytherapy for Locally Recurrent Prostate Cancer After Primary Radiation Therapy Failure: Results From a Prospective Clinical Trial

Salvage reirradiation for locally recurrent prostate cancer: A narrative review

In this narrative review, we will explore the different options for salvage re-irradiation for locally recurrent prostate cancer. Brachytherapy (BT) and stereotactic body radiation therapy (SBRT) appear to be successful options. We detailed doses, volumes, oncological outcomes, and toxicity events to identify the best salvage strategy. Salvage reirradiation can only be proposed in certain cases, depending on the patient and the clinical scenario. Specific imaging and tests are needed to safely deliver this treatment.

Local salvage therapies in patients with radio-recurrent prostate cancer following external beam radiotherapy: a systematic review and meta-analysis

INTRODUCTION

To date, radio-recurrent prostate cancer (PCa) ranks as the fourth most common urological malignancy when considering the number of men with localized PCa who undergo radiation treatment and subsequently experience a biochemical recurrence. This systematic review aimed to summarize available evidence about the outcomes of local salvage strategies in patients with local PCa recurrence following primary external-beam radiation therapy (EBRT).

METHODS

We conducted a comprehensive bibliographic search on MEDLINE, Scopus, and Web of Science Core Collection databases in October 2023 to identify studies published in the last 20 years evaluating outcomes of local salvage procedures in patients with locally radio-recurrent PCa following EBRT. The meta-analysis was performed using ProMeta 3 software when two or more studies reported the same outcome. The effect size (ES) was estimated using rates reported with its 95% confidence interval (CI).

RESULTS

Overall, 28 studies (6 prospective and 22 retrospective) including 1544 patients were included in the review. Two-year recurrence-free survival (RFS) was 84.0% (95% CI: 67.0-93.0%), 69.0% (95% CI: 42.0-87.0%), 58.0% (95% CI: 43.0-71.0%), and 45% (95% CI: 38.0-52.0%), for patients undergoing brachytherapy (BT), EBRT, Cryotherapy and High-Intensity Focused Ultrasound (HIFU), respectively. After salvage prostatectomy, RFS ranged from 75% to 78.5% at a median follow-up ranging from 18 to 35 months. Estimates for severe gastrointestinal toxicity were 2%, 3%, 3%, 4%, and 11% following cryotherapy, BT, HIFU, EBRT, and salvage radical prostatectomy, respectively.

CONCLUSIONS

In patients who underwent EBRT as primary treatment, prostate salvage re-irradiation through BT or EBRT represents the modality providing the best balance between efficacy and safety. Unfortunately, due to the low level of evidence, strong recommendations regarding the choice of any of these techniques cannot be made.

Potentiating Salvage Radiotherapy in Radiorecurrent Prostate Cancer Through Anti-CTLA4 Therapy: Implications from a Syngeneic Model

High-risk prostate cancer (PCa) is a leading cause in cancer death and can elicit significant morbidity and mortality. Currently, the salvage of local disease recurrence after radiation therapy (RT) is a major clinical problem. Immune checkpoint inhibitors (ICIs), which enhance immune activation, have demonstrated clinical therapeutic promise in combination with ionizing radiation (IR) in certain advanced cancers. We generated the TRAMP-C2 HF radiorecurrent syngeneic mouse model to evaluate the therapeutic efficacy of ICIs in combination with RT. The administration of anti-PDL1 and/or anti-CTLA4 did not achieve a significant tumor growth delay compared to the control. The combination of IR and anti-PDL1 did not yield additional a growth delay compared to IR and the isotype control. Strikingly, a significant tumor growth delay and complete cure in one-third of the mice were seen with the combination of IR and anti-CTLA4. Immune cells in tumor-draining lymph nodes and tumor-infiltrating lymphocytes from mice treated with IR and anti-CTLA4 demonstrated an upregulation of genes in T-cell functions and enrichment in both CD4+ and CD8+ T-cell populations compared to mice given IR and the isotype control. Taken together, these results indicate enhancement of T-cell response in radiorecurrent PCa by IR and anti-CTLA4.

Safety of high-dose rate (HDR) brachytherapy for patients with prostate cancer and history of prior chemoradiation for rectal cancer: A case series

PURPOSE

A history of prior pelvic radiation therapy (RT) for rectal cancer is a relative contraindication for definitive RT for prostate cancer. High-dose-rate (HDR) brachytherapy can significantly limit the dose to surrounding tissues compared to external beam RT. However, there is limited data surrounding its safety in patients with prior pelvic RT.

METHODS AND MATERIALS

A retrospective chart review was performed at the University of California, San Francisco to identify patients diagnosed with prostate cancer with a history of pelvic RT for rectal cancer who were treated with high-dose-rate brachytherapy (HDR-BT) between 2006 and 2022. Inclusion criteria were biopsy-confirmed prostate cancer with no evidence of distant disease on clinical examination or imaging, and at least one post-treatment clinic appointment.

RESULTS

Seven patients were treated with salvage HDR-BT at a median interval of 17.7 years after RT for rectal cancer. HDR-BT doses included 3600 cGy in six fractions (n = 5), 2700 cGy in 2 fractions (n=1), or 2800 cGy in four fractions (n = 1). There was no acute grade ≥2 gastrointestinal toxicity, and 1 patient developed late grade 2 rectal bleeding. Two patients developed acute grade 2 genitourinary toxicity consisting of urinary frequency and urgency, which persisted through long-term follow up. At a median follow up of 29.5 months after HDR brachytherapy, one patient developed regional and distant failure, and another had seminal vesicle recurrence.

CONCLUSIONS

HDR-BT is a safe treatment for patients with prostate cancer who previously received RT for rectal cancer. Further studies are needed to better characterize the long-term toxicity of HDR-RT in this population.

US-guided EM tracked system for HDR brachytherapy: A first in-men randomized study for whole prostate treatment

PURPOSE

An electromagnetic tracking device (EMT) has been integrated in an HDR 3D ultrasound guidance system for prostate HDR. The aim of this study was to compare the efficiency of HDR workflows with and without EM tracking.

METHODS AND MATERIALS

A total of 58 patients with a 15 Gy HDR prostate boost were randomized in two arms and two operation room (OR) procedures using: (1) the EMT investigational device, and (2) the Oncentra prostate system (OCP). OR times were compared for both techniques.

RESULTS

The overall procedure median time was about 20% shorter for EMT (63 min) compared to OCP (79 min). The US acquisition and contouring was longer for OCP compared to EMT (23 min vs. 16 min). The catheter reconstruction's median times were 23 min and 13 min for OCP and EMT respectively. For the automatic reconstruction with EMT, 62% of cases required no or few manual corrections. Using the EM technology in an OR environment was challenging. In some cases, interferences or the stiffness of the stylet introduced errors in the reconstruction of catheters. The last step was the dosimetry with median times of 11 min (OCP) and 15.5 min (EMT). Finally, it was observed that there was no learning curve associated with the introduction of this new technology.

CONCLUSIONS

The EMT device offers an efficient solution for automatic catheter reconstruction for HDR prostate while reducing the possibility of mis-reconstructed catheters caused by issues of visualization in the US images. Because of that, the overall OR times was shorter when using the EMT system.

Recurrence characteristics after focal salvage HDR brachytherapy in prostate cancer

BACKGROUND AND PURPOSE

Radiorecurrent prostate cancer is often confined to the prostate, predominantly near the index lesion. The purpose of this study was to look at recurrence characteristics in patients treated with focal salvage high dose-rate (HDR) brachytherapy.

MATERIALS AND METHODS

Patients treated with MRI-guided HDR brachytherapy, with a single fraction of 19 Gy from July 2013 to October 2021 as focal salvage treatment, were prospectively included in the current study. Imaging data were collected regarding the occurrence of local, regional and distant recurrences, including location of local recurrences (LR) in relation to the HDR radiotherapy field.

RESULTS

One hundred seventy-five patients were included after focal salvage HDR brachytherapy (median follow-up 36 months (IQR 23-50)). Three-years biochemical recurrence-free survival, LR-free survival, in-field LR-free survival, out-of-field LR-free survival, any-recurrence-free survival and ADT-free survival were 43% (95%CI 34%-52%), 51% (41%-61%), 70% (61%-80%), 92% (88%-97%), 42% (32%-52%) and 86% (80%-92%), respectively. Larger GTV-size and shorter PSA doubling time were associated with in-field LR in multivariable analysis.

