High Dose Rate Brachytherapy Treatment Research Articles

Assessment of integrated electromagnetic tracking for dwell position monitoring in a clinical HDR brachytherapy setting for prostate cancer

BackgroundElectromagnetic Tracking (EMT) technology has been integrated in a prototype high-dose-rate brachytherapy (HDR-BT) afterloading device. Its potential for dwell position (DP) monitoring has earlier been demonstrated in prostate phantoms. However, its performance for prostate BT in the clinical setting remains to be assessed. AimAssess the reliability and value of EMT measurements in transrectal ultrasound-based (TRUS-based) and computed tomography-based (CT-based) prostate HDR-BT. MethodsEMT measurements were conducted on 20 patients undergoing dual-fraction prostate HDR-BT monotherapy. In each treatment fraction an individual TRUS-based or CT-based treatment plan was generated. The measurements were compared to DPs of manually reconstructed needles in those TRUS-based or CT-based treatment plans. An internal reference sensor was also placed in one needle to assess internal movement levels and its potential for movement correction. ResultsFor TRUS-based treatments, median Euclidean distances (ED) of 1.00 mm were observed between EMT measurements and manual DP determination. Reference sensor movement was minimal at a median of 0.18 mm. For DPs measured in the CT-room and treatment room, median EDs of 1.60 mm and 2.24 mm compared to CT-based DP determination respectively were observed, indicating the system’s ability to detect changes in implant geometry over time and after patient repositioning. Median reference sensor movement of 0.97 mm was observed. Implementing reference sensor-based movement correction led to a significant but small decrease in ED for CT-based treatments. ConclusionEMT is suitable for TRUS-based prostate HDR-BT quality assurance and error detection. While EMT can identify changes in implant geometry in CT-based prostate HDR-BT treatments, it showed lower accuracy in this setting.

Preclinical prototype validation and characterization of a thermobrachytherapy system for interstitial hyperthermia and high-dose-rate brachytherapy

Background and purposeIntegrating simultaneous interstitial hyperthermia in high-dose-rate brachytherapy treatments (HDR-BT) is expected to lead to enhanced therapeutic effect. However, there is currently no device available for such an integration. In this study, we presented and validated the thermobrachytherapy (TBT) preclinical prototype system that is able to seamlessly integrate into the HDR-BT workflow. Materials and methodsThe TBT system consisted of an advanced radiofrequency power delivery and control system, dual-function interstitial applicators, and integrated connection and impedance matching system. The efficiency and minimum heating ability of the system was calculated performing calorimetric experiments. The effective-heating-length and heating pattern was evaluated using single-applicator split phantom experiments. The heating independence between applicators, the ability of the system to adaptable and predictable temperature steering was evaluated using multi-applicator split phantom experiments. ResultsThe system satisfied interstitial hyperthermia requirements. It demonstrated 50 % efficiency and ability to reach 6 °C temperature increase in 6 min. Effective-heating-length of the applicator was 43.7 mm, following the initial design. Heating pattern interference between applicators was lower than recommended. The system showed its ability to generate diverse heating patterns by adjusting the phase and amplitude settings of each electrode, aligning well with simulations (minimum agreement of 88 %). ConclusionsThe TBT preclinical prototype system complied with IHT requirements, and agreed well with design criteria and simulations, hence performing as expected. The preclinical prototype TBT system can now be scaled to an in-vivo validation prototype, including an adaptable impedance matching solution, appropriate number of channels, and ensuring biocompatibility and regulatory compliance.

Feasibility of a Tungsten-181 HDR brachytherapy source: Analysis of isotope production and source dosimetry

