High dose-rate brachytherapy in the treatment of prostate cancer

Is Ultrahypofractionated Whole Pelvis Radiation Therapy (WPRT) as Well Tolerated as Conventionally Fractionated WPRT in Patients With Prostate Cancer? Early Results From the HOPE Trial

OBJECTIVE

The aim of this work was to evaluate the acute toxicity and quality-of-life (QOL) impact of ultrahypofractionated whole pelvis radiation therapy (WPRT) compared with conventional WPRT fractionation after high-dose-rate prostate brachytherapy (HDR-BT).

METHODS AND MATERIALS

The HOPE trial is a phase 2, multi-institutional randomized controlled trial of men with prostate-confined disease and National Comprehensive Cancer Network unfavorable intermediate-, high-, or very-high-risk prostate cancer. Patients were randomly assigned to receive conventionally fractionated WPRT (standard arm) or ultrahypofractionated WPRT (experimental arm) in a 1:1 ratio. All patients underwent radiation therapy with 15 Gy HDR-BT boost in a single fraction followed by WPRT delivered with conventional fractionation (45 Gy in 25 daily fractions or 46 Gy in 23 fractions) or ultrahypofractionation (25 Gy in 5 fractions delivered on alternate days). Acute toxicities measured during radiation therapy and at 6 weeks posttreatment were assessed using the clinician-reported Common Terminology Criteria for Adverse Events version 5.0, and QOL was measured using the Expanded Prostate Cancer Index Composite (EPIC-50) and International Prostate Symptom Score (IPSS).

RESULTS

A total of 80 patients were enrolled and treated across 3 Canadian institutions, of whom 39 and 41 patients received external radiation therapy with conventionally fractionated and ultrahypofractionated WPRT, respectively. All patients received androgen deprivation therapy except for 2 patients treated in the ultrahypofractionated arm. The baseline clinical characteristics of the 2 arms were similar, with 51 (63.8%) patients having high or very-high-risk prostate cancer disease. Treatment was well tolerated with no significant differences in the rate of acute adverse events between arms. No grade 4 adverse events or treatment-related deaths were reported. Ultrahypofractionated WPRT had a less detrimental impact on the EPIC-50 bowel total, function, and bother domain scores compared with conventional WPRT in the acute setting. By contrast, more patients treated with ultrahypofractionated WPRT reached the minimum clinical important difference on the EPIC-50 urinary domains. No significant QOL differences between arms were noted in the sexual and hormonal domains.

CONCLUSIONS

Ultrahypofractionated WPRT after HDR-BT is a well-tolerated treatment strategy in the acute setting that has less detrimental impact on bowel QOL domains compared with conventional WPRT.

High-dose-rate Brachytherapy Monotherapy in Patients With Localised Prostate Cancer: Dose Modelling and Optimisation Using Computer Algorithms

AIMS

Interstitial high-dose-rate brachytherapy (HDR-BT) is an effective therapy modality for patients with localized prostate carcinoma. The objectives of the study were to optimise the therapy regime variables using two models: response surface methodology (RSM) and artificial neural network (ANN).

MATERIALS AND METHODS

Thirty-one studies with 5651 patients were included (2078 patients presented as low-risk, 3077 patients with intermediate-risk, and 496 patients with high-risk). A comparison of these therapy schedules was carried out using an effective biologically effective dose (BEDef) that was calculated assuming the number of treatment days and dose (D) per day. The modelling and optimization of therapy parameters (BEDef and risk level) in order to obtain the maximum biochemical free survival (BFS) were carried out by the RSM and ANN models.

RESULTS

An optimal treatment schedule (BFS = 97%) for patients presented with low-risk biochemical recurrence would be D = 26 Gy applied in one application, 2 fractions at least 6 h apart, within an overall treatment time of 1 day (BEDef = 251 Gy) by the RSM and ANN model. For patients presented with intermediate- or high-risk an optimal treatment regime (BFS = 94% and 90%, respectively) would be D = 38 Gy applied in one application, 4 fractions at least 6 h apart, with an overall treatment time of 2 days (BEDef = 279 Gy) by the RSM and ANN models.

CONCLUSIONS

The RSM and ANN models determine almost the same optimal values for the set of predicted therapy parameters that make a feasible selection of an optimal treatment regime.

Penalty weight tuning in high dose rate brachytherapy using multi-objective Bayesian optimization

Objective.Treatment plan optimization in high dose rate brachytherapy often requires manual fine-tuning of penalty weights for each objective, which can be time-consuming and dependent on the planner's experience. To automate this process, this study used a multi-criteria approach called multi-objective Bayesian optimization with q-noisy expected hypervolume improvement as its acquisition function (MOBO-qNEHVI).Approach.The treatment plans of 13 prostate cancer patients were retrospectively imported to a research treatment planning system, RapidBrachyMTPS, where fast mixed integer optimization (FMIO) performs dwell time optimization given a set of penalty weights to deliver 15 Gy to the target volume. MOBO-qNEHVI was used to find patient-specific Pareto optimal penalty weight vectors that yield clinically acceptable dose volume histogram metrics. The relationship between the number of MOBO-qNEHVI iterations and the number of clinically acceptable plans per patient (acceptance rate) was investigated. The performance time was obtained for various parameter configurations.Main results.MOBO-qNEHVI found clinically acceptable treatment plans for all patients. With increasing the number of MOBO-qNEHVI iterations, the acceptance rate grew logarithmically while the performance time grew exponentially. Fixing the penalty weight of the tumour volume to maximum value, adding the target dose as a parameter, initiating MOBO-qNEHVI with 25 parallel sampling of FMIO, and running 6 MOBO-qNEHVI iterations found solutions that delivered 15 Gy to the hottest 95% of the clinical target volume while respecting the dose constraints to the organs at risk. The average acceptance rate for each patient was 89.74% ± 8.11%, and performance time was 66.6 ± 12.6 s. The initiation took 22.47 ± 7.57 s, and each iteration took 7.35 ± 2.45 s to find one Pareto solution.Significance.MOBO-qNEHVI combined with FMIO can automatically explore the trade-offs between treatment plan objectives in a patient specific manner within a minute. This approach can reduce the dependency of plan quality on planner's experience and reduce dose to the organs at risk.

21 Gy single fraction prostate HDR brachytherapy: 5-year results of a single institution prospective pilot study

PURPOSE

To present the outcome and toxicity results of a prospective trial of 21 Gy single fraction high-dose-rate (HDR) brachytherapy for men with low- or intermediate-risk prostate cancer.

METHODS AND MATERIALS

Patients were treated according to an IRB-approved prospective study of single fraction HDR brachytherapy. Eligible patients had low- or intermediate-risk prostate cancer with tumor stage ≤ T2b, PSA ≤ 15, and Gleason score ≤ 7. Patients underwent trans-rectal ultrasound-guided trans-perineal implant of the prostate followed by single fraction HDR brachytherapy to a dose of 21 Gy. The primary endpoint was grade ≥ 2 urinary/GI toxicity rates.

RESULTS

Twenty-six patients were enrolled with a median follow up of 5.1 years and median age of 64 years. 88.5% of patients had T1 disease, 15.4% had Gleason score 6 (84.6% Gleason 7), and median pre-treatment PSA was 5.0 ng/mL. Acute and chronic grade ≥ 2 urinary toxicity rates were 38.5% and 38.5%, respectively. There were no grade ≥ 2 acute or chronic GI toxicities. Six (23.1%) patients experienced biochemical failure, six (23.1%) patients experienced radiographic local failure, and five (19.2%) patients had biopsy-proven local failure. No patients developed regional lymph node recurrence or distant metastasis. 5-year overall survival and cause-specific survival were 96.2% and 100%, respectively.

CONCLUSIONS

21 Gy single fraction HDR brachytherapy was associated with modestly higher-than-anticipated chronic urinary toxicity, as well as high biochemical and local failure rates. The results from this prospective pilot study do not support the use of this regimen in standard clinical practice.