CONCLUSION

After focal salvage HDR brachytherapy with a dose of 1x19 Gy for local prostate cancer recurrence, subsequent recurrences are mostly local and in-field.

Reirradiation Options for Previously Irradiated Prostate cancer (RO-PIP): Feasibility study investigating toxicity outcomes following reirradiation with stereotactic body radiotherapy (SBRT) versus high-dose-rate brachytherapy (HDR-BT)

INTRODUCTION

Radiotherapy is the most common curative treatment for non-metastatic prostate cancer; however, up to 13% of patients will develop local recurrence within 10 years. Patients can undergo further and potentially curative treatment including salvage surgery, brachytherapy (BT), external beam radiotherapy, high-intensity focused ultrasound and cryotherapy. Systematic review shows that high-dose-rate (HDR) BT and stereotactic body radiotherapy (SBRT) have the best outcomes in terms of biochemical control and lowest side effects. The reirradiation options for previously irradiated prostate cancer (RO-PIP) trial aims to determine the feasibility of recruitment to a trial randomising patients to salvage HDR-BT or SBRT and provide prospective data on patient recorded toxicity outcomes that will inform a future phase III trial.

METHODS AND ANALYSIS

The primary endpoint of the RO-PIP feasibility study is to evaluate the patient recruitment potential over 2 years to a trial randomising to either SBRT or HDR-BT for patients who develop local recurrence of prostate cancer following previous radiation therapy. The aim is to recruit 60 patients across 3 sites over 2 years and randomise 1:1 to SBRT or HDR-BT. Secondary objectives include recording clinician and patient-reported outcome measures to evaluate treatment-related toxicity. In addition, the study aims to identify potential imaging, genomic and proteomic biomarkers that are predictive of toxicity and outcome based on hypoxia status, a prognostic marker of prostate cancer.

ETHICS AND DISSEMINATION

This study has been approved by the Yorkshire and The Humber-Bradford Leeds Research Ethics Committee (Reference: 21/YH/0305, IRAS: 297060, January 2022). The results will be presented in national and international conferences, published in peer-reviewed journals and will be communicated to relevant stakeholders. A plain English report will be shared with the study participants, patients' organisations and media.

TRIAL REGISTRATION NUMBER

ISRCTN 12238218 (Amy Ackroyd NIHR CPMS Team).

A Prospective Study of MR-Guided Focal Salvage High Dose-Rate Brachytherapy for Radiorecurrent Prostate Cancer: Updated Results of 30 Patients

PURPOSE

Limited prospective data on focal salvage high dose-rate (HDR) prostate brachytherapy are available. We sought to explore the toxicities, health related quality of life (HRQOL) and efficacy of focal salvage HDR brachytherapy in a prospective clinical trial. This report represents updated results of previously published data.

MATERIALS AND METHODS

Patients with locally recurrent prostate cancer after previous external beam radiotherapy and/or brachytherapy were enrolled. Patients received MRI-guided, ultrasound-based focal HDR brachytherapy delivered over two fractions of 13.5 Gy delivered 1-2 weeks apart. Androgen deprivation therapy (ADT) was not used.

RESULTS

Thirty patients were treated between 2012-2019. At a median follow-up of 39 months, the three-year biochemical failure-free rate was 61.8% (95% CI 44.0-86.6%), and three-year ADT/salvage therapy-free rate was 86.0% (95% CI 74.1-99.8%). Seventeen patients experienced subsequent biochemical failure, 9 have received ADT and/or further local salvage, and no patients have died from prostate cancer. Of the 28 patients who had a post-treatment MRI, 26 had a local treatment response. No acute grade ≥ 3 GU/GI toxicity was observed. One temporary late grade 3 GU toxicity event occurred, and no late grade ≥ 3 GI toxicity was seen. No significant decline in urinary or bowel HRQOL was observed.

CONCLUSIONS

Focal salvage HDR brachytherapy has a favourable side effect profile, no significant decline in HRQOL and 3-year biochemical control rates in line with other salvage options. While early MRI response at the treated site is common, this does not preclude subsequent biochemical failure.

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.

Magnetic Resonance-Guided Reirradiation for Local Recurrence within the Prostate or in the Prostate Bed: One-Year Clinical Results of a Prospective Registry Study

Around 33% of patients treated by EBRT or brachytherapy will present a biochemical recurrence. SBRT is a new option for the treatment of patients with local-only recurrence. MRgRT seems to be interesting for the treatment of these recurrences. This article presents the one-year late tolerance and biochemical recurrence-free survival results of a prospective registry study. Patients with intraprostatic (or in the prostate bed) recurrence were treated with 5 to 9 fractions (median dose of 30 Gy in 5 fractions) with the MRIdian® system. PSA level and toxicities were evaluated before treatment and at three, six and 12 months after treatment. Thirty-seven patients with a median age of 74.5 years old were treated between 21 October 2019 and 7 December 2020. Acute tolerance was excellent with no grade >2 toxicities. Twelve months after treatment, we observed an increase of grade 1−2 dysuria (46% vs. 13% before treatment) and grade 1 polyuria (73% vs. 7%). The six, nine and 12-months biochemical-recurrence free survival were 97.3%, 86.5% and 65.0%. Fifteen patients (40%) presented a biochemical recurrence. Nine of these 15 patients (60%) had a persistent disease within the treated volume. In conclusion, MRgRT is safe and has promising survival results.

Clinical and technical challenges of cancer reirradiation: Words of wisdom

Since the development of new radiotherapy techniques that have improved healthy tissue sparing, reirradiation (reRT) has become possible. The selection of patients eligible for reRT is complex given that it can induce severe or even fatal side effects. The first step should therefore be to assess, in the context of multidisciplinary staff meeting, the patient's physical status, the presence of sequelae resulting from the first irradiation and the best treatment option available. ReRT can be performed either curatively or palliatively to treat a cancer-related symptom that is detrimental to the patient's quality of life. The selected techniques for reRT should provide the best protection of healthy tissue. The construction of target volumes and the evaluation of constraints regarding the doses that can be used in this context have not yet been fully codified. These points raised in the literature suggest that randomized studies should be undertaken to answer pending questions.

Efficacy and toxicity following salvage high-dose-rate brachytherapy for locally recurrent prostate cancer after radiotherapy

INTRODUCTION

The management of local relapse after prostate cancer radiotherapy is frequently based on androgen deprivation therapy. The aim of the study was to report Gustave Roussy's experience with salvage prostate brachytherapy.

PATIENTS AND METHODS

All cases of localized prostate cancer presenting in an irradiated area who received salvage high dose rate (HDR) brachytherapy from 2013 to 2020 were retrospectively reviewed.

RESULTS

A total of 64 patients were included. Median follow up was 30.5 months. Median initial EBRT dose was 70 Gy [Q1-Q3: 70 - 74]. Median PSA at brachytherapy was 6.8 ng/mL [Q1-Q3: 4.4 - 8.7] with a median interval between first and salvage irradiation of 10 years [Q1-Q3: 6.9 - 12.6]. The modality of the first irradiation was an exclusive EBRT in 73% of the cases, mostly with a 3D technique (82%). Dose prescription was two fractions of 12 Gy or 13 Gy associated with androgen deprivation therapy for 63% of the patients. About 23% of the patients were castrate-resistant. Disease free survival at 2 years was 58% in the whole population and 66% in hormone sensitive patients. The only factors associated with disease free survival on multivariate analysis was a high-risk disease at initial diagnosis (HR = 3.59, IC95 [1.75; 7.39], p = 0.0005). Grade 3 urinary and rectal toxicities occurred in 1.5% and 1.5% of the patients, respectively.

CONCLUSION

HDR salvage brachytherapy seems to be a safe option for patients presenting with an isolated local relapse of prostate cancer.

Defining radio-recurrent intra-prostatic target volumes using PSMA-targeted PET/CT and multi-parametric MRI

PURPOSE

Our purpose was to evaluate intra-prostatic cancer volumes for salvage radiotherapy in men with recurrent prostate cancer confined to the prostate post-primary radiotherapy using mpMRI and 18F-DCFPyL PET/CT (PET).

METHODS

Men with biochemical failure post-primary radiotherapy were enrolled in a multi-centre trial investigating mpMRI and PET. All men with isolated intra-prostatic recurrence are included in this secondary analysis. The intra-prostatic gross tumour volume (GTV) was manually delineated on mpMRI and was also delineated on PET using three methods: 1. manually, 2. using a 30% threshold of maximum intra-prostatic standard uptake value (SUVmax), and 3. using a 67% threshold of this SUVmax. Clinical target volumes (CTV) including expansions on each GTV were generated. Conformity indices were performed between the mpMRI CTV and each PET CTV. Correlation with biopsy and clinical outcomes were performed.