BackgroundInterest in Intensity Modulated Brachytherapy (IMBT) for High Dose Rate Brachytherapy (HDR) treatments has steadily increased in recent years. However, intensity modulation is not best optimized for currently used HDR sources since they emit high energy photons. To that end, the focus on IMBT has moved to middle energy sources, such as Ytterbium-169; yet even Yb-169 emits some high energy photons at a low yield. We present an alternative isotope, Tungsten-181 (T1/2 = 121 days) that is interesting due to its complete lack of high energy photon emissions. (Eavg = 58.9 keV, Emed = 57.5 keV) making it potentially favorable as high dose rate brachytherapy source from both a medical physics and health physics perspective. PurposeThe purpose of this study was to determine the feasibility of using W-181 as an HDR brachytherapy source; in this study we focused on W-181's production, dosimetric properties, and intensity modulation capabilities. MethodsWe determined the isotope production kinetics, its Dose Rate Constant, Radial Dose Function, photon self-absorption, and the shielding intensity modulation capabilities for a W-181 pellet source geometry using the MCNP6.2 Computer Simulations Code. All simulations were performed using a personal computer running an AMD Ryzen 5 3600 6-Core Processor 3.59 GHz. The number of histories run for each study were selected to produce relative simulation convergence errors in the MCNP tally output of less than 2%.Dosimetric calculations were made using the MCNP6.2 computer simulations code and activation analyses were determined mathematically using a Catenary kinetics analysis (also known as a Bateman Analysis) of W-181 and Tantlum-182 production from the neutron activation of a pure Tungsten-180 stable target. Since W-181 emits middle energy photons and has a high density, we also assessed the effects of photon self-absorption within a tungsten pellet. ResultsFrom our analysis, we determined that a 3.5 mm long and 0.6 mm in diameter is feasible for clinical applications. Our activation analyses found that these pellets can achieve W-181 activities up to 7.9Ci and 13Ci using neutron fluence rates of 4E14 cm−2 s−1 and 1E15 cm−2 s−1 respectively, which then would provide a dose rate of 1.84 ± 0.01 cG y/Ci/min at a depth of 1 cm from the source. Using our resulting Monte Carlo simulated Dose Rate Constant of 1.24 ± 0.02 cGy h−1∙U−1, a W-181 source in this geometry would require a source activity upwards of 10Ci for use in HDR treatments. In the intensity modulation analysis, only 0.1 mm of gold shielding was found to reduce a pellet's absorbed dose by over 50% while 0.3 mm of gold shielding, which is thin enough to theoretically fit between an HDR pellet and the inner catheter wall, was found to reduce the pellet's absorbed dose by over 85%. ConclusionsWhile W-181 has a lower specific activity than Ir-192 and Yb-169, it shows great promise as an isotope for use in Intensity Modulated Brachytherapy due to its easily shielded photons. We therefore expect that W-181 may lend itself best for use as a multi-pellet configuration in IMBT.

Practical experience with initial quality assurance of a high dose rate brachytherapy grid-based Boltzmann solver algorithm.

The purpose of this study was to validate the use of a model-based dose calculation algorithm (MBDCA), Acuros BV, for high dose rate brachytherapy treatment planning for a community-based hospital with a Bravos afterloader. Based on published AAPM recommendations, this work details a practical approach for community-based clinics to complete initial validation of Acuros BV, in order to add a MBDCA to a TG-43 based brachytherapy treatment planning program. Source dimensions and materials used in Acuros BV and TG-43 source models were compared to the physical source. TG-186 testing was completed with standardized test cases externally calculated with Monte Carlo compared to locally calculated with Acuros BV. Point doses calculated using TG-43 were compared to those calculated with Acuros BV in water at various dose grid settings. Secondary dose check software was used to evaluate dose distributions resembling clinical patient plans, both in water and on CT datasets representative of patient anatomy. The major source of discrepancy of source models was the length of modeled steel cable. TG-186 testing showed that the largest differences between Monte Carlo and Acuros BV dose distributions were located along the source axis for cases calculated in water, as well as located in regions of high dose gradients and within the applicator for the case calculated with a generic shielded applicator. An audit of point doses calculated with both TG-43 and Acuros BV in water found that dose grid settings significantly affected agreement. Secondary dose check software indicated that Acuros BV functioned satisfactorily, and a 5% threshold was adopted for secondary dose checks on gynecologic plans. This validation process indicated that Acuros BV met expected standards and affirmed its suitability for integration into this clinical practice's brachytherapy treatment planning.

Effective Differences between 2D and 3D Planned Brachytherapy in Lung Cancer: An Institutional Retrospective Study.