Prostate cancer across four countries in the Middle East: a multi-centre, observational, retrospective and prognostic study

Prostate cancer (PC) is the second most prevalent cancer in males, with a steadily increasing incidence in the Middle East (ME). The aim of this study was to capture real-world data on the characteristics, disease progression, and treatment patterns among PC patients in the ME. This was a retrospective, observational, multi-centre study conducted across ten hospitals/research centers in Lebanon, Kingdom of Saudi Arabia, Iraq and Kuwait. Data were abstracted from medical records of 615 male patients who were diagnosed with PC between January 2012 and the site initiation date (December 2018-May 2019) and received at least one PC treatment/intervention. The observation period ranged between 84 and 88 months. Data were collected on demographics, clinical characteristics, time to progression to the subsequent clinical state or therapy (progression from localised/locally advanced PC to castration and to metastatic PC (metastatic castration-sensitive PC (mCSPC) or metastatic castration-resistant PC (mCRPC)), progression from mCSPC to mCRPC, and mCRPC patients' progression to first subsequent line of therapy), treatment patterns, and mortality. Most patients had localised/locally advanced PC (57.7%), followed by mCSPC (37.4%), and mCRPC (4.1%) at the time of inclusion in the study. Most patients were at tumours, nodes and metastases (TNM) stage IIIa (40.1%) or TNM stage IVb (27.8%) at study entry. Median time to metastatic disease, castration-resistance and next line therapy was 84 months (95% CI: 68-84), 41 months (95% CI: 30-56) and 7 months (95% CI: 0-41), respectively. The mortality rate was 3.6%. Disease progression was most common among patients with mCSPC (35.1%) or mCRPC (14.8%), and treatment discontinuation was most common among patients with mCRPC (36.6% treatments discontinued). The results show that most patients were at an advanced TNM stage at study entry, suggestive of a lack of awareness regarding PC. Disease progression was most common among patients with metastatic disease, reflecting the challenge of treating metastatic disease and highlighting the need for novel treatments.

Risk Modeling for Individualization of the FLAME Focal Boost Approach in External Beam Radiation Therapy for Patients With Localized Prostate Cancer

PURPOSE

The FLAME trial (NCT01168479) showed that isotoxic focal boosting to the intraprostatic lesion(s) in patients with intermediate- and high-risk prostate cancer improves 5-year disease-free survival (DFS). Although the near-minimum dose to the gross tumor volume (D98%) was associated with improved outcomes, a closer look suggested that this might not be the same for all patients. Therefore, we investigated whether risk factors that are associated with a benefit of focal boosting can be identified.

METHODS AND MATERIALS

We described the distribution of clinical characteristics and the number of high-risk factors with respect to the D98% in 526 FLAME trial patients. We used penalized Cox regression to develop a prediction model. To investigate a potential benefit in patient subgroups, we compared the model-based predictions of 5-year DFS assuming standard whole-gland radiation therapy of 77 Gy to the predictions assuming an additional focal boost with D98% of 95 Gy.

RESULTS

Patients with high-risk factors were well represented in the group of 120 patients that received D98% > 85 Gy and showed fewer recurrences compared with the group that received 77 Gy. Applying the model simulating a standard dose of 77 Gy, we predicted a high DFS for grade group (GG) 1 patients, whereas patients with high-risk characteristics appeared to show a low DFS. All risk groups showed a high level of DFS when simulating D98% of 95 Gy.

CONCLUSIONS

Our results suggest that GG 1 patients already show a low level of failure at a standard dose of 77 Gy, limiting the additional benefit of focal boosting. In contrast, patients with high-risk characteristics, especially GG 4 or 5, show a low 5-year DFS, while focal boosting might improve this substantially. This suggests that reaching a high focal boost dose may be particularly beneficial for these patients.

Estimating blurless and noise-free Ir-192 source images from gamma camera images for high-dose-rate brachytherapy using a deep-learning approach

Objective. Precise monitoring of the position and dwell time of iridium-192 (Ir-192) during high-dose-rate (HDR) brachytherapy is crucial to avoid serious damage to normal tissues. Source imaging using a compact gamma camera is a potential approach for monitoring. However, images from the gamma camera are affected by blurring and statistical noise, which impact the accuracy of source position monitoring. This study aimed to develop a deep-learning approach for estimating ideal source images that reduce the effect of blurring and statistical noise from experimental images captured using a compact gamma camera.Approach. A double pix2pix model was trained using the simulated gamma camera images of an Ir-192 source. The first model was responsible for denoising the Ir-192 images, whereas the second model performed super resolution. Trained models were then applied to the experimental images to estimate the ideal images.Main results. At a distance of 100 mm between the compact gamma camera and the Ir-192 source, the difference in full width at half maximum (FWHM) between the estimated and actual source sizes was approximately 0.5 mm for a measurement time of 1.5 s. This difference has been improved from approximately 2.7 mm without the use of DL. Even with a measurement time of 0.1 s, the ideal images could be estimated as accurately as in the 1.5 s measurements. This method consistently achieved accurate estimations of the source images at any position within the field of view; however, the difference increased with the distance between the Ir-192 source and the compact gamma camera.Significance. The proposed method successfully provided estimated images from the experimental images within errors smaller than 0.5 mm at 100 mm. This method is promising for reducing blurring and statistical noise from the experimental images, enabling precise real-time monitoring of Ir-192 sources during HDR brachytherapy.

Analytical HDR prostate brachytherapy planning with automatic catheter and isotope selection

BACKGROUND

High dose rate (HDR) brachytherapy is commonly used to treat prostate cancer. Existing HDR planning systems solve the dwell time problem for predetermined catheters and a single energy source.

PURPOSE

Additional degrees of freedom can be obtained by relaxing the catheters' pre-designation and introducing more source types, and may have a dosimetric benefit, particularly in improving conformality to spare the urethra. This study presents a novel analytical approach to solving the corresponding HDR planning problem.

METHODS

The catheter and dual-energy source selection problem was formulated as a constrained optimization problem with a non-convex group sparsity regularization. The optimization problem was solved using the fast-iterative shrinkage-thresholding algorithm (FISTA). Two isotopes were considered. The dose rates for the HDR 4140 Ytterbium (Yb-169) source and the Elekta Iridium (Ir-192) HDR Flexisource were modeled according to the TG-43U1 formalism and benchmarked accordingly. Twenty-two retrospective HDR prostate brachytherapy patients treated with Ir-192 were considered. An Ir-192 only (IRO), Yb-169 only (YBO), and dual-source (DS) plan with optimized catheter location was created for each patient with N catheters, where N is the number of catheters used in the clinically delivered plans. The DS plans jointly optimized Yb-169 and Ir-192 dwell times. All plans and the clinical plans were normalized to deliver a 15 Gy prescription (Rx) dose to 95% of the clinical treatment volume (CTV) and evaluated for the CTV D90%, V150%, and V200%, urethra D0.1cc and D1cc, bladder V75%, and rectum V75%. Dose-volume histograms (DVHs) were generated for each structure.

RESULTS

The DS plans ubiquitously selected Ir-192 as the only treatment source. IRO outperformed YBO in organ at risk (OARs) OAR sparing, reducing the urethra D0.1cc and D1cc by 0.98% (p = 2.22 ∗ 10 - 9 $p\ = \ 2.22*{10^{ - 9}}$ ) and 1.09% (p = 1.22 ∗ 10 - 10 $p\ = \ 1.22*{10^{ - 10}}$ ) of the Rx dose, respectively, and reducing the bladder and rectum V75% by 0.09 (p = 0.0023 $p\ = \ 0.0023$ ) and 0.13 cubic centimeters (cc) (p = 0.033 $p\ = \ 0.033$ ), respectively. The YBO plans delivered a more homogenous dose to the CTV, with a smaller V150% and V200% by 3.20 (p = 4.67 ∗ 10 - 10 $p\ = \ 4.67*{10^{ - 10}}$ ) and 1.91 cc (p = 5.79 ∗ 10 - 10 $p\ = \ 5.79*{10^{ - 10}}$ ), respectively, and a lower CTV D90% by 0.49% (p = 0.0056 $p\ = \ 0.0056$ ) of the prescription dose. The IRO plans reduce the urethral D1cc by 2.82% (p = 1.38 ∗ 10 - 4 $p\ = \ 1.38*{10^{ - 4}}$ ) of the Rx dose compared to the clinical plans, at the cost of increased bladder and rectal V75% by 0.57 (p = 0.0022 $p\ = \ 0.0022$ ) and 0.21 cc (p = 0.019 $p\ = \ 0.019$ ), respectively, and increased CTV V150% by a mean of 1.46 cc (p = 0.010 $p\ = \ 0.010$ ) and CTV D90% by an average of 1.40% of the Rx dose (p = 8.80 ∗ 10 - 8 $p\ = \ 8.80*{10^{ - 8}}$ ). While these differences are statistically significant, the clinical differences between the plans are minimal.