RESULTS

Of the 36 men included, 30 (83%) had disease in two quadrants or less using the combination of mpMRI and PET. Mean target volume (union of CTV on mpMRI and CTV manually delineated on PET) was 12.2 cc (49% of prostate gland volume). 12/36 (33%) men had a biopsy. Per-patient sensitivity was 91% for mpMRI and 82% for PET.

CONCLUSIONS

mpMRI and PET provide complementary information for delineation of intra-prostatic recurrent disease. Union of CTV on mpMRI and PET is often less than 50% of the prostate, suggesting this imaging could help define a target for focal salvage therapy.

Design of the novel ThermoBrachy applicators enabling simultaneous interstitial hyperthermia and high dose rate brachytherapy

OBJECTIVE

In High Dose Rate Brachytherapy for prostate cancer there is a need for a new way of increasing cancer cell kill in combination with a stable dose to the organs at risk. In this study, we propose a novel ThermoBrachy applicator that offers the unique ability to apply interstitial hyperthermia while simultaneously serving as an afterloading catheter for high dose rate brachytherapy for prostate cancer. This approach achieves a higher thermal enhancement ratio than in sequential application of radiation and hyperthermia and has the potential to decrease the overall treatment time.

METHODS

The new applicator uses the principle of capacitively coupled electrodes. We performed a proof of concept experiment to demostrate the feasibility of the proposed applicator. Moreover, we used electromagnetic and thermal simulations to evaluate the power needs and temperature homogeneity in different tissues. Furthermore we investigated whether dynamic phase and amplitude adaptation can be used to improve longitudinal temperature control.

RESULTS

Simulations demonstrate that the electrodes achieve good temperature homogeneity in a homogenous phantom when following current applicator spacing guidelines. Furthermore, we demonstrate that by dynamic phase and amplitude adaptation provides a great advancement for further adaptability of the heating pattern.

CONCLUSIONS

This newly designed ThermoBrachy applicator has the potential to revise the interest in interstitial thermobrachytherapy, since the simultaneous application of radiation and hyperthermia enables maximum thermal enhancement and at maximum efficiency for patient and organization.

Magnetic Resonance-Guided Reirradiation for Local Recurrence Within the Prostate or in the Prostate Bed: Preliminary Results of a Prospective Registry Study

Purpose

This prospective registry study evaluated the feasibility of stereotactic magnetic resonance imaging (MRI)–guided radiation therapy for the local treatment of isolated prostate cancer recurrence within the gland or prostate bed after primary radiation therapy.

Methods and Materials

Patients with isolated recurrence without any regional or distant extension after treatment by external radiation therapy of the prostate gland/bed or by prostate brachytherapy were included. A 173-second Fast Imaging with Steady state Precession (TrueFISP) sequence was used for MRI simulation, and the gross tumor volume was delineated using multimodal images. The initial treatment plan varied from 27.5 Gy in 5 fractions to 38.7 Gy in 9 fractions and was adapted at each session, if necessary. The primary endpoint was acute toxicities (according to the Common Terminology Criteria for Adverse Events v5.0 criteria). Secondary endpoints were the effects of the adaptive treatment on target volume coverage, late toxicities, and oncologic events.

Results

Twenty patients were included. After a minimum follow-up of 6 months, grade 2 dysuria (from grade 1 at baseline; n = 1), grade 2 polyuria (n = 1), grade 1 urinary incontinence (n = 1), grade 1 urinary pain (n = 2), and grade 1 diarrhea (n = 1) were reported.

All initial treatment plans met the tumor coverage objectives, with a mean 95% planning target volume value of 95.7%. No plan exceeded the bladder and rectum dose constraints, but 8 exceeded the urethra dose constraints because of urethra proximity to the planning target volume. The initial plan was adapted in 7 patients (35%). The tumor coverage improved by 3.7% compared with the predicted plan (P = .0001) without increase in the dose to organs at risk. The biochemical control rate for the whole cohort was 75% (15/20 patients) including the 4 patients who received androgen-deprivation therapy.

Conclusions

MRI-guided reirradiation for isolated recurrence within the prostate or in the prostate bed appears to be safe with excellent dosimetric results.

ACR-ABS-ASTRO practice parameter for the performance of radionuclide-based high-dose-rate brachytherapy

PURPOSE

This practice parameter aims to detail the processes, qualifications of personnel, patient selection, equipment, patient and personnel safety, documentation, and quality control and improvement necessary for an HDR brachytherapy program.

METHODS AND MATERIALS

This practice parameter was revised collaboratively by the American College of Radiology (ACR), the American Brachytherapy Society (ABS), and the American Society for Radiation Oncology (ASTRO).

RESULTS

Brachytherapy is a radiotherapeutic modality in which radionuclide or electronic sources are used to deliver a radiation dose at a distance of up to a few centimeters by surface, intracavitary, intraluminal, or interstitial application. Brachytherapy alone or combined with external beam radiotherapy plays an important role in the management and treatment of patients with cancer. High-dose-rate (HDR) brachytherapy uses radionuclides, such as iridium-192, at dose rates of ≥12 Gy/hr to a designated target point or volume, and it is an important treatment for a variety of malignant and benign conditions. Its use allows for application of high doses of radiation to defined target volumes with relative sparing of adjacent critical structures.

CONCLUSIONS

HDR brachytherapy requires detailed attention to personnel, equipment, patient and personnel safety, and continuing staff education. Coordination between the radiation oncologist and treatment planning staff and effective quality assurance procedures are important components of successful HDR brachytherapy programs.

Salvage Reirradiation Options for Locally Recurrent Prostate Cancer: A Systematic Review

BACKGROUND

Reirradiation using brachytherapy (BT) and external beam radiation therapy (EBRT) are salvage strategies with locally radiorecurrent prostate cancer. This systematic review describes the oncologic and toxicity outcomes for salvage BT and EBRT [including Stereotactic Body Radiation Therapy (SBRT)].

METHODS

An International Prospective Register of Systematic Reviews (PROSPERO) registered (#211875) study was conducted using Preferred Reporting Items for Systematic reviews and Meta-analyses (PRISMA) guidelines. EMBASE and MEDLINE databases were searched from inception to December 2020. For BT, both low dose rate (LDR) and high dose rate (HDR) BT techniques were included. Two authors independently assessed study quality using the 18-item Modified Delphi technique.

RESULTS

A total of 39 eligible studies comprising 1967 patients were included (28 BT and 11 SBRT). In 35 studies (90%), the design was single centre and/or retrospective and no randomised prospective studies were found. Twelve BT studies used LDR only, 11 HDR only, 4 LDR or HDR and 1 pulsed-dose rate only. All EBRT studies used SBRT exclusively, four with Cyberknife alone and 7 using both Cyberknife and conventional linear accelerator treatments. Median (range) modified Delphi quality score was 15 (6-18). Median (range) follow-up was 47.5 months (13-108) (BT) and 25.4 months (21-44) (SBRT). For the LDR-BT studies, the median (range) 2-year and 5-year bRFS rates were 71% (48-89.5) and 52.5% (20-79). For the HDR-BT studies, the median (range) 2-year and 5-year bRFS rates were 74% (63-89) and 51% (45-65). For the SBRT studies, the median (range) 2-year bRFS for the SBRT group was 54.9% (40-80). Mean (range) acute and late grade≥3 GU toxicity rates for LDR-BT/HDR-BT/SBRT were 7.4%(0-14)/2%(0-14)/2.7%(0-8.7) and 13.6%(0-30)/7.9%(0-21.3%)/2.7%(0-8%). Mean (range) acute and late grade≥3 GI toxicity rates for LDR-BT/HDR-BT/SBRT were 6.5%(0-19)/0%/0.5%(0-4%) and 6.4%(0-20)/0.1%(0-0.9)/0.2%(0-1.5). One third of studies included Patient Reported Outcome Measures (PROMs).

CONCLUSIONS

Salvage reirradiation of radiorecurrent prostate cancer using HDR-BT or SBRT provides similar biochemical control and acceptable late toxicity. Salvage LDR-BT is associated with higher late GU/GI toxicity. Challenges exist in comparing BT and SBRT from inconsistencies in reporting with missing data, and prospective randomised trials are needed.