Background and Objectives: Advanced lung cancer is usually manifested by endoluminal tumor propagation, resulting in central airway obstruction. The objective of this study is to compare the high dose rate brachytherapy treatment outcomes in non-small-cell lung cancer (NSCLC) depending on the treatment planning pattern-two-dimension (2D) or three-dimension (3D) treatment planning. Materials and Methods: The study was retrospective and two groups of patients were compared in it (a group of 101 patients who underwent 2D planned high-dose-rate endobronchial brachytherapy (HDR-EBBT) in 2017/18 and a group of 83 patients who underwent 3D planned HDR-EBBT between January 2021 and June 2023). Results: In the group of 3D planned brachytherapy patients, there was a significant improvement in terms of loss of symptoms of bronchial obstruction (p = 0.038), but no improvement in terms of ECOG PS (European Cooperative Oncology Group Performance Status) of the patient (p = 0.847) and loss of lung atelectasis (if there was any at the beginning of the disease) (p = 0.781). Two-year overall survival and time-to-progression periods were similar for both groups of patients (p = 0.110 and 0.154). Fewer treatment complications were observed, and 91.4% were in 3D planned brachytherapy (BT) patients. Conclusions: Three-dimensionally planned HDR-EBBT is a suggestive, effective palliative method for the disobstruction of large airways caused by endobronchial lung tumor growth. Independent or more often combined with other types of specific oncological treatment, it certainly leads to the loss of symptoms caused by bronchial obstruction and the improvement of the quality of life of patients with advanced NSCLC. Complications of the procedure with 3D planning are less compared to 2D planned HDR-EBBT.

Salvage high-dose rate brachytherapy for local recurrence of prostate cancer after radical prostatectomy

Background. The current need for optimization of salvage treatment methods is dictated by the growing expansion of indications for radical prostatectomy in many centers in the developed countries of the world.Aim. To evaluate the effectiveness, toxicity, and technical characteristics of high-dose rate brachytherapy in treatment of local prostate cancer (PCa) recurrences after radical prostatectomy.Materials and methods. Between January 2015 and December 2020, salvage high-dose rate brachytherapy was performed in 17 patients at the Russian Scientific Center of Roentgenology and Radiology for local recurrence of PCa after radical prostatectomy. All patients underwent multiparametric magnetic resonance imaging of the pelvis at the stage of primary diagnosis in order to determine macroscopic tissue component in the prostate bed area. To rule out regional and distant metastases, all patients underwent positron emission tomography with 18F- or 68Ga-labeled prostate-specific membrane antigen. All patients included in the study underwent perineal biopsy of the prostate bed and seminal vesicles.Results. Median follow-up in the treatment group was 35.7 (24–54) months. Overall survival was 100 %. Prostatespecific antigen-specific survival was 88.2 %. There were no local recurrences of PCa in the treatment group. In patients with local PCa recurrence, significant predictors of treatment failure were the presence of clinically extremely high risk of progression at initial diagnosis (p = 0.003), development of biochemical relapse up to 24 months after main treatment (p = 0.001), and increased blood level of prostate-specific antigen above 10 ng/mL during registration of biochemical relapse (p = 0.002).Conclusion. High-dose rate brachytherapy is a safe and effective salvage treatment for local recurrence of PCa after radical prostatectomy. In addition to the brachytherapy technique, the diagnostic stage is also of great importance providing visualization of the exact location of tumor recurrence.

Clinical use of high dose-rate brachytherapy in treatment of patients with localized prostate cancer and infravesical obstruction