CONCLUSIONS

The proposed analytical HDR planning algorithm integrates catheter and isotope selection with dwell time optimization for varying clinical goals, including urethra sparing. The planning method can guide HDR implants and identify promising isotopes for specific HDR clinical goals, such as target conformality or OAR sparing.

The Current Trend of Radiation Therapy for Patients with Localized Prostate Cancer

A recent approach to radiotherapy for prostate cancer is the administration of high doses of radiation to the prostate while minimizing the risk of side effects. Thus, image-guided radiotherapy utilizes advanced imaging techniques and is a feasible strategy for increasing the radiation dose. New radioactive particles are another approach to achieving high doses and safe procedures. Prostate brachytherapy is currently considered as a combination therapy. Spacers are useful to protect adjacent organs, specifically the rectum, from excessive radiation exposure.

Synthesis, Characterization, and Therapeutic Efficacy of 177Lu-DMSA@SPIONs in Nanobrachytherapy of Solid Tumors

As an alternative to classical brachytherapy, intratumoral injection of radionuclide-labeled nanoparticles (nanobrachytherapy, NBT) has been investigated as a superior delivery method over an intravenous route for radionuclide therapy of solid tumors. We created superparamagnetic iron oxide nanoparticles (SPIONs) coated with meso-1,2-dimercaptosuccinic acid (DMSA) and radiolabeled with Lutetium-177 (¹⁷⁷Lu), generating ¹⁷⁷Lu-DMSA@SPIONs as a potential antitumor agent for nanobrachytherapy. Efficient radiolabeling of DMSA@SPIONS by ¹⁷⁷Lu resulted in a stable bond with minimal leakage in vitro. After an intratumoral injection to mouse colorectal CT-26 or breast 4T1 subcutaneous tumors, the nanoparticles remained well localized at the injection site for weeks, with limited leakage. The dose of 3.70 MBq/100 µg/50 µL of ¹⁷⁷Lu-DMSA@SPIONs applied intratumorally resulted in a high therapeutic efficacy, without signs of general toxicity. A decreased dose of 1.85 MBq/100 µg/50 µL still retained therapeutic efficacy, while an increased dose of 9.25 MBq/100 µg/50 µL did not significantly benefit the therapy. Histopathology analysis revealed that the ¹⁷⁷Lu-DMSA@SPIONs act within a limited range around the injection site, which explains the good therapeutic efficacy achieved by a single administration of a relatively low dose without the need for increased or repeated dosing. Overall, ¹⁷⁷Lu-DMSA@SPIONs are safe and potent agents suitable for intra-tumoral administration for localized tumor radionuclide therapy.

Application of three-dimensional multi-imaging combination in brachytherapy of cervical cancer

BACKGROUND

Three-dimensional (3D) imaging has an important role in brachytherapy and the treatment of cervical cancer. The main imaging methods used in the cervical cancer brachytherapy include magnetic resonance imaging (MRI), computer tomography (CT), ultrasound (US), and positron emission tomography (PET). However, single-imaging methods have certain limitations compared to multi-imaging. The application of multi-imaging can make up for the shortcomings and provide a more suitable imaging selection for brachytherapy.

PURPOSE

This review details the situation and scope of existing multi-imaging combination methods in cervical cancer brachytherapy and provides a reference for medical institutions.

MATERIALS AND METHODS

Searched the literature related to application of three-dimensional multi-imaging combination in brachytherapy of cervical cancer in PubMed/Medline and Web of Science electronic databases. Summarized the existing combined imaging methods and the application of each method in cervical cancer brachytherapy.

CONCLUSION

The current imaging combination methods mainly include MRI/CT, US/CT, MRI/US, and MRI/PET. The combination of two imaging tools can be used for applicator implantation guidance, applicator reconstruction, target and organs at risk (OAR) contouring, dose optimization, prognosis evaluation, etc., which provides a more suitable imaging choice for brachytherapy.

Safety and efficacy associated with single-fraction high-dose-rate brachytherapy in localized prostate cancer: a systematic review and meta-analysis

OBJECTIVE

Although single-fraction high-dose-rate brachytherapy (SFHDR) for localized prostate cancer has been tried in clinical trials, relevant medical evidence is currently lacking. It is necessary to systematically analyze the safety and efficacy of SFHDR.

METHODS

Comprehensive and systematic searches for eligible studies were performed in PubMed, Embase, and the Cochrane Library databases. The primary endpoints included safety and efficacy, represented by toxic effects and biochemical recurrence-free survival (bRFS), respectively. The proportion rates were used as the effect measure for each study and were presented with corresponding 95% confidence intervals (CI) and related 95% prediction interval (PI). Restricted maximum-likelihood estimator (REML) and the Hartung-Knapp method were used in the meta-analysis.

RESULTS

Twenty-five studies met the inclusion criteria for quantitative analysis, including 1440 patients. The median age of patients was 66.9 years old (62-73 years old) and the median follow-up was 47.5 months (12-75 months). The estimates of cumulative occurrence for severe gastrointestinal (GI) and genitourinary (GU) toxic effects were 0.1% (95% CI 0-0.2%) and 0.4% (95% CI 0-1.2%), and for grade 2 toxic effects were 1.6% (95% CI 0.1-4.7%) and 17.1% (95% CI 5.4-33.5%), respectively. The estimate of 3‑year bRFS was 87.5% (95% CI 84.4-90.3%) and 71.0% (95% CI 63.0-78.3%) for 5‑year bRFS. The pooled bRFS rates for low-risk patients were 99.0% (95% CI 85.2-100.0%) at 3 years and 80.9% (95% CI 75.4-85.9%) at 5 years, and the risk group was found to be statistically correlated with bRFS (3-year bRFS, P < 0.01; 5‑year bRFS, P = 0.04).

CONCLUSION

SFHDR is associated with favorable tolerability and suboptimal clinical benefit in patients with localized prostate cancer. Ongoing and planned high-quality prospective studies are necessary to verify its safety and efficacy.

Dose perturbation effects by metal hip prosthesis in gynaecological 192Ir HDR brachytherapy

The present study was conducted to elucidate the effects of hip prostheses in ¹⁹²Ir HDR brachytherapy and determine dose uncertainties introduced by the treatment planning. A gynaecological phantom irradiated using Nucletron ¹⁹²Ir microSelectron HDR source was modeled using MCNP5 code. Three hip materials considered in this study were water, bone, and metal prosthesis. According to the obtained results, a dose perturbation was observed within the medium with a higher atomic number, which reduced the dose to the nearby region.

Comparison between MCNP and planning system in brachytherapy of cervical cancer

Absorbed doses in uterus during brachytherapy were calculated with MCNP in relevant points and compared with planning system for one patients. MCNP was applied with two different humanoid phantoms in input, ORNL and voxel models, which represent human body in mathematical way. Good agreement between both phantoms, as well as, between MCNP and planning system were found. In addition the doses in critical organs (bladder and colon in this kind of therapy), were calculated and compared with maximal doses in these organs obtained from planning system for 15 other patients. MCNP doses agree well with planning system in points of uterus for those 15 patients, where radioactive source is used to apply. However, there are systematical discrepancies between doses in colon and bladder obtained by MCNP and planning system.

Feasibility of online adaptive HDR prostate brachytherapy: A novel treatment concept

PURPOSE

The purpose of this study was to determine the feasibility of online adaptive transrectal ultrasound (TRUS)-based high-dose-rate prostate brachytherapy (HDRPBT) through retrospective simulation of source positioning and catheter swap errors on patient treatment plans.

METHOD

Source positioning errors (catheter shifts in 1 mm increments in the cranial/caudal, anterior/posterior, and medial/lateral directions up to ±6 mm) and catheter swap errors (between the most and least heavily weighted) were introduced retrospectively into DICOM treatment plans of 20 patients that previously received TRUS HDRPBT. Dose volume histogram (DVH) indices were monitored as errors were introduced sequentially into individual catheters, simulating potential errors throughout treatment. Whenever DVH indices were outside institution thresholds: prostate V100% <95%, urethra D0.1cc >118% and rectum Dmax >80%, the plan was adapted using remaining catheters (i.e., simulating previous catheters as previously delivered). The final DVH indices were recorded.