Commissioning of an intra-operative US guided prostate HDR system integrating an EM tracking technology

PURPOSE

Ultrasound-based planning for high-dose-rate prostate brachytherapy is commonly used in the clinic, mainly because it offers fast real-time image-guided capability at a relatively low cost. The main difficulty with US planning is the catheter reconstruction due to artefacts (from multiple catheters) and echogenicity. Electromagnetic tracking (EMT) system offers a fast and accurate solution for automatic reconstruction of catheters using the EMT technology. In this study, the commissioning and performance evaluation of the new real-time prostate high-dose-rate brachytherapy investigational system from Philips Disease Management Solutions integrating EMT was performed before its clinical integration.

METHOD AND MATERIALS

The Philips' clinical investigational system includes a treatment planning software (TPS) that was commissioned based on AAPM TG53 and TG56 recommendations for the use of TPS in brachytherapy. First, the CIRS - model 045A - QA phantom was used to evaluate the ultrasound (US) image quality and 3D image handling. Distances, volumes, and dimensions of the structures inside the phantom were measured and compared to the actual values. The calibration reproducibility and accuracy of the electromagnetic (EM) sensor used to track the US probe (rotation and translation) were performed using a specifically designed QA tool mounted on the probe and immersed in a salted water tank. This was performed for 3 different B&K 8848 US probes to evaluate the sensitivity of EM calibration to the probe geometric properties (manufacturing process). The new TPS performance was compared to that in OncentraBrachy (OcB) V4.5.5 (Elekta) using 30 clinical cases as part of a retrospective study. Following the system commissioning, clinical workflows were explored; tests were performed with the brachytherapy team on phantoms and finally implemented in the clinic.

RESULTS

US image quality evaluation showed a mean difference with actual dimensions (lengths, widths and distances) of 0.4 mm (±0.3 mm) and mean difference in volume sizes of 0.2 cc (±0.2 cc). Then, the calibration of the US-to-EM coordinate system was performed for 3 different probes. For each probe, 3 measurements were acquired for every position of the calibration tool and measurements were repeated 3 times for a total of 27 measurements per probe per plane. The error was slightly higher in transverse mode compared to sagittal mode with mean values of 0.6 ± 0.2 mm and 0.3 ± 0.1 mm respectively. 30 clinical cases were used to compare the new TPS performance to OcB (IPSA). Optimized plans obtained with both systems were all clinically acceptable, but the plans from the Philips system have slightly higher V150% values, V200% values and dose to organs at risk. In the case of organs at risk, plans could have been manually modified to reduce the dose. Philips' system had a larger number of active dwell positions and longer treatment times.

CONCLUSIONS

The first clinical version of Philips' system was proven to be stable, accurate and precise. The fully integrated EM tracking technology opens the way for automated catheter reconstruction and on-the-fly dynamical replanning.

Nonmetastatic castration-resistant prostate cancer treated with salvage focal brachytherapy after external beam radiotherapy

INTRODUCTION

The efficacy of salvage local therapy after external beam radiotherapy has recently gained attention. However, a challenge with these therapies is the risk of significant genitourinary and gastrointestinal toxicity. Focal brachytherapy may be a treatment option because of its potential to reduce side effects.

CASE PRESENTATION

A patient with castration-resistant prostate cancer was found to be free of metastases on whole-body magnetic resonance imaging following external beam radiotherapy, and prostate biopsy revealed a localized recurrence in the ventral prostate. The patient underwent salvage focal brachytherapy and had a prostate-specific antigen progression-free survival of 23 months. No adverse effects were observed following salvage brachytherapy.

CONCLUSION

Our case suggests that salvage focal brachytherapy may be an effective local treatment option for nonmetastatic castration-resistant prostate cancer that has relapsed after external beam radiotherapy, wherein the lesion is confined to a small area within the prostate.

Development and internal validation of multivariable prediction models for biochemical failure after MRI-guided focal salvage high-dose-rate brachytherapy for radiorecurrent prostate cancer

Background and purpose

Magnetic resonance-guided focal salvage high-dose-rate brachytherapy (FS-HDR-BT) for radiorecurrent prostate cancer (PCa) shows low toxicity rates. However, biochemical failure (BF) after treatment occurs frequently. We developed two prediction models for BF (Phoenix definition) with the aim of enhancing patient counselling before FS-HDR-BT and during follow-up.

Materials and methods

A prospective cohort of 150 radiorecurrent PCa patients treated with FS-HDR-BT between 2013 and 2020 was used for model development and internal validation. Multivariable Cox Proportional Hazards regression was applied. For model 1, only pre-salvage variables were included as candidate predictors. For model 2, additional (post-)salvage characteristics were tested. After calibration, nomograms and webtools were constructed. Finally, three risk groups were identified.

Results

Sixty-one patients (41%) experienced BF. At baseline (model 1), age, gross tumour volume, pre-salvage PSA, and pre-salvage PSA doubling time (PSADT) were predictive of BF. During follow-up (model 2), age, pre-salvage PSA and PSADT, seminal vesicle involvement, post-salvage time to PSA nadir, and percentage PSA reduction were predictive of BF. The adjusted C-statistics were 0.73 (95% CI: 0.66-0.81) and 0.84 (95% CI: 0.78-0.90), respectively, with acceptable calibration. Estimated 2-year biochemical disease-free survival for the low-, intermediate-, and high-risk groups were 84%, 70%, and 31% (model 1), and 100%, 71%, and 5% (model 2).

Conclusion

Two models are provided for prediction of BF in patients with radiorecurrent PCa treated with FS-HDR-BT. Based on pre- and post-salvage characteristics, we are able to identify patients with a high risk of BF. These findings can aid patient counselling for FS-HDR-BT.

High-dose-rate brachytherapy for prostate cancer: Rationale, current applications, and clinical outcome

Background

High‐dose‐rate brachytherapy (HDR BRT) has been enjoying rapid acceptance as a treatment modality offered to selected prostate cancer patients devoid of risk group, employed either in monotherapy setting or combined with external beam radiation therapy (EBRT) and is currently one of the most active clinical research areas.

Recent findings

This review encompasses all the current evidence to support the use of HDR BRT in various clinical scenario and shines light to the HDR BRT rationale, as an ultimately conformal dose delivery method enabling safe dose escalation to the prostate.

Conclusion

Valid long‐term data, both in regard to the oncologic outcomes and toxicity profile, support the current clinical indication spectrum of HDR BRT. At the same time, this serves as solid, rigid ground for emerging therapeutic applications, allowing the technique to remain in the spotlight alongside stereotactic radiosurgery.

Artificial intelligence and imaging biomarkers for prostate radiation therapy during and after treatment

Magnetic resonance imaging (MRI) is increasingly used in the management of prostate cancer (PCa). Quantitative MRI (qMRI) parameters, derived from multi-parametric MRI, provide indirect measures of tumour characteristics such as cellularity, angiogenesis and hypoxia. Using Artificial Intelligence (AI), relevant information and patterns can be efficiently identified in these complex data to develop quantitative imaging biomarkers (QIBs) of tumour function and biology. Such QIBs have already demonstrated potential in the diagnosis and staging of PCa. In this review, we explore the role of these QIBs in monitoring treatment response during and after PCa radiotherapy (RT). Recurrence of PCa after RT is not uncommon, and early detection prior to development of metastases provides an opportunity for salvage treatments with curative intent. However, the current method of monitoring treatment response using prostate-specific antigen levels lacks specificity. QIBs, derived from qMRI and developed using AI techniques, can be used to monitor biological changes post-RT providing the potential for accurate and early diagnosis of recurrent disease.

Salvage High-Dose-Rate Brachytherapy for Recurrent Prostate Cancer After Definitive Radiation

PURPOSE

Salvage high-dose-rate brachytherapy (sHDRBT) for locally recurrent prostate cancer after definitive radiation is associated with biochemical control in approximately half of patients at 3 to 5 years. Given potential toxicity, patient selection is critical. We present our institutional experience with sHDRBT and validate a recursive partitioning machines model for biochemical control.

MATERIALS AND METHODS

We performed a retrospective analysis of 129 patients who underwent whole-gland sHDRBT between 1998 and 2016. We evaluated clinical factors associated with biochemical control as well as toxicity.