Background. High dose-rate brachytherapy is a new method of interstitial radiation therapy for treatment of localized prostate cancer. The difference from low dose therapy is temporary implantation of radiation sources with targeted high dose-rate irradiation of the affected organ.Aim. To evaluate 3-year effectiveness and safety of high dose-rate brachytherapy in patients with infravesical obstruction. Materials and methods. Between January of 2017 and December of 2019 at the Central Clinical Hospital “RZD-medicine”, 49 patients (mean age 67.8 ± 7.5 years) with verified prostate cancer diagnosis underwent high dose-rate brachytherapy in the regimen of 2 sessions of 15 Gy with 192Ir source. The inclusion criteria were disease stage ≤сТ2с, Gleason score ≤7. Patients were divided into 2 groups: 1st – patients with incidental prostate cancer (n = 21) who previously (more than 6 months ago, mean time 9.4 ± 2.4 months) underwent transurethral prostatectomy; 2nd – patients with verified prostate cancer (mean prostate volume 56 cm3) and obstructive symptoms without previous transurethral prostatectomy (n = 28).Results. In both groups, no intraoperative complications were observed. In 6 (28 %) patients of the 1st group and 2 patients of the 2nd group, grade II genitourinary toxicity in the form of moderate dysuria and nocturia was observed. Acute gastrointestinal toxicity was observed in 3 (14 %) patients of the 1st group, in the 2nd group such complications were absent. In the 2nd group during the postoperative period after the 2nd session, 4 patients (14 %) experienced acute urinary retention requiring cystostomy.Conclusion. High dose-rate brachytherapy is a safe and effective radical treatment method for patients with localized prostate cancer with obstructive symptoms who have contraindications for surgical treatment.

Clinical Outcomes of Sidewall/Parametrial Simultaneous Integrated Boost for Patients with Cervical Cancer

In the treatment of cervical cancer, simultaneous integrated boost (SIB) is a common technique to deliver increased dose to gross disease in the para-aortic and pelvic nodal basins. However, SIB to the pelvic sidewall/parametria is not well characterized in the literature. We hypothesized that sidewall simultaneous integrated boost (SIB) in the treatment of cervical cancer is associated with acceptable levels of toxicity. From 1/2009-12/2018, patients who received concurrent chemoradiation with external beam radiation therapy, utilizing a sidewall SIB technique, followed by low dose rate or high dose rate brachytherapy treatment were retrospectively identified. Sidewall SIB was defined as treatment at 2.1-2.4Gy/fraction to the parametria-usually performed for those with disease width >4cm at time of treatment start. Acute and late toxicity grading was defined by the Common Terminology Criteria for Adverse Events Version 5.0. Overall survival (OS), local control, progression-free survival (PFS), and toxicity were analyzed utilizing the Kaplan Meier method. Potential associations between cumulative D2cc for bladder and rectum and time to toxicity were investigated using Cox regression. Fifty-six patients with IB2-IVB cervical cancer treated with sidewall SIB were identified, with a median follow up of 7.0 years (95% CI: 6.3, 8.3). Patients had a median age of 43 years (range: 26-68); 2 (3.6%) had FIGO stage I, 7 (12.5%) stage II, 46 (82.1%) stage III, and 1 (1.8%) stage IV disease. A majority had squamous cell histology (83.9%). Nearly all patients (96.4%) received concurrent cisplatin chemotherapy. Rates of acute grade ≥3 gastrointestinal (GI), genitourinary (GU), vaginal, and hematologic toxicity were 1.8%, 1.8%, 0%, and 15.9% respectively. Rates of late grade ≥3 GI, GU, and vaginal toxicity were 11.3%, 18.5%, and 11.1% respectively. OS and local control rates at five years were 0.61 (95% CI: 0.46, 0.73) and 0.95 (95% CI: 0.84, 0.98), respectively. Median PFS was 7.8 years (95% CI: 2.4, Not reached). Cumulative D2cc bladder was not significantly associated with time to Grade 2 or greater (HR 1.04, p = 0.33) or Grade 3 or greater (HR 1.02; p = 0.64) GU toxicity. Cumulative D2cc rectum was not significantly associated with time to Grade 2 or greater (HR 1.06, p = 0.06) or Grade 3 or greater (HR 1.08; p = 0.09) GI toxicity. Sidewall SIB is a feasible technique for dose escalation in the treatment of cervical cancer with rates of acute and late toxicity consistent with other reports.

Pain in High-Dose-Rate Brachytherapy for Cervical Cancer: A Retrospective Cohort Study.