RESULTS

Prostate coverage (V100% >95%) could be maintained for source position errors up to 6 mm through online plan adaptation. The source position error at which the urethra D0.1cc and rectum Dmax was able to return to clinically acceptable levels using online adaptation varied between 6 mm to 1 mm, depending on the direction of the source position error and patient anatomy. After introduction of catheter swap errors to patient plans, prostate V100% was recoverable using online adaptation to near original plan characteristics. Urethra D0.1cc and rectum Dmax showed less recoverability.

CONCLUSION

Online adaptive HDRPBT maintains the prostate V100% to clinically acceptable values for majority of directional shifts. However, the current online adaptive method may not correct for source position errors near organs at risk.

HDR Brachytherapy Planning using Active Needles - Preliminary Investigation on Dose Planning

In this study we present a new approach to plan a high-dose-rate (HDR) prostate brachytherapy (BT) using active needles recently developed by our group. The active needles realize bi-directional bending inside the tissue, and thereby more compliant with the patient's anatomy compared with conventional straight needles. A computational method is presented to first generate a needle arrangement configuration based on the patient's prostate anatomy. The needle arrangement is generated to cover the prostate volume, providing accessible channels for the radiation source during a HDR BT. The needle arrangement configuration avoids healthy organs and prevents needle collision inside the body. Then a treatment plan is proposed to ensure sufficient prescribed dosage to the whole prostate gland. The method is applied to a prostate model reconstructed from an anonymized patient to show the feasibility of this method. Finally, the active needle's capability to generate the required bending is shown. We have shown that our method is able to automatically generate needle arrangement configuration using active needles, and plan for a treatment that meets the dose objectives while using fewer needles (about 20% of conventional straight needles) than the conventional HDR BT performed by straight needles.

Implementation of High-Dose-Rate, CT-Based Prostate Brachytherapy in an Academic Teaching Hospital and Residency Training Program

Introduction

Prostate brachytherapy provides the most durable local control for prostate adenocarcinoma among all radiation treatment options. However, likely due to decreased trainee familiarity with the technique and resource intensity, it has seen a decline in utilization. Here we outline our experience with starting a high-dose-rate (HDR) prostate brachytherapy program within a residency training program and present our outcome data.

Methods

Patients were identified and screened using clinical data and volume study for candidacy for brachytherapy implantation. Eligible candidates were implanted and subsequently had radiation planning and delivery in our clinic. Descriptive statistical analysis was performed on our outcomes and dosimetry data and presented in tabular form.

Results

Seventeen patients were treated for a total of 18 implants (one monotherapy). No implant was aborted. No acute urinary retention requiring catheterization or chronic urethral stricture occurred. Biochemical recurrence-free survival was 94% at a median follow-up of 28.5 months (range 8.2-50 months); the one failure occurred in a very high-risk patient at 37 months following treatment. Dosimetrically, prostate coverage, urethra sparing, and rectum sparing aims were met. Volumetric bladder aims were also met; however, the max point dose to the bladder neck was above the guideline.

Conclusion

Our department successfully implemented an HDR prostate brachytherapy program. Treatments were effective and there was no grade 3 toxicity to report.

Prostate cancer brachytherapy: SFRO guidelines 2021

Prostate brachytherapy techniques are described, concerning both permanent seed implant and high dose rate brachytherapy. The following guidelines are presented: brachytherapy indications, implant procedure for permanent low dose rate implants and high dose rate with source projector, as well as dose and dose-constraints objectives, immediate postoperative management, post-treatment evaluation, and long-term follow-up.

Feasibility of fusing three-dimensional transabdominal and transrectal ultrasound images for comprehensive intraoperative visualization of gynecologic brachytherapy applicators

PURPOSE

In this study, we propose combining three-dimensional (3D) transrectal ultrasound (TRUS) and 3D transabdominal ultrasound (TAUS) images of gynecologic brachytherapy applicators to leverage the advantages of each imaging perspective, providing a broader field-of-view and allowing previously obscured features to be recovered. The aim of this study was to evaluate the feasibility of fusing these 3D ultrasound (US) perspectives based on the applicator geometry in a phantom prior to clinical implementation.

METHODS

In proof-of-concept experiments, 3D US images of application-specific multimodality pelvic phantoms were acquired with tandem-and-ring and tandem-and-ovoids applicators using previously validated imaging systems. Two TRUS images were acquired at different insertion depths and manually fused based on the position of the ring/ovoids to broaden the TRUS field-of-view. The phantom design allowed "abdominal thickness" to be modified to represent different body habitus and TAUS images were acquired at three thicknesses for each applicator. The merged TRUS images were then combined with TAUS images by rigidly aligning applicator components and manually refining the registration using the positions of source channels and known tandem length, as well as the ring diameter for the tandem-and-ring applicator. Combined 3D US images were manually, rigidly registered to images from a second modality (magnetic resonance (MR) imaging for the tandem-and-ring applicator and X-ray computed tomography (CT) for the tandem-and-ovoids applicator (based on applicator compatibility)) to assess alignment. Four spherical fiducials were used to calculate target registration errors (TREs), providing a metric for validating registrations, where TREs were computed using root-mean-square distances to describe the alignment of manually identified corresponding fiducials. An analysis of variance (ANOVA) was used to identify statistically significant differences (p < 0.05) between the TREs for the three abdominal thicknesses for each applicator type. As an additional indicator of geometric accuracy, the bladder was segmented in the 3D US and corresponding MR/CT images, and volumetric differences and Dice similarity coefficients (DSCs) were calculated.

RESULTS

For both applicator types, the combination of 3D TRUS with 3D TAUS images allowed image information obscured by the shadowing artifacts under single imaging perspectives to be recovered. For the tandem-and-ring applicator, the mean ± one standard deviation (SD) TREs from the images with increasing thicknesses were 1.37 ± 1.35 mm, 1.84 ± 1.22 mm, and 1.60 ± 1.00 mm. Similarly, for the tandem-and-ovoids applicator, the mean ± SD TREs from the images with increasing thicknesses were 1.37 ± 0.35 mm, 1.95 ± 0.90 mm, and 1.61 ± 0.76 mm. No statistically significant difference was detected in the TREs for the three thicknesses for either applicator type. The mean volume differences for the bladder segmentations were 3.14% and 2.33% and mean DSCs were 87.8% and 87.7% for the tandem-and-ring and tandem-and-ovoids applicators, respectively.

CONCLUSIONS

In this proof-of-concept study, we demonstrated the feasibility of fusing 3D TRUS and 3D TAUS images based on the geometry of tandem-and-ring and tandem-and-ovoids applicators. This represents a step toward an accessible and low-cost 3D imaging method for gynecologic brachytherapy, with the potential to extend this approach to other intracavitary configurations and hybrid applicators.

Multipurpose ultrasound-based prostate phantom for use in interstitial brachytherapy

PURPOSE

While brachytherapy is an effective treatment for localized prostate cancer, there has been a noticeable decline in its use. Training opportunity for prostate brachytherapy has been in steady decline, with some residents receiving little to no hands-on training. This work was developed to design a training environment that uses a phantom-based simulator to teach the process of TRUS-based prostate brachytherapy METHODS AND MATERIALS: A prostate phantom was fabricated from a representative prostate patient TRUS scan. Three materials were used: gelatin powder, graphite powder, and water. The prostate was developed using 9% gelatin and 0.3% graphite per 100 ml water. Five radiation oncologists were asked to qualitatively score the phantom according to image quality, haptic feedback, needle insertion quality, and its compatibility with operative tools. The contrast-to-noise ratio (CNR) was estimated using different concentrations of graphite. The elasticity of the phantom was evaluated based on ultrasound elastography measurements RESULTS: The prostate phantom had an average CNR of 3.94 ± 1.09 compared to real prostate images with a CNR of 2 ± 1.8. The average Young's modulus was computed to be 58.03 ± 6.24 kPa compared to real prostate tissue (58.8 ± 8.2 kPa). Oncologists ranked the phantom as "very good" for overall quality of the phantom. They reported that needle insertion quality was "very good" during a simulated brachytherapy procedure.