RESULTS

At diagnosis the median prostate-specific antigen (PSA) was 7.77 ng/mL. A majority of patients had T1-2 (73%) and Gleason 6-7 (82%) disease; 71% received external beam radiation therapy (RT) alone, and 22% received permanent prostate implants. The median disease-free interval (DFI) was 56 months, and median presalvage PSA was 4.95 ng/mL. At sHDRBT, 46% had T3 disease and 51% had Gleason 8 to 10 disease. At a median of 68 months after sHDRBT, 3- and 5-year disease-free survival were 85% (95% CI, 79-91) and 71% (95% CI, 62-79), respectively. Median PSA nadir was 0.18 ng/mL, achieved a median of 10 months after sHDRBT. Patients with ≥35%+ cores and a DFI <4.1 years had worse biochemical control (19% vs 50%, P = .02). Local failure (with or without regional/distant failure) was seen in 11% of patients (14/129), and 14 patients (11%) developed acute urinary obstruction requiring Foley placement and 19 patients (15%) developed strictures requiring dilation.

CONCLUSIONS

sHDRBT is a reasonable option for patients with locally recurrent prostate cancer after definitive RT. Those with <35%+ cores or an initial DFI of ≥4.1 years may be more likely to achieve long-term disease control after sHDRBT.

Focal salvage treatment for radiorecurrent prostate cancer: A magnetic resonance-guided stereotactic body radiotherapy versus high-dose-rate brachytherapy planning study

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SBRT may provide a non-invasive treatment option for recurrent prostate cancer.

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MR-Linac single fraction 19 Gy treatment of recurrent prostate cancer is feasible.

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MR-Linac dose distributions for the target were comparable to HDR-brachytherapy.

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Real-time intrafraction adaptation techniques are needed for clinical introduction.

Background and Purpose

Magnetic resonance imaging (MRI)-guided focal salvage high-dose-rate brachytherapy (FS-HDR-BT) is one of the treatment options for radiorecurrent localized prostate cancer. However, due to the invasive nature of the treatment, not all patients are eligible. Magnetic resonance linear accelerator (MR-Linac) systems open up new treatment possibilities and could potentially replace FS-HDR-BT treatment. We conducted a planning study to investigate the feasibility of delivering a single 19 Gy dose to the recurrent lesion using a 1.5 Tesla MR-Linac system.

Materials and Methods

Thirty patients who underwent FS-HDR-BT were included. The clinical target volume (CTV) encompassed the visible lesion plus a 5 mm margin. Treatment plans were created for a 1.5 Tesla MR-Linac system using a 1 mm planning target volume (PTV) margin. A dose of 19 Gy was prescribed to ≥ 95% of the PTV. In case this target could not be reached, i.e. when organs-at-risk (OAR) constraints were violated, a dose of ≥ 17 Gy to ≥ 90% of the PTV was accepted. MR-Linac plans were compared to clinical FS-HDR-BT plans.

Results

Target dose coverage was achieved in 14/30 (47%) FS-HDR-BT plans and 17/30 (57%) MR-Linac plans, with comparable median D95% and D90%. In FS-HDR-BT plans, a larger volume reached ≥ 150% of the prescribed dose. Urethra D10%, rectum D1cm³, and rectum D2cm³ were lower in the FS-HDR-BT plans, while bladder dose was comparable for both modalities.

Conclusion

Single fraction treatment of recurrent prostate cancer lesions may be feasible using stereotactic body radiotherapy (SBRT) on a MR-Linac system.

Prostate high dose-rate brachytherapy as monotherapy for prostate cancer: Late toxicity and patient reported outcomes from a randomized phase II clinical trial

BACKGROUND AND PURPOSE

Long-term toxicity of high dose-rate brachytherapy as monotherapy for prostate cancer is not well defined. We report late toxicity and health related quality of life (HRQOL) changes from a randomized phase II clinical trial of two different fractionation schemes.

MATERIALS AND METHODS

Eligible patients had NCCN low or intermediate risk prostate cancer. 170 patients were randomized to receive either a single 19 Gy or two-fractions of 13.5 Gy one week apart. Toxicity was measured using Common Terminology for Adverse Events (CTCAE) v4.0, and HRQOL was measured using the Expanded Prostate Index Composite (EPIC).

RESULTS

Median follow-up was 63 months. The 5-year cumulative incidence of Grade 2 or higher genitourinary (GU) and gastrointestinal (GI) toxicity was 62% and 12% in the single-fraction arm, and 47% and 9% in the two-fraction arm, respectively. Grade 3 GU toxicity was only seen in the single fraction arm with a cumulative incidence of 2%. The 5-year prevalence of Grade 2 GU toxicity was 29% and 21%, in the single- and two-fraction arms, respectively, with Grade 2 GI toxicity of 1% and 2%. Beyond the first year, no significant differences in mean urinary HRQOL were seen compared to baseline in the two-fraction arm, in contrast to the single-fraction arm where a decline in urinary HRQOL was seen at 4 and 5 years. Sexual HRQOL was significantly reduced in both treatment arms at all timepoints, with no changes in the bowel domain.

CONCLUSIONS

HDR monotherapy is well tolerated with minimal impact on HRQOL.

Determining the safety of ultrafocal salvage high-dose-rate brachytherapy for radiorecurrent prostate cancer: A toxicity assessment of 150 patients

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Severe toxicity is as low as 3% (GU), 0% (GI) and 15% (ED).

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Lower impact is predicted for patients with favorable function at baseline.

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Lower dose to the urethra (D10% <17 Gy) may prevent urinary symptoms.

Background and purpose

Local re-treatment of radiorecurrent prostate cancer is potentially curative. However, the increased risk of severe toxicity may outweigh the opportunity of cancer control. This study aims to evaluate treatment-related toxicity from ultrafocal salvage high-dose-rate brachytherapy (HDR-BT) and to investigate potential risk factors.

Materials and methods

Toxicity data from 150 treated patients (July 2013–November 2019) was collected from a prospective registry. The treatment aim was to deliver a single dose of 19 Gy to the recurrent lesion as identified on multiparametric MRI and PET-CT. Treating physicians graded genitourinary (GU) and gastro-intestinal (GI) toxicity and erectile dysfunction (ED) using the Common Terminology Criteria for Adverse Events (CTCAE) 4.0, at baseline and during follow-up. Domains with substantial (≥10%) new-onset grade ≥ 2 toxicity were further evaluated using mixed effects logistic regression to find potential risk factors.

Results

Median follow-up time was 20 months (IQR 12–31). Over time, new-onset grade 2 and 3 toxicity was recorded in 41% and 3% (GU), 5% and 0% (GI) and 22% and 15% (ED). While GI toxicity remained stably low, grade ≥ 2 GU toxicity and ED were seen twice as frequent in the late phase (>3 months after treatment). Significant risk factors for grade ≥ 2 toxicity were baseline GU toxicity (grade ≥ 2), baseline ED (grade ≥ 2), IPSS (cut-off ≥ 14) and urethral dose (D10%, cut-off ≥ 17 Gy).

Conclusion

Ultrafocal salvage HDR-BT is a safe re-treatment option, especially in patients with a favorable symptom profile at baseline. Adherence to urethral dose constraints is important to avoid GU toxicity.

Health-related quality of life after ultrafocal salvage high-dose-rate brachytherapy for radiorecurrent prostate cancer: reporting the patient’s perspective

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We analyzed patient-reported quality of life in 100 patients who underwent ultrafocal salvage HDR-brachytherapy.

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Patient-reported bowel symptoms were neglible.

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Urinary complaints increased and sexual functioning declined over time.

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Lower impact is predicted for patients with favorable function at baseline and lower dose to the urethra.

Purpose

For patients with a localized prostate cancer recurrence after radiotherapy, focal salvage treatment offers a less toxic alternative to whole-gland treatments, with the potential of preserving health-related quality of life (HR-QoL). With a focus on the patient’s perspective of treatment, this study aims to describe HR-QoL after ultrafocal salvage high-dose-rate brachytherapy (HDR-BT), and to explore predictive factors affecting HR-QoL.

Material and methods

We included 100 patients treated with ultrafocal salvage HDR-BT. Prostate cancer-related HR-QoL was assessed by the EORTC QLQ-PR25 questionnaire. Domains were urinary symptoms, bowel symptoms and sexual activity/functioning. For each domain, a mixed effects model was made to estimate HR-QoL trends over time. For domains showing clinically relevant change (≥10 points difference), the mixed effects model was used to explore potential predictors (age, baseline HR-QoL score, T-stage, tumor location, CTV size, dose to organs at risk and history of ADT).