High-dose-rate brachytherapy (HDR) is part of the main treatment for locally advanced uterine cervical cancer. Our aim was to evaluate the incidence and intensity of pain and patients' satisfaction during HDR. Risk factors for suffering pain were also analyzed. A retrospective study was carried out by extracting data from patients who had received HDR treatment for five years. Postoperative analgesia had been administered using pre-established analgesic protocols for 48 h. Pain assessment was collected according to a protocol by the acute pain unit. Analgesic assessment was compared according to analgesic protocol administered, number of needles implanted, and type of anesthesia performed during the procedure. From 172 patients treated, data from 247 treatments were analyzed. Pain was considered moderate in 18.2% of the patients, and 43.3% of the patients required at least one analgesic rescue. Patients receiving major opioids reported worse pain control. No differences were found regarding the analgesic management according to the intraprocedural anesthesia used or the patients' characteristics. The number of inserted needles did not influence the postoperative analgesic assessment. Continuous intravenous infusion of tramadol and metamizole made peri-procedural pain during HDR mild in most cases. Many patients still suffered from moderate pain.

Dosimetric and workflow impact of synthetic-MRI use in prostate high-dose-rate brachytherapy

Target and organ delineation during prostate high-dose-rate (HDR) brachytherapy treatment planning can be improved by acquiring both a postimplant CT and MRI. However, this leads to a longer treatment delivery workflow and may introduce uncertainties due to anatomical motion between scans. We investigated the dosimetric and workflow impact of MRI synthesized from CT for prostate HDR brachytherapy. Seventy-eight CT and T2-weighted MRI datasets from patients treated with prostate HDR brachytherapy at our institution were retrospectively collected to train and validate our deep-learning-based image-synthesis method. Synthetic MRI was assessed against real MRI using the dice similarity coefficient (DSC) between prostate contours drawn using both image sets. The DSC between the same observer's synthetic and real MRI prostate contours was compared with the DSC between two different observers' real MRI prostate contours. New treatment plans were generated targeting the synthetic MRI-defined prostate and compared with the clinically delivered plans using target coverage and dose to critical organs. Variability between the same observer's prostate contours from synthetic and real MRI was not significantly different from the variability between different observer's prostate contours on real MRI. Synthetic MRI-planned target coverage was not significantly different from that of the clinically delivered plans. There were no increases above organ institutional dose constraints in the synthetic MRI plans. We developed and validated a method for synthesizing MRI from CT for prostate HDR brachytherapy treatment planning. Synthetic MRI use may lead to a workflow advantage and removal of CT-to-MRI registration uncertainty without loss of information needed for target delineation and treatment planning.

AAPM BTSC Report 377: Physicist Brachytherapy Training in 2021-A survey of therapeutic medical physics residency program directors.

Brachytherapy (BT) was the first radiotherapeutic technique used to treat human disease and remains an essential modality in radiation oncology. A decline in the utilization of BT as a treatment modality has been observed and reported, which may impact training opportunities for medical physics residents. A survey of therapeutic medical physics residency program directors was performed as part of an assessment of the current state of BT training during residency. In March 2021, a survey consisting of 23 questions was designed by a working unit of the Brachytherapy Subcommittee of the American Association of Physicists in Medicine (AAPM) and approved for distribution by the Executive Committee of the AAPM. The survey was distributed to the directors of the Commission on Accreditation of Medical Physics Education Programs (CAMPEP)-accredited therapeutic medical physics residency programs by the AAPM. The participant response was recorded anonymously in an online platform and then analyzed using MATLAB and Microsoft Excel software. The survey was distributed to the program directors of 110 residency programs. Over the course of 6 weeks, 72 directors accessed the survey online, and 55 fully completed the survey. Individual responses from the directors (including partial submissions) were evaluated and analyzed. Nearly all participating programs (98%) utilize high dose rate BT treatments with 74% using low dose rate BT techniques. All programs treated gynecological sites using BT, and the next most common treatment sites were prostate (80%) and breast (53%). Overall, the residency program directors had a positive outlook toward BT as a radiotherapeutic treatment modality. Caseload and time limitations were identified as primary barriers to BT training by some programs. Based on the responses of the program directors, it was identified that the residency programs might benefit from additional resources such as virtual BT training, interinstitutional collaborations as well as resident fellowships. Programs might also benefit from additional guidance related to BT-specific training requirements to help program directors attest Authorized Medical Physicist eligibility for graduating residents.