CONCLUSION

We have developed a 3D printing prostate phantom to be used for training purposes during prostate brachytherapy. The phantom has been evaluated for image quality and elasticity. The reconstructed phantom could be used as an anthropomorphic surrogate to train residents on prostate brachytherapy procedures.

Utilization of brachytherapy in Quebec, Canada

BACKGROUND AND PURPOSE

Despite the excellent clinical outcomes from brachytherapy treatments compared with other modalities and the low associated costs, there have been reports of a decline in utilization of brachytherapy. The aim of this study was to investigate in detail the trend in utilization of brachytherapy in the province of Québec, Canada, from 2011 to 2019.

MATERIALS AND METHODS

All radiotherapy clinics in the province of Quebec, and among these the clinics that provide brachytherapy treatments, were identified. This observational retrospective cohort study involved analysis of data compiled by the Ministère de la Santé et des Services Sociaux du Québec for the period of 2011 to end of 2019 on all brachytherapy procedures performed in the province of Quebec. Time series graphs were used to describe the number of high dose rate (HDR) and low dose rate (LDR) brachytherapy treatments during the studied time period. Statistical analysis was conducted using R statistical software.

RESULTS

Between 2011 and 2019, 12 hospitals in the province of Québec provided radiotherapy treatments, and all of them offered brachytherapy services. The median annual number of brachytherapy sessions was 4413 (range 3930-4829). HDR brachytherapy represented over 90% of all brachytherapy treatments throughout the study period. Significant changes over time were observed in the number of treatments: at least 5% change was seen only for the two most common subtypes of brachytherapy, HDR interstitial and HDR intracavitary, with an increase of 9.6% and a decrease of 9.2%, respectively. The use of other subtypes of brachytherapy (HDR-plesiotherapy, LDR-interstitial, LDR-intracavitary, LDR-eye plaque) was stable between 2011 and 2019, with ≤ 2.5% variation.

CONCLUSION

This study demonstrates an overall steady use of brachytherapy between 2011 and 2019 in Quebec. Brachytherapy offers numerous advantages for the treatment of diverse cancer sites. Although more sophisticated external beam radiotherapy treatments have emerged in the last decades, the precision and cost-effectiveness of brachytherapy remain unbeaten. To ensure the continued use and availability of brachytherapy, governments must put in place policies and regulations to that effect. Training and exposure of future health care professionals to brachytherapy within Quebec and Canada is essential to provide all patients the same access to this life saving modality.

MRI-TRUS registration methodology for TRUS-guided HDR prostate brachytherapy

Purpose

High‐dose‐rate (HDR) prostate brachytherapy is an established technique for whole‐gland treatment. For transrectal ultrasound (TRUS)‐guided HDR prostate brachytherapy, image fusion with a magnetic resonance image (MRI) can be performed to make use of its soft‐tissue contrast. The MIM treatment planning system has recently introduced image registration specifically for HDR prostate brachytherapy and has incorporated a Predictive Fusion workflow, which allows clinicians to attempt to compensate for differences in patient positioning between imaging modalities. In this study, we investigate the accuracy of the MIM algorithms for MRI‐TRUS fusion, including the Predictive Fusion workflow.

Materials and Methods

A radiation oncologist contoured the prostate gland on both TRUS and MRI. Four registration methodologies to fuse the MRI and the TRUS images were considered: rigid registration (RR), contour‐based (CB) deformable registration, Predictive Fusion followed by RR (pfRR), and Predictive Fusion followed by CB deformable registration (pfCB). Registrations were compared using the mean distance to agreement and the Dice similarity coefficient for the prostate as contoured on TRUS and the registered MRI prostate contour.

Results

Twenty patients treated with HDR prostate brachytherapy at our center were included in this retrospective evaluation. For the cohort, mean distance to agreement was 2.1 ± 0.8 mm, 0.60 ± 0.08 mm, 2.0 ± 0.5 mm, and 0.59 ± 0.06 mm for RR, CB, pfRR, and pfCB, respectively. Dice similarity coefficients were 0.80 ± 0.05, 0.93 ± 0.02, 0.81 ± 0.03, and 0.93 ± 0.01 for RR, CB, pfRR, and pfCB, respectively. The inclusion of the Predictive Fusion workflow did not significantly improve the quality of the registration.

Conclusions

The CB deformable registration algorithm in the MIM treatment planning system yielded the best geometric registration indices. MIM offers a commercial platform allowing for easier access and integration into clinical departments with the potential to play an integral role in future focal therapy applications for prostate cancer.

MR compatibility, safety and accuracy of the redesigned UMC Utrecht single needle implant device

Purpose. The Utrecht single needle implant device (SNID) was redesigned to increase needle insertion velocity. The purpose of this study is to evaluate the magnetic resonance compatibility, safety and accuracy of the implant device preparing its application in a patient study to investigate the feasibility of inserting a brachytherapy needle into the prostate to a defined tumor target point.Methods. Several experiments were performed to evaluate the mechanical and radiofrequency safety of the needle system, the magnetic field perturbation, the calibration of the implant device in the MR coordinate system, functioning of the implant device during imaging and accuracy of needle insertion.Results. Endurance experiments showed the mechanical safety of the needle system. Magnetic field perturbation was acceptable with induced image distortions smaller than 0.5 mm for clinical MR sequences. Calibration of the implant device in the MR coordinate system was reproducible with average error (mean±standard deviation) of 0.2 ± 0.4 mm, 0.1 ± 0.3 mm and 0.6 ± 0.6 mm in thex,y- andz- direction, respectively. The RF safety measurement showed for clinical MR imaging sequences maximum temperature rises of 0.2 °C at the entry and tip points of the needle. Simultaneous functioning of the implant device and imaging is possible albeit with some intensity band artifacts in the fast field echo images. Finally, phantom measurements showed deviations amounting 2.5-3.6 mm measured as target-to-needle distance at a depth of 12 cm.Conclusions. This preclinical evaluation showed that the MR compatibility, safety and accuracy of the redesigned UMC Utrecht SNID allow its application in a patient study on the feasibility of inserting a brachytherapy needle into the prostate to a defined tumor target point.

High-dose-rate brachytherapy as monotherapy for low- and intermediate-risk prostate cancer: long-term experience of Swedish single-center

Purpose

Until now, most long-term results for brachytherapy only has been published for low-dose-rate (LDR) seeds. Due to radiobiology reasons, high-dose-rate (HDR) mono-brachytherapy is of growing interest. The aim of the study was to report long-term biochemical control rate and toxicities with HDR monotherapy.

Material and methods

This was a retrospective single-institution experience, including 229 men, clinically staged T1c-T2b, Gleason 3 + 3 (prostate specific antigen (PSA) ≤ 15), or Gleason 3 + 4 (PSA ≤ 10), consecutively treated between 2004 and 2012 with HDR brachytherapy alone, using three different fractionation schedules of 92-95 Gy (EQD(2), α/β = 3). Group 4F (n = 19) had a single implant of 9.5 Gy in four fractions over 2 days. Group 3F (n = 107) had three separate implants of 11 Gy over 4 weeks. Group 2F (n = 103) had two implants of 14 Gy over 2 weeks. No adjuvant hormonal therapy was allowed.

Results

For 4F, 3F, and 2F study groups, median follow-up was 10.2, 7.1, and 6.1 years, respectively, and biochemical failure rate was 10.5%, 4.7%, and 14.6%, respectively. Early and late side effects were followed with common terminology criteria version 2.0 and patient-reported questionnaires. There were a temporary acute urethral toxicity increase, 1-2 grades over baseline lower urinary tract symptoms (LUTS), which usually recovered. About 1/3 of the patients had a remaining one grade over baseline LUTS. Severe grade 3-4 toxicity were only found in 3.5% of patients. No rectal toxicity was observed. Erectile dysfunction (ED) was depending on age and erectile function before treatment. In patients without ED before the treatment, we found a complete ED in 21% of men at the last follow-up.

Conclusions

In the present study, HDR mono-brachytherapy was found to be an effective treatment, with mild long-term side effects difficult to differentiate from aging effects. There were no significant differences in PSA regression, PSA failure rate, and toxicity between the different fraction schedules.