Results

Median follow-up was 20 months (IQR 13–30). Mean questionnaire response rate was 86% (range 72–100%). Median baseline scores were 12 (urinary), 0 (bowel) and 67/50 (sexual activity/functioning). Urinary symptoms and sexual functioning showed clinically relevant deterioration over time (maximum difference of 11 and 12 points, respectively). Worse baseline score and higher administered dose to the urethra (≥16 Gy) were predictive of increased urinary symptoms (p < 0.01 and p = 0.03). Better baseline score was predictive of better sexual functioning (p < 0.01).

Conclusion

Ultrafocal salvage HDR-BT has negligible impact on bowel symptoms but does affect urinary symptoms and sexual functioning. Lower impact is predicted for patients with favorable urinary and sexual function at baseline. Urethral dose constraints should be closely monitored.

Salvage low-dose-rate brachytherapy for local recurrences after prostatectomy and adjuvant or salvage external beam irradiation: Feasibility study on five patients and literature review

PURPOSE

To assess the feasibility and tumor outcome of re-irradiation with low-dose-rate brachytherapy for macroscopic local recurrences after radical prostatectomy (RP) followed by adjuvant or salvage external beam radiation therapy (EBRT).

METHODS AND MATERIALS

Between 2011 and 2018, five men with histologically proven local failure within the prostate (4) or seminal vesicle bed (1) after RP and adjuvant or salvage EBRT (median dose: 67.5 Gy) underwent a salvage brachytherapy (S-BT). The median delay after EBRT was 86 months (range 75-234). Two patients were castration-resistant at the time of S-BT. The gross tumor volume was defined on a multiparametric MRI and transrectal US imaging. Echo-guided transperineal implants of Iodine-125 seeds were optimized with a per-operative dosimetry and delivered with the seed-selectron.

RESULTS

A high conformity was achieved with a high dose to the CTV (D_95% > 145 Gy in all but one) and very low dose to the rectum, urethra, and bladder. With a median followup of 21 months, all but one patient experienced nodes and/or bone metastases. Local control was achieved in 3/4 of evaluable patients (local failure distant to the treated volume in one). To date, no Grade 2 or more late toxicities were observed.

CONCLUSION

For selected patients, focal local recurrence brachytherapy after PR and EBRT appears technically feasible and safe, but the efficacy remains uncertain as the majority of patients quickly relapsed at other sites. Large prospective studies are still required to better select patients who will benefit from this strategy.

Salvage I-125 brachytherapy for locally-recurrent prostate cancer after radiotherapy

Purpose

Retrospective, single-institution analysis of clinical outcomes and treatment-related toxicity in patients treated with salvage I-125 low-dose rate (LDR) brachytherapy (BT) for locally-recurrent prostate cancer after radiotherapy.

Materials and methods

Between 2008 and 2018, 30 patients with biopsy-confirmed prostate cancer recurrence underwent salvage treatment with I-125 LDR-BT. Of these 30 patients, 14 were previously treated with primary external beam radiotherapy (EBRT; median dose, 73 Gy) and 16 with primary I-125 LDR-BT (145 Gy and 160 Gy in 14 and 2 cases, respectively). At seed implantation, the mean age was 75.8 years, with a median Gleason score of 7 and pre-salvage PSA of <10 ng/mL. Six patients received androgen deprivation therapy for six months after relapse diagnosis. The prescribed salvage I-125 BT dose to the gland was 120-130 Gy, with dose restrictions of Dmax <135% (urethra) and <100% (rectum). Toxicity was evaluated according to the CTCAE scale (v4.0).

Results

At a median follow-up of 45 months, the biochemical recurrence-free survival rates at 1, 3 and 5 years were 86.7%, 56.7% and 53.3%, respectively. Overall survival at 5 years was 87%. On the multivariate analysis, two variables were significant predictors of recurrence: PSA at relapse and nadir PSA post-salvage. Grade 3 genitourinary toxicity was observed in 5 patients (radiation-induced cystitis in 3 cases and urethral stenosis in 2) and G3 gastrointestinal toxicity in 3 patients (rectal bleeding).

Conclusion

Salvage therapy with I-125 brachytherapy is a safe and effective treatment option for locally-recurrent prostate cancer in previously-irradiated patients. High pre-salvage PSA and post-salvage nadir PSA values were significantly associated with a worse disease control after salvage I-125 LDR-BT. In well-selected patients, I-125 LDR-BT is comparable to other salvage therapies in terms of disease control and toxicity. However, more research is needed to determine the optimal management of locally-recurrent prostate cancer.

Interim Results of a Prospective Prostate-Specific Membrane Antigen-Directed Focal Stereotactic Reirradiation Trial for Locally Recurrent Prostate Cancer

PURPOSE

To report the feasibility, toxicity, and preliminary outcomes (metabolic and biochemical) of ⁶⁸Ga-prostate-specific membrane antigen (PSMA) positron emission tomography/computed tomography (PET/CT)-directed focal prostate reirradiation using linear accelerator (LINAC)-based stereotactic body radiation treatment (SBRT).

METHODS AND MATERIALS

From March 2016 to March 2019, 25 patients were enrolled in a prospective single institution trial (ACTRN12617000035325). Eligibility criteria included patients with biopsy proven isolated prostate recurrence after definitive irradiation, with concordant multiparametric MRI and ⁶⁸Ga-PSMA PET/CT findings, and a prostate-specific antigen of less than 15 ng/mL at the time of recurrence. The study included a sequential dose escalation component with the first 18 patients receiving 36 Gy in 6 fractions on alternate days with subsequent patients receiving 38 Gy in 6 fractions assuming acceptable toxicity.

RESULTS

Median age was 72 years (range, 62-83) with a median time between first radiation treatment and salvage SBRT of 8.3 years (range, 4.5- 13.6). Median prostate-specific antigen at reirradiation was 4.1 (range, 1.1-16.6). The median follow-up was 25 months (range, 13-46). Acute grade 1 and 2 genitourinary (GU) toxicity occurred in 6 (24%) and 1 (4%) men, respectively. Acute grade 1 gastrointestinal (GI) toxicity occurred in 8% with one acute grade 3 GI toxicity (4%) due to a rectal ulcer overlying the hydrogel. Late grade 1 and 2 GU toxicity occurred in 28% and 4%. Late grade 1 GI toxicity occurred in 8% with no grade 2 or greater toxicity. Twenty-four patients have undergone per-protocol 12-month ⁶⁸Ga-PSMA PET/CT, of which 23 (92%) demonstrated a complete metabolic response. Biochemical freedom from failure was 80% at 2 years with 3 out of 4 of the biochemical failures exhibiting recurrent local disease.

CONCLUSIONS

PSMA-directed salvage focal reirradiation to the prostate using linear accelerator-based SBRT is feasible and safe. Toxicity was low, with very favorable short term local and biochemical control in a carefully selected cohort of patients.

Modern development of high-dose-rate brachytherapy

Brachytherapy is an invasive therapy with placement of radiation source into or near the tumor. The difference between planning target volume and clinical target volume is minimal, and the dose out of the tumor reduces rapidly due to the inverse-square law. High-dose-rate brachytherapy enables three-dimensional image guidance, and currently, tumor dose as well as doses of the surrounding normal structures can be evaluated accurately. High-dose-rate brachytherapy is the utmost precision radiation therapy even surpassing carbon ion therapy. Biological disadvantages of high-dose rate have been overcome by the fractional irradiation. High-dose-rate brachytherapy is indispensable in the definitive radiation therapy of cervical cancer. Also in prostate cancer and breast cancer, high-dose-rate brachytherapy plays a significant role. Brachytherapy requires techniques and skills of radiation oncologists at the time of invasive placement of the radiation source into the tumor area. Education of young radiation oncologists is most urgent and important.