ORIGIN, an EU project targeting real-time 3D dose imaging and source localization in brachytherapy: Commissioning and first results of a 16-sensor prototype

The ORIGIN project targets the production and qualification of a real-time radiation dose imaging and source localization system for both Low Dose Rate (LDR) and High Dose Rate (HDR) brachytherapy treatments, namely radiotherapy based on the use of radioactive sources implanted in the patient’s body. This goal will be achieved through a 16-fiber sensor system, engineered to house in a clear-fiber tip a small volume of the scintillator to allow point-like measurements of the delivered dose. Each fiber is optically coupled to a sensor with single photon sensitivity (Silicon Photomultipliers — SiPMs) operating in counting mode. The readout is based on the CITIROC1A ASIC by WEEROC, embedded in the FERS-DT5202 scalable platform designed by CAEN S.p.A. Linearity and sensitivity together with the fiber response uniformity, system stability, and measurement reproducibility are key features for a instrument aiming to perform dose measurements. Characterization was carried out in the laboratory, using an X-ray cabinet; preliminary dose rate measurements were performed in clinical conditions.

GSOR3 Presentation Time: 9:10 AM: Adding Free Needles and Optimization to Tandem and Ovoids in High Dose Rate Brachytherapy Treatment for Cervical Cancer: How Much Do They Matter?

<h3>Purpose</h3> With increased MRI utilization, targets for cervical cancer are more customized. This in turn makes hybrid applicators more essential, creating treatment plans which deviate significantly from classical pear-shaped dose distributions. This study analyzes the dosimetric impact of integrating free needles into tandem and ovoid (T&O) HDR-brachytherapy treatment for locally advanced cervical cancer. <h3>Materials and Methods</h3> 29 patients with cervical cancers (FIGO stage IB-IIIC2) were treated with 125 fractions. HR_CTV and OARs (bladder, rectum, sigmoid) were contoured by one physician. All delivered plans were optimized using a previously described ‘two-step' optimization procedure, with the goal of maximizing D90(HR-CTV), minimizing dose to OARs, while maintaining the pear aspect of the Prescription Dose iso-surface. These plans were then compared to two additional plans, created using only T&O, re-optimized to either match the original plans for coverage (D90 to HR-CTV) or for OAR sparing (D2cc). Dosimetric information was extracted from TPS and distributions evaluated using histograms and statistical t-test. <h3>Results</h3> The CTV_HR volume for this series was 53.58±23.46 cm3. The dose coverage of the target for the clinical plans was excellent, at 99.14±6.62 %PD. There was a negative correlation between D90 and HR-CTV, in that larger volume of HR-CTV in HDR brachytherapy cervical cancer cases tends to have an outcome of lower dose coverage (shown in figure 1). When clinical plans, using T&O and free needles, were compared with T&O only plans optimized to match D90, the mean D2cc calculated from plans without needles was higher than those from original plans by an average of 29%, 22%, 27% for bladder, rectum and sigmoid, respectively. A t-test between the two populations, with a p-values < 0.00006 shows that they are significantly different. The highest difference of D2cc between original plans and re-optimized plans were 261%, 294%, and 193% for bladder, rectum, and sigmoid, respectively. When clinical plans were compared to re-optimized T&O only, matching OAR toxicity, the D90(HR-CTV) coverage of the plans without needles, was as expected, lower by an average of 21% for the entire series. The T-test between the two populations had a p-value < 2.2e-16. The maximum percentage difference of the dose coverage was 128% compared between re-optimized T&O only and original plans with matched toxicity. <h3>Conclusions</h3> Free handed needles are an easy to implement, inexpensive add-on to a classical T&O, in order to create a ‘hybrid' applicator. Based on this series of patients and the dosimetric data from their clinical plans, we believe that integrating free-handed needles and optimization methods into traditional T&O cervical cancer brachytherapy treatment is highly beneficial for controlling organs-at-risk toxicity while achieving optimal coverage for HR-CTV and preserving an overall ‘pear'-shape-like aspect of the overall dose distribution. Our findings suggest that the use of additional needles should be considered for cases with a larger or asymmetric volume of HR-CTV. This study, is to our knowledge, the first to quantify the dosimetric benefits of free-needles augmented T&O when compared to classical T&O. We recommend in addition to adding free needles the two step optimization method to best take advantage of the degrees of freedom one has by using hybrid applicators.