Trimodal therapy with high-dose-rate brachytherapy and hypofractionated external beam radiation combined with long-term androgen deprivation for unfavorable-risk prostate cancer

Purpose

To assess the outcomes of high-dose-rate (HDR) brachytherapy and hypofractionated external beam radiation therapy (EBRT) combined with long-term androgen deprivation therapy (ADT) in very-high-risk (VHR) versus high-risk (HR) prostate cancer (PCa), as defined in the National Comprehensive Cancer Network (NCCN) criteria.

Methods

Data from 338 consecutive HR or VHR PCa patients who had undergone this tri-modal therapy between 2005 and 2018 were retrospectively analyzed. Biochemical recurrence (BCR)-free, progression-free, overall, and cancer-specific survival (BCRFS/PFS/OS/CSS) rates were analyzed using the Kaplan–Meier method and Wilcoxon test. Cox regression models were used to evaluate candidate prognostic factors for survival. C‑indexes were used to assess model discrimination.

Results

Within a median follow-up of 84 months, 68 patients experienced BCR, 58 had disease progression including only 3 with local progression, 27 died of any cause, and 2 died from PCa. The 5‑year BCRFS, PFS, OS, and CSS rates were 82.2% (HR 86.5%; VHR 70.0%), 90.0% (HR 94.3%; VHR 77.6%), 95.7% (HR, 97.1%; VHR, 91.8%), and 99.6% (HR, 100%; VHR, 98.0%), respectively. In multivariable analyses that adjusted for standard clinicopathologic features, the risk subclassification was associated both PFS and OS (p = 0.0003 and 0.001, respectively). Adding the risk subclassification improved the accuracy of models in predicting BCRFS, PFS, and OS.

Conclusion

While the outcome of this trimodal approach appears favorable, VHR PCa patients had significantly worse oncological outcomes than those with HR PCa. The NCCN risk subclassification should be integrated into prognostic tools to guide risk stratification, treatment, and follow-up for unfavorable PCa patients receiving this trimodal therapy.

Supplementary Information

The online version of this article (10.1007/s00066-021-01784-3) contains supplementary material, which is available to authorized users.

Low-/high-dose-rate brachytherapy boost in patients with intermediate-risk prostate cancer treated with radiotherapy: long-term results from a single institution team experience

Purpose

To compare brachytherapy (BT) boost of low-dose-rate (LDR) and high-dose-rate (HDR) techniques in patients diagnosed with intermediate-risk prostate cancer.

Material and methods

Between January 2005 and February 2018, 142 patients (50 LDR and 92 HDR) with intermediate-risk prostate cancer were treated with a BT boost, and retrospectively analyzed. Prescribed dose was 45 Gy with external beam radiotherapy (EBRT) plus 100-108 Gy with LDR-BT, and 60 Gy with EBRT plus one fraction of 10 Gy with HDR-BT. 99% of patients received androgen deprivation therapy (ADT) for 6 months. Primary endpoint was to compare LDR and HDR boosts in terms of biochemical progression-free survival (bPFS). Secondary endpoint, after re-classifying patients into "favorable" and "unfavorable" sub-groups, was to analyze differences with a similar treatment intensity.

Results

Median overall follow-up for the total cohort was 66.5 months (range, 16-185 months). There were no significant differences in bPFS, overall survival, cause specific survival, local failure, lymph node failure, or distant failure when LDR or HDR was employed. bPFS at 90 months was 100% for favorable, and 89% and 85% for unfavorable patients at 60 months and 90 months, respectively (log-rank test, p = 0.017). The crude incidence of genitourinary acute and chronic toxicity grade 3 was 0.7% and 4%, respectively. Twelve patients (8%) had chronic rectal hemorrhage grade 2, in whom argon was applied (4 LDR and 8 HDR).

Conclusions

Combined treatment is an excellent therapeutic option in patients with intermediate-risk prostate carcinoma, with similar results in both LDR and HDR approaches and very low toxicities. Importantly, the current literature has indicated that unfavorable-risk patients belong to a different category, and should be treated as patients with high-risk factors. Therefore, the stratification and identification of both risk groups is extremely relevant.

Complications and side effects of high-dose-rate prostate brachytherapy

PURPOSE

To describe technical challenges and complications encountered during and after high-dose-rate prostate brachytherapy (HDR-BT) and review management of these complications.

METHODS AND MATERIALS

The authors performed a systematic review of the literature on toxicities encountered after prostate HDR-BT +/- external beam radiotherapy. A total of 397 studies were identified, of which 64 were included. A focused review of literature regarding the management of acute and late toxicities also performed.

RESULTS

Most acute toxicities include grade 0-2 genitourinary and gastrointestinal toxicity. Overall, Grade 3+ Common Terminology Criteria for Adverse Events toxicity after HDR-BT was low [genitourinary: 0-1%; gastrointestinal 0-3%]. Rates of fistula formation were <1%, and radiation cystitis/proctitis were <14% and more commonly reported in cohorts treated with HDR-BT boost and external beam radiotherapy.

CONCLUSIONS

HDR-BT both as monotherapy or combined with external beam radiotherapy for prostate cancer is well tolerated. Serious complications are rare.

Use of deformable image registration techniques to estimate dose to organs at risk following prostate external beam radiation therapy and high-dose-rate brachytherapy

PURPOSE

The purpose of this investigation was to examine differences in estimates of accumulated rectal dose when using deformable image registration (DIR) compared with rigid image registration (RIR) methods, and parameter addition methods for combined transrectal ultrasound (TRUS)-based high-dose-rate brachytherapy (HDR-BT) and external beam radiation therapy (EBRT) treatments of prostate cancer.

MATERIAL AND METHODS

In this retrospective study, data from 10 patients who had previously received HDR-BT in one 15 Gy fraction, followed by 46 Gy EBRT in twenty-three fractions were used. To estimate total combined dose to the rectum, dose accumulation using both DIR and RIR methods were compared with parameter addition methods, which assume the same region of rectal anatomy receives the maximum dose from both treatment modalities. For both rigid and deformable image registration techniques, the quality of image registration was evaluated through metrics, including mean distance to agreement and dice similarity coefficient of prostate contours. Total D1cc and D2cc for the rectum was calculated and compared using each method.

RESULTS

The parameter addition methods predicted the highest accumulated dose to the rectum. On average, the predicted D2cc dose was higher than that calculated by the DIR method by 6.59 Gy EQD2 (range, -3.03 to 13.68 Gy EQD2) for partial parameter addition (PPA), and 4.88 Gy EQD2 (range, -3.41 to 11.97 Gy EQD2) for the full parameter addition (FPA) methods. Similarly, RIR predicted higher average doses compared with DIR, with a difference of 3.46 Gy EQD2 (range, -5.50 to 7.90 Gy EQD2). The results showed a significant difference between DIR and parameter addition methods for dose estimation.

CONCLUSIONS

This retrospective study demonstrates significant differences in accumulated rectal dose prediction using different image registration methods. Each method has limitations in its application, and when used with real-time HDR-BT dose planning, awareness of these limitations is essential.

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.

Long-Term Results of Moderate Hypofractionation to Prostate and Pelvic Nodes Plus Androgen Suppression in High-Risk Prostate Cancer

PURPOSE

Moderate hypofractionated radiation therapy (HypoRT) is an attractive alternative to conventionally fractionated radiation therapy for prostate cancer. However, most studies using HypoRT only included the prostate as the target volume. We report long-term outcomes of patients with high-risk prostate cancer treated with androgen deprivation therapy (ADT) and HypoRT to the prostate and nodal areas with a simultaneous integrated boost technique.

METHODS AND MATERIALS

Patients with localized, high-risk prostate cancer entered a prospective phase I/II study with a HypoRT regimen of 60 Gy/20 fractions (4 weeks) to the prostate volume while the nodal areas received 44 Gy in the same 20 fractions delivered with intensity modulated radiation therapy with a simultaneous integrated boost technique. ADT started 2 to 3 months before HypoRT. Toxicity was prospectively assessed according to the Common Terminology Criteria for Adverse Events v3. Outcomes rates were calculated by the actuarial method of Kaplan-Meier from the date of last radiation treatment until date of event.