A systematic review of salvage focal therapies for localised non-metastatic radiorecurrent prostate cancer

Although radiotherapy to the prostate for cancer is effective, recurrence occurs in 10-15% within 5 years. Traditional salvage treatments for men with radiorecurrent prostate cancer comprise of watchful waiting (WW) with or without androgen deprivation therapy (ADT) or radical prostatectomy (RP). Neither strategy provides ideal therapeutic ratios. Salvage focal ablation is an emerging option. We performed a systematic review of the Medline and Embase databases for studies reporting outcomes of focal salvage brachytherapy (sBT), cryotherapy (sCT) or high-intensity focused ultrasound (sHIFU) for radiorecurrent prostate cancer (conception to April 2019). Results were screened for inclusion against predetermined eligibility criteria. Certain data were extracted, including rates of biochemical disease-free survival (BDFS), metastasis, conversion to second-line therapies and adverse events. Of a total 134 articles returned from the search, 15 studies (14 case series and 1 comparative study) reported outcomes after focal sBT [5], sCT [7] and sHIFU [3]. Cohort size varied depending on intervention, with eligible studies of sBT being small case series. Median follow-up ranged from 10 to 56 months. Although pre-salvage demographics were similar [median age range, 61-75 years; prostate-specific antigen (PSA) range, 2.8-5.5 ng/mL], there was heterogeneity in patient selection, individual treatment protocols and outcome reporting. At 3 years, BDFS ranged from 61% to 71.4% after sBT, 48.1-72.4% after sCT and 48% after sHIFU. Only studies of sCT reported 5-year BDFS, which ranged from 46.5% to 54.4%. Rates of metastasis were low after all salvage modalities, as were conversion to second-line therapies (although this was poorly reported). Grade 3 adverse events were rare. This systematic review indicates that salvage focal ablation of radiorecurrent prostate cancer provides acceptable oncological outcomes and is well tolerated. Unfortunately, there is heterogeneity in the study design of existing evidence. Level 1 research comparing salvage focal therapies to existing whole-gland strategies is needed to further establish the role of these promising treatments.

Efficacy and toxicity outcomes for patients treated with focal salvage high dose rate brachytherapy for locally recurrent prostate cancer

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Local recurrence of prostate cancer may be treated with salvage therapies.

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Focal salvage high dose rate brachytherapy provides good biochemical control.

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Severe genitourinary and gastrointestinal toxicities are low.

Introduction

Isolated local recurrence of prostate cancer following primary radiotherapy or brachytherapy may be treated with focal salvage high dose rate brachytherapy, although there remains an absence of high quality evidence to support this approach.

Methods

Men with prostate cancer treated consecutively between 2015 and 2018 using 19 Gy in a single fraction high dose rate brachytherapy (HDR) for locally recurrent prostate cancer were identified from an institutional database. Univariable analysis was performed to evaluate the relationship between patient, disease and treatment factors with biochemical progression free survival (bPFS).

Results

43 patients were eligible for evaluation. Median follow up duration was 26 months (range 1–60). Median bPFS was 35 months (95% confidence interval 25.6–44.4). Kaplan-Meier estimates for bPFS at 1, 2 and 3 years post salvage were 95.2%, 70.6% and 41.8% respectively. On univariable Cox regression analysis, only nadir PSA was significantly associated with bPFS although the majority of patients were also treated with androgen deprivation therapy. Only one late grade 3 genitourinary toxicity was observed.

Conclusion

Focal salvage HDR brachytherapy may provide good biochemical control with a low risk of severe toxicity. Further evaluation within clinical trials are needed to establish its role in the management of locally recurrent prostate cancer.

MRI-Guided Ultrafocal Salvage High-Dose-Rate Brachytherapy for Localized Radiorecurrent Prostate Cancer: Updated Results of 50 Patients

PURPOSE

Most patients with local prostate cancer recurrence after radiation therapy undergo palliative androgen deprivation therapy because whole-gland salvage treatments have a high risk of severe toxicity. Focal treatment reduces this risk while offering a second opportunity for cure. We report updated outcomes of ultrafocal salvage high-dose-rate brachytherapy (HDR-BT).

METHODS AND MATERIALS

Prospectively collected data from the first 50 treated patients were analyzed. Disease status was assessed by 3T multiparametric magnetic resonance imaging (MRI), 18F-Choline or 68Ga-prostate-specific membrane antigen positron emission tomography/computed tomography, and systematic or tumor-targeted biopsies. Ultrafocal salvage HDR-BT (1 × 19 Gy) was performed by implanting the clinical target volume (CTV: gross tumor volume + 5 mm margin) under fused transrectal ultrasound/MRI guidance. Follow-up included toxicity grading (using Common Terminology Criteria for Adverse Events 4.0), quality of life assessment, and prostate-specific antigen (PSA) testing.

RESULTS

Median follow-up was 31 months. Median CTV D95% was 18.8 Gy. We observed 2% grade 3 genitourinary toxicity, no grade 3 gastrointestinal toxicity, and 22% newly developed grade 3 erectile dysfunction. Five of 13 patients (38%) with self-reported pretreatment potency (International Index of Erectile Function >17) remained potent. Clinically relevant quality of life deterioration was reported for only 6 of 31 items and was not statistically significant. Biochemical failure (nadir + 2) occurred in 26 patients. Among intraprostatic recurrences, 73% were in field. After 2.5 years, biochemical disease-free survival was 51% (95% confidence interval, 37%-69%), metastases-free survival was 75% (64%-89%), androgen deprivation therapy-free survival was 90% (82%-99%), and overall survival was 98% (94%-100%). Presalvage PSA, CTV size, and stage ≥T3 were significantly associated with biochemical failure. Higher-risk patients (stage ≥T3, PSA ≥10, or PSA double time ≤9 months) had 25% biochemical disease-free survival at 2.5 years versus 71% for lower-risk patients.

CONCLUSIONS

At this early stage, MRI-guided ultrafocal HDR-BT seems to be a safe salvage treatment option, with acceptable biochemical control in a well-selected group of patients and potential for effectively postponing androgen deprivation therapy.

A Prospective Study of 18F-DCFPyL PSMA PET/CT Restaging in Recurrent Prostate Cancer following Primary External Beam Radiotherapy or Brachytherapy

PURPOSE

Radio-recurrent prostate cancer is typically detected by a rising prostate-specific antigen and may reflect local or distant disease. Positron emission tomography (PET) radiotracers targeting prostate-specific membrane antigen, such as 18F-DCFPyL have shown promise in restaging men with recurrent disease postprostatectomy but are less well characterized in the setting of radio-recurrent disease.

METHODS AND MATERIALS

A prospective, multi-institutional study was conducted to evaluate the effect of 18F-DCFPyL PET/computed tomography (CT) when added to diagnostic imaging (DI; CT abdomen and pelvis, bone scan, multiparametric magnetic resonance imaging pelvis) for men with radio-recurrent prostate cancer. All men were imaged with DI and subsequently underwent 18F-DCFPyL PET/CT with local and central reads. Tie break reads were performed as required. Management questionnaires were completed after DI and again after 18F-DCFPyL PET/CT. Discordance in patterns of disease detected with 18F-DCFPyL PET/CT versus DI and changes in management were characterized.

RESULTS

Seventy-nine men completed the study. Most men had T1 disease (62%) and Gleason score <7 (95%). Median prostate-specific antigen at diagnosis was 7.4 ng/mL and at relapse was 4.8 ng/mL. DI detected isolated intraprostatic recurrence in 38 out of 79 men (48%), regional nodal recurrence in 9 out of 79 (11%), distant disease in 12 out of 79 (15%), and no disease in 26 out of 79 (33%). 18F-DCFPyL PET/CT detected isolated intraprostatic recurrence in 38 out of 79 men (48%), regional nodal recurrence in 21 out of 79 (27%), distant disease in 24 out of 79 (30%), and no disease in 10 out of 79 (13%). DI identified 8 out of 79 (10%) patients to have oligometastatic disease, compared with 21 out of 79 (27%) with 18F-DCFPyL PET/CT. 18F-DCFPyL PET/CT changed proposed management in 34 out of 79 (43%) patients.

CONCLUSIONS

18F-DCFPyL PET/CT identified extraprostatic disease in twice as many men with radio-recurrent prostate cancer compared with DI and detected a site of recurrence in 87% of men compared with 67% with DI. Furthermore, 18F-DCFPyL PET/CT identified potentially actionable disease (prostate only recurrence or oligometastatic disease) in 75% of men and changed proposed management in 43% of men.

Case series illustrating the synergistic use of hydrogel spacer and MR-guidance to increase the radiotherapeutic index for localized prostate cancer

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Polyethylene glycol hydrogel spacer allows radiotherapy in challenging scenarios.

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Polyethylene glycol hydrogel material properties may limit broader applicability.

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MRI-guided brachytherapy unique scenario to use PEG without compromising prostate resolution.

Background

The risk of gastrointestinal (GI) toxicity may limit the use of curative-intent radical radiotherapy (RT) for prostate cancer (PCa) in circumstances where morbidity of treatment may exceed an acceptable threshold. Rectal spacers are used to expand the distance between the anterior rectal wall and the prostate, consequently sparing the rectum from the high-dose region.