RESULTS

We report on the first 105 patients treated between October 2010 and February 2014. Median follow-up was 74 months, with 97% of patients followed for more than 36 months. Median ADT duration was 18 months. The worst grade 2 or higher late gastrointestinal or genitourinary toxicity was seen in 7% and 9%, respectively. There was no grade 4 or 5 toxicity. At the last follow-up, the rates of grade ≥2 gastrointestinal or genitourinary toxicity were 2% and 3%, respectively, with no residual grade ≥3 toxicity. The 5- and 7-year actuarial overall survival and relapse free survival were 91% and 85% and 87% and 81%, respectively.

CONCLUSIONS

The longest follow-up report of moderate HypoRT (plus ADT) to the prostate and pelvic nodes shows that this approach is feasible, well tolerated, and effective. It is convenient for patients and the health system. A larger randomized trial using this approach is warranted.

Epidemiology, Staging and Management of Prostate Cancer

Prostate cancer is the second most common and fifth most aggressive neoplasm among men worldwide. It is particularly incident in high human development index (HDI) nations, with an estimated one in seven men in the US receiving a prostate cancer diagnosis in their lifetime. A rapid rise and then fall in prostate cancer incidence in the US and Europe corresponded to the implementation of widespread prostate specific antigen (PSA) testing in 1986 and then subsequent fall from favor due to high rates of false positives, overdiagnosis, and overtreatment (as many as 20-50% of men diagnosed could have remained asymptomatic in their lifetimes). Though few risk factors have been characterized, the best known include race (men of African descent are at higher risk), genetics (e.g., BRCA1/2 mutations), and obesity. The Gleason scoring system is used for histopathological staging and is combined with clinical staging for prognosis and treatment. National guidelines have grown more conservative over the past decades in management, recommending watchful waiting and observation in older men with low to intermediate risk disease. Among higher risk patients, prostatectomy (robotic is preferred) and/or external beam radiotherapy is the most common interventions, followed by ADT maintenance. Following progression on androgen deprivation therapy (ADT) (known as castration-resistance), next generation endocrine therapies like enzalutamide, often in combination with cytotoxic agent docetaxel, are standard of care. Other promising treatments include Radium-223 for bone metastases, pembrolizumab for programmed death ligand-1 (PDL1) and microsatellite instability (MSI) high disease, and poly ADP ribose polymerase (PARP) inhibitors for those with mutations in homologous recombination (most commonly BRCA2).

Overall survival comparison between androgen deprivation therapy (ADT) plus external beam radiation therapy (EBRT) vs ADT plus EBRT with brachytherapy boost in clinically node-positive prostate cancer

PURPOSE

Optimal therapy for clinically node-positive, nonmetastatic (cN1) prostate cancer (PC) patients remains controversial, ranging from aggressive local therapy to palliative systematic therapy alone. Despite guideline support, it is unclear if a brachytherapy (BT) boost should be considered for cN1 patients as these patients were excluded from randomized trials establishing its benefit. Herein, we compare definitive radiation therapy (RT) with or without a BT boost in cN1 PC.

METHODS AND MATERIALS

The National Cancer Database was used to identify men with cN1 PC treated with definitive RT and concomitant androgen deprivation therapy between 2004 and 2013. Overall survival (OS) was compared between those who received external beam RT (EBRT) or combination EBRT plus BT boost (EBRT + BT) using Kaplan-Meier with propensity score matching and Cox proportional hazards.

RESULTS

With a median followup of 48.5 months, 1,650 patients were eligible for this analysis, 103 (6.2%) of whom received EBRT + BT. Younger age, no medical comorbidities, and Gleason score of six were associated with higher likelihood of receiving EBRT + BT over EBRT alone. The mean (median) OS for EBRT and EBRT + BT was 99.0 (110.6) months vs 109.2 (not reached) months, respectively (p = 0.048). However, no significance difference in OS was observed between the groups after propensity score matching. On multivariable analysis, EBRT + BT was not significantly associated with improved OS (adjusted HR 0.67, 95% CI, 0.41-1.07, p = 0.098).

CONCLUSIONS

In this retrospective, observational study of patients with cN1 PC treated with definitive RT and concomitant androgen deprivation therapy, EBRT + BT had an unadjusted improvement in OS compared with EBRT alone that lost statistical significance after multivariable adjustment and propensity score matching.

Building a High-Dose-Rate Prostate Brachytherapy Program With Real-Time Ultrasound-Based Planning: Initial Safety, Quality, and Outcome Results

Purpose

Growing evidence supports the efficacy and safety of high-dose-rate (HDR) brachytherapy as a boost or monotherapy in prostate cancer treatment. We initiated a new HDR prostate brachytherapy practice in April 2014. Here, we report the learning experiences, short-term safety, quality, and outcome.

Methods and Materials

From April 2014 to December 2017, 164 men were treated with HDR brachytherapy with curative intent. Twenty-eight men (17.1%) underwent HDR brachytherapy as monotherapy, receiving 25 to 27 Gy in 2 fractions. Men treated with HDR brachytherapy as a boost received 19 to 21 Gy in 2 fractions. Fifty-two men (31.7%) had high-risk disease. HDR procedure times, dosimetry, and response were recorded and analyzed. Genitourinary (GU) and gastrointestinal (GI) toxicities were recorded according to the toxicity criteria of the Radiation Therapy Oncology Group.

Results

Mean HDR procedure times decreased yearly from 179 minutes in 2014 to 115 minutes in 2017. Median follow-up was 18.6 months (range, 3-55 months). At last review, 79% of patients reported returning to baseline GU status, and 100% of patients noted no change in GI status from their baseline. Four patients experienced acute urinary retention. Treatment planning target volume (PTV) was defined as prostate with margins. Dosimetrically, 97.5% of all HDR implants had PTV D90 ≥100%, 81.5% had PTV V100 ≥95%, 73.6% had maximal urethral doses ≤120%, and 77.5% had rectal 1 mL dose ≤70% (all but one ≤10.8 Gy). The estimated 3-year overall survival was 98.7% (95% confidence interval, 91.4%-99.8%), and disease-free survival was 96.2% (95% confidence interval, 89.5%-98.7%).

Conclusions

The low incidence of GU and GI complications in our cohort demonstrates that a HDR brachytherapy program can be successfully developed as a treatment option for patients with localized prostate cancer.

Intraoperative high dose rate brachytherapy during breast-conserving surgery: A Prospective Pilot Study

PURPOSE

To evaluate feasibility, quality of life, toxicity, and cosmetic outcome for intraoperative breast cancer brachytherapy after breast-conserving surgery using high dose rate brachytherapy.

METHODS AND MATERIALS

Fifty-two consecutive women, ⩾50 years old, diagnosed with a unifocal non-lobular breast cancer ⩽3 cm, N0, underwent breast-conserving surgery and sentinel node biopsy. Twenty-five women received intraoperative brachytherapy pre-pathology at primary surgery and the others post-pathology, during a second procedure. An applicator, connected to a high dose rate afterloader, was used. Two of the women were excluded due to metastases found per-operatively at a frozen section from the sentinel node. Quality of life was evaluated using two validated health questionnaires. Treatment toxicity was documented according to the LENT-SOMA scale by two oncologists. The cosmetic result was evaluated using the validated freely available software BCCT.core 2.0.

RESULTS

The clinical procedure worked out well logistically. Seven women received supplementary external radiotherapy due to insufficient margins and, in one case, poor adaptation of the breast parenchyma to the applicator. No serious adverse effects from irradiation were registered. The results from the health questionnaires showed no major differences compared with reference groups from the Swedish population. Only two women were registered as having a "poor" cosmetic result while a majority of the women had a "good" outcome.

CONCLUSION

This pilot study shows that intraoperative brachytherapy is a feasible procedure and encourages further trials evaluating its role in treatment of early breast cancer.

Association between acute histopathological changes of rectal walls and late radiation proctitis following radiotherapy for prostate cancer

PURPOSE

The impact of acute histopathological changes (HC) of the rectum on development of late clinical proctitis (LCP) after external radiotherapy (RT) for prostate cancer is poorly explored and was the primary end point of this prospective study.

METHODS

In 70 patients, 15 HC of early rectal biopsies after RT were identified, whereby RT was conventional 2D RT in 41 cases and conformational 3D RT in 29. Associations of HC in anterior and posterior rectal walls (ARW, PRW) with LCP, acute endoscopic (AEP) and acute clinical proctitis (ACP) were statistically evaluated considering as explicative variables the patient general characteristics and the HC.