Case presentations

We report three clinical scenarios of PCa patients treated at our institution, where risk of RT-associated rectal toxicity may be increased: inflammatory bowel disease (IBD), salvage brachytherapy (BT) after previous external beam RT (EBRT), and tailored dose-escalation with focal BT to the gross tumor volume followed by stereotactic body RT. Prior to RT, a polyethylene glycol (PEG) hydrogel spacer was successfully placed in all cases. Treatment comprised magnetic resonance (MR) guided high dose-rate BT ± EBRT. All patients completed treatment uneventfully, without any significant GI toxicity at last follow-up.

Conclusions

These cases illustrate the utility of PEG hydrogel spacer, where concerns of radiation induced toxicity may have previously limited the application of radiotherapy. The synergistic use of these novel devices together with MR-guided BT may expand the indications and therapeutic index of curative-intent RT-based treatments, while minimizing the risks of GI toxicity.

Results of 15 Gy HDR-BT boost plus EBRT in intermediate-risk prostate cancer: Analysis of over 500 patients

PURPOSE/OBJECTIVE

To report biochemical control associated with single fraction 15 Gy high-dose-rate brachytherapy (HDR-BT) boost followed by external beam radiation (EBRT) in patients with intermediate-risk prostate cancer.

MATERIALS AND METHODS

A retrospective chart review of all patients with intermediate-risk disease treated with a real-time ultrasound-based 15 Gy HDR-BT boost followed by EBRT between 2009 and 2016 at a single quaternary cancer center was performed. Freedom from biochemical failure (FFBF), cumulative incidence of androgen deprivation therapy use for biochemical or clinical failure post-treatment (CI of ADT) and metastasis-free survival (MFS) outcomes were measured.

RESULTS

518 patients met the inclusion criteria for this study. Median age at HDR-BT was 67 years (IQR 61-72). 506 (98%) had complete pathologic information available. Of these, 146 (28%) had favorable (FIR) and 360 (69%) had unfavorable (UIR) intermediate-risk disease. 83 (16%) received short course hormones with EBRT + HDR. Median overall follow-up was 5.2 years. FFBF was 91 (88-94)% at 5 years. Five-year FFBF was 94 (89-99)% and 89 (85-94)% in FIR and UIR patients, respectively (p = 0.045). CI of ADT was 4 (2-6)% at 5 years. Five-year CI of ADT was 1 (0-3)% and 5 (2-8)% in FIR and UIR patients, respectively (p = 0.085). MFS was 97 (95-98)% at 5 years. Five-year MFS was 100 (N/A-100)% and 95 (92-98)% in FIR and UIR patients, respectively (p = 0.020).

CONCLUSION

In this large cohort of intermediate-risk prostate cancer patients, 15 Gy HDR-BT boost plus EBRT results in durable biochemical control and low rates of ADT use for biochemical failure.

Salvage reirradiation for local prostate cancer recurrence after radiation therapy. For who? When? How?

PURPOSE

Literature review reporting results of salvage brachytherapy and stereotactic body radiotherapy for prostate recurrence only after radiotherapy for prostate cancer.

MATERIALS AND METHODS

A total of 38 studies (including at least 15 patients per study) were analysed: 19 using low-dose-rate brachytherapy, nine high-dose-rate brachytherapy and ten stereotactic body radiotherapy. Only five studies were prospective. The median numbers of patients were 30 for low-dose-rate brachytherapy, 34 for high-dose-rate brachytherapy, and 30 for stereotactic body radiotherapy. The median follow-up were 47months for low-dose-rate brachytherapy, 36months for high-dose-rate brachytherapy and 21months for stereotactic body radiotherapy.

RESULTS

Late genitourinary toxicity rates ranged, for grade 2: from 4 to 42% for low-dose-rate brachytherapy, from 7 to 54% for high-dose-rate brachytherapy and from 3 to 20% for stereotactic body radiotherapy, and for grade 3 or above: from 0 to 24% for low-dose-rate brachytherapy, from 0 to 13% for high-dose-rate brachytherapy and from 0 to 3% for grade 3 or above (except 12% in one study) for stereotactic body radiotherapy. Late gastrointestinal toxicity rates ranged, for grade 2: from 0 to 6% for low-dose-rate brachytherapy, from 0 to 14% for high-dose-rate brachytherapy and from 0 to 11% for stereotactic body radiotherapy, and for grade 3 or above: from 0 to 6% for low-dose-rate brachytherapy, and from 0 to 1% for high-dose-rate brachytherapy and stereotactic body radiotherapy. The 5-year biochemical disease-free survival rates ranged from 20 to 77% for low-dose-rate brachytherapy and from 51 to 68% for high-dose-rate brachytherapy. The 2- and 3-year disease-free survival rates ranged from 40 to 82% for stereotactic body radiotherapy. Prognostic factors of biochemical recurrence have been identified.

CONCLUSION

Despite a lack of prospective data, salvage reirradiation for prostate cancer recurrence can be proposed to highly selected patients and tumours. Prospective comparative studies are needed.

Changes in ADC and T2-weighted MRI-derived radiomic features in patients treated with focal salvage HDR prostate brachytherapy for local recurrence after previous external-beam radiotherapy

PURPOSE

To explore the changes in T2-weighted (T2w) and apparent diffusion coefficient (ADC) magnetic resonance imaging -derived radiomic features of the gross tumor volume (GTV) from focal salvage high-dose-rate prostate brachytherapy (HDRB) and to correlate with clinical parameters.

MATERIALS AND METHODS

Eligible patients included those with biopsy-confirmed local recurrence that correlated with MRI (T2w, ADC). Patients received 27 Gy in 2 fractions separated by 1 week to a quadrant consisting of the GTV. The MRI was repeated 1 year after HDRB. GTVs, planning target volumes, and normal prostate tissue control volumes were identified on the pre- and post-HDRB MRIs. Radiomic features from each GTV were extracted, and principle component analysis identified features with the highest variance.

RESULTS

Pre- and post-HDRB MRIs were obtained from 14 trial patients. Principle component analysis showed that 18 and 17 features contributed to 93% and 86% of the variance observed in the T2w and ADC data, respectively. Sixteen T2w features and 1 ADC GTV feature were different from the control volumes in the pre-HDRB images (p < 0.05). Ten T2w and 7 ADC GTV post-HDRB features were different from those of pre-HDRB (p < 0.05).

CONCLUSIONS

Exploratory analysis reveals several radiomic features in the T2w and ADC image GTVs that distinguish the GTV from healthy prostate tissue and change significantly after salvage HDRB.

The current state of randomized clinical trial evidence for prostate brachytherapy

Interstitial brachytherapy is one of several curative therapeutic options for the treatment of localized prostate cancer. In this review, we summarize all available randomized data to support the optimal use of prostate brachytherapy. Evidence from completed randomized controlled trials is the focus of this review with a presentation also of important ongoing trials. Gaps in knowledge are identified where future investigation may be fruitful with intent to inspire well-designed prospective studies with standardized treatment that focuses on improving oncological outcomes, reducing morbidity, or maintaining quality of life.

Focal Salvage Treatment of Radiorecurrent Prostate Cancer: A Narrative Review of Current Strategies and Future Perspectives

Over the last decades, primary prostate cancer radiotherapy saw improving developments, such as more conformal dose administration and hypofractionated treatment regimens. Still, prostate cancer recurrences after whole-gland radiotherapy remain common, especially in patients with intermediate- to high-risk disease. The vast majority of these patients are treated palliatively with androgen deprivation therapy (ADT), which exposes them to harmful side-effects and is only effective for a limited amount of time. For patients with a localized recurrent tumor and no signs of metastatic disease, local treatment with curative intent seems more rational. However, whole-gland salvage treatments such as salvage radiotherapy or salvage prostatectomy are associated with significant toxicity and are, therefore, uncommonly performed. Treatments that are solely aimed at the recurrent tumor itself, thereby better sparing the surrounding organs at risk, potentially provide a safer salvage treatment option in terms of toxicity. To achieve such tumor-targeted treatment, imaging developments have made it possible to better exclude metastatic disease and accurately discriminate the tumor. Currently, focal salvage treatment is being performed with different modalities, including brachytherapy, cryotherapy, high-intensity focused ultrasound (HIFU), and stereotactic body radiation therapy (SBRT). Oncologic outcomes seem comparable to whole-gland salvage series, but with much lower toxicity rates. In terms of oncologic control, these results will improve further with better understanding of patient selection. Other developments, such as high-field diagnostic MRI and live adaptive MRI-guided radiotherapy, will further improve precision of the treatment.