RESULTS

The mean patients' follow-up was 123.5 months (24-209). The median prostatic dose was 72 Gy (2 Gy/fraction). For the 41 and 29 patients the ARW and PRW doses were 64 and 49 Gy vs. 63 and 50 Gy, respectively. The incidence of LCP ≥ grade 2 at 10 years was 12.9%. The univariate (p = 0.02) and Kaplan-Meyer methods (p = 0.007) showed that the gland (or crypts) loss in the ARW was significantly associated with LCP. AEP and ACP occurred in 14.3 and 55.7% of cases. At multivariate level AEP significantly correlated with hemorrhoids (p = 0.014) and neutrophilia in ARW (p = 0.042).

CONCLUSIONS

Early after RT, substantial gland loss in ARW is predictive of LCP. To reduce this complication with conventional fractionation, we suggest keeping the mean dose to ARW ≤48-52 Gy.

Prostate high dose-rate brachytherapy as monotherapy for low and intermediate risk prostate cancer: Efficacy results from a randomized phase II clinical trial of one fraction of 19 Gy or two fractions of 13.5 Gy

BACKGROUND AND PURPOSE

High dose-rate (HDR) brachytherapy as monotherapy is a treatment option for localized prostate cancer, but optimal dose and fractionation is unknown. We report efficacy results of a randomized phase II trial of HDR monotherapy delivered as either one or two fractions.

MATERIALS AND METHODS

Eligible patients had low or intermediate risk prostate cancer, prostate volume <60 cc, and no androgen deprivation use. 170 patients were randomized to receive HDR as either a single fraction of 19 Gy or as two fractions of 13.5 Gy one week apart. Median age was 65 years, median PSA was 6.33 ng/ml, and Grade Group 1, 2 and 3 was present in 28%, 60%, and 12%, respectively. There was no difference in baseline factors between arms and 19%, 51% and 30% had low risk, favourable intermediate and unfavourable intermediate risk disease, respectively. The Phoenix definition was used to define biochemical failure, all local failures were confirmed by biopsy and toxicity was assessed using CTCAE v.4.

RESULTS

Median follow-up was 60 months. PSA decreased more quickly in the 2-fraction arm (p = 0.009). Median PSA at 5-years was 0.65 ng/ml in the single fraction and 0.16 ng/ml in the 2-fraction arm. The 5-year biochemical disease-free survival and cumulative incidence of local failure was 73.5% and 29% in the single fraction arm and 95% (p = 0.001) and 3% (p < 0.001) in the 2-fraction arm, respectively. Recurrence was not associated with initial stage, grade group, or risk group. Grade 2 late rectal toxicity occurred in 1% while the incidence of grade 2 and 3 urinary toxicity was 45% and 1%, respectively, with no difference between arms.

CONCLUSIONS

HDR monotherapy delivered as two fraction of 13.5 Gy is well tolerated with a high cancer control rate at 5 years. Single fraction monotherapy is inferior and should not be used.

A Brief Review of Low-Dose Rate (LDR) and High-Dose Rate (HDR) Brachytherapy Boost for High-Risk Prostate

For patients with unfavorable or high-risk prostate cancer, dose escalated radiation therapy leads to improved progression free survival but attempts to deliver increased dose by external beam radiation therapy (EBRT) alone can be limited by late toxicities to nearby genitourinary and gastrointestinal organs at risk. Brachytherapy is a method to deliver dose escalation in conjunction with EBRT with a potentially improved late toxicity profile and improved prostate cancer related outcomes. At least three randomized controlled trials have demonstrated improved biochemical control with the addition of either low-dose rate (LDR) or high-dose rate (HDR) brachytherapy to EBRT, although only ASCENDE-RT compared brachytherapy to dose-escalated EBRT but did report an over 50% improvement in biochemical failure with a LDR boost. Multiple single institution and comparative research series also support the use of a brachytherapy boost in the DE-EBRT era and demonstrate excellent prostate cancer specific outcomes. Despite improved oncologic outcomes with a brachytherapy boost in the high-risk setting, the utilization of both LDR, and HDR brachytherapy use is declining. The acute genitourinary toxicities when brachytherapy boost is combined with EBRT, particularly a LDR boost, are of concern in comparison to EBRT alone. HDR brachytherapy boost has many physical properties inherent to its rapid delivery of a large dose which may reduce acute toxicities and also appeal to the radiobiology of prostate cancer. We herein review the evidence for use of either LDR or HDR brachytherapy boost for high-risk prostate cancer and summarize comparisons between the two treatment modalities.

[Toxicity of multimodal regimens in prostate cancer]

Multimodal regimens consist en more than one treatment to treat localized prostate cancer. They are now proposed routinely for high-risk diseases. Different approaches could be defined: In conclusion, multimodal regimens increase the risk of side effects compared to surgery or radiotherapy alone. Indications of these approaches muste be discussed with the patients after a careful evaluation of the benefit/risk ratio.

Individualized Dose-Escalation of HDR Prostate Brachytherapy Implant to Decrease Required External Beam Radiation Dose: A Retrospective Feasibility Study

Purpose

High-dose-rate brachytherapy (HDR-BT) is commonly combined with external beam radiation therapy (EBRT) for the treatment of localized prostate cancer. Escalating the HDR-BT dose as far as organ-at-risk (OAR) constraints allow, on a personalized basis, would allow for a reduction in EBRT dose while achieving similar total biologic equivalence. The primary objective of this study was to determine the dosimetric feasibility of escalating the HDR-BT dose from 15 Gy to 16 or 17 Gy while continuing to meet OAR constraints from the original 15 Gy plan on an individualized basis.

Methods and materials

A total of 53 consecutive HDR-BT plans were retrospectively assessed to determine what percentage of plans could be reoptimized to deliver a dose of 16 Gy or 17 Gy, while meeting defined 15-Gy OAR constraints. Factors independently associated with dose escalation were examined.

Results

Thirty-nine plans (74%) and 2 plans (4%) were successfully escalated to a dose of 16 Gy and 17 Gy, respectively. Rectum V80 and urethra D_max were independently predictive of the ability to dose escalate to 16 Gy.

Conclusions

Individualized HDR-BT dose escalation beyond 15 Gy without compromising OAR constraints is dosimetrically feasible. This approach could allow for a corresponding reduction of EBRT fractions (ie, from 15 to 12 fractions) and would be beneficial in terms of resource savings for departments, convenience for patients, and potentially better tolerance of treatment with the expected reduction in biologically equivalent doses to OARs. A clinical trial is being developed to investigate the efficacy and tolerance of personalized HDR-BT/EBRT dose fractionation for localized intracapsular prostate cancer.

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.

SpaceOAR to improve dosimetric outcomes for monotherapy high-dose-rate prostate implantation in a patient with ulcerative colitis

High-dose-rate (HDR) brachytherapy is an attractive option for patients receiving definitive radiation therapy for prostate cancer with decreased overall dose to the pelvis. However, ulcerative colitis increases rectal toxicity risk and may be a contraindication. A synthetic hydrogel, SpaceOAR (Augmentix Inc., Waltham, MA, USA), can facilitate the use of HDR brachytherapy for patients where rectal toxicity is a limiting factor. SpaceOAR gel (13.19 cc) was utilized in a monotherapy HDR prostate treatment with Ir-192 under transrectal ultrasound guidance, with the intention of decreasing rectal dose. SpaceOAR gel was inserted transperineally into the patient 18 days prior to the procedure. The HDR brachytherapy procedure was tolerated without incident. All planning constraints were met, and the following dosimetry was achieved: Prostate - V_100% = 97.3%, V_150% = 35%, V_200% = 14.5%; Urethra - V_118% = 0%; Rectum - D_{2 cc} = 51.6%, V_75% = 0 cc. The rectum-catheter spacing was on average between 6-8 mm. Average spacing for our 10 most recent patients without SpaceOAR was 3 mm. SpaceOAR did not hinder or distort ultrasound imaging or increase treatment time. SpaceOAR successfully increases catheter-rectal wall spacing and decreases rectal dose due to improved planning capabilities, while decreasing the likelihood of rectal perforation. One application of this tool is presented to mitigate potential toxicities associated with ulcerative colitis. At five months, one week, and one day follow-up, the patient reported no bowel issues following HDR brachytherapy.