PO05: Single Fraction High-Dose-Rate Brachytherapy: A Scoping Review on Outcomes and Toxicities for All Disease Sites

<h3>Purpose</h3> There is increasing interest in single fraction treatments in radiation oncology to improve efficiency and lower costs. Brachytherapy is well positioned to safely deliver highly conformal single fraction doses of radiation. Low-dose-rate brachytherapy has the advantage of being delivered in a single treatment, but high-dose-rate brachytherapy (HDR) has more traditionally been delivered over multiple treatments. Expanding single fraction HDR treatments could be a significant area of growth. A scoping literature review was conducted to better understand the available literature on single fraction HDR for all disease sites. <h3>Materials and Methods</h3> The review was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines. The PubMed database was queried from 1994-2021 using the search terms: "brachytherapy", "high-dose-rate", and "single fraction". Included studies were limited to single fraction HDR. Studies that involved the same cohort, follow up less than 1 year, sample size <10 patients, review articles, and case reports were excluded, which resulted in 51 included studies. <h3>Results</h3> Liver had the highest number of studies with 18 (7 primary, 11 metastasis) and included reported outcomes on a total of 618 patients. Single fraction doses ranged from 10-25 Gy. Median follow-up ranged from 11-33 months. Local control rates ranged from 37-98%. Grade 3 or higher toxicities in the acute/late setting were reported in 3 patients in only 1 study.Prostate cancer had the second highest number of studies with 16 (14 definitive, 2 salvage) and included reported outcomes on a total of 1474 patients. Single fraction doses ranged from 19-21 Gy. Median follow-up ranged from 20-72 months. PSA control outcomes after definitive treatment ranged from 65-94% and salvage treatments from 5-84%. Grade 3 or higher toxicities in the acute/late setting ranged from 0-6%. Breast cancer had the third highest number of studies with 7 and included reported outcomes on a total of 268 patients. Single fraction doses ranged from 16-20 Gy. Median follow-up ranged from 24-72 months. Local control rates were 100%. Grade 3 or higher toxicities in the acute/late setting ranged from 0-6%. The remaining 10 studies included the following sites: 4 gastrointestinal, 2 lung, 2 head and neck, 1 glioma, and 1 endometrial. Conclusions from these studies are limited given the small number of patients treated within each respective disease site. <h3>Conclusions</h3> There is a medium sized body of literature using single fraction HDR. Currently used regimens appear safe but efficacy appears to vary by different disease sites. Outcomes are more promising for breast and liver while are less encouraging for prostate. Additional prospective evaluation of single fraction HDR regimens are warranted in disease sites outside of prostate cancer.

Prediction of disease progression indicators in prostate cancer patients receiving HDR-brachytherapy using Raman spectroscopy and semi-supervised learning: a pilot study

This work combines Raman spectroscopy (RS) with supervised learning methods—group and basis restricted non-negative matrix factorisation (GBR-NMF) and linear discriminant analysis (LDA)—to aid in the prediction of clinical indicators of disease progression in a cohort of 9 patients receiving high dose rate brachytherapy (HDR-BT) as the primary treatment for intermediate risk (D’Amico) prostate adenocarcinoma. The combination of Raman spectroscopy and GBR-NMF-sparseLDA modelling allowed for the prediction of the following clinical information; Gleason score, cancer of the prostate risk assessment (CAPRA) score of pre-treatment biopsies and a Ki67 score of < 3.5% or > 3.5% in post treatment biopsies. The three clinical indicators of disease progression investigated in this study were predicted using a single set of Raman spectral data acquired from each individual biopsy, obtained pre HDR-BT treatment. This work highlights the potential of RS, combined with supervised learning, as a tool for the prediction of multiple types of clinically relevant information to be acquired simultaneously using pre-treatment biopsies, therefore opening up the potential for avoiding the need for multiple immunohistochemistry (IHC) staining procedures (H&E, Ki67) and blood sample analysis (PSA) to aid in CAPRA scoring.

Raman spectroscopy and supervised learning as a potential tool to identify high-dose-rate-brachytherapy induced biochemical profiles of prostate cancer.

High-dose-rate-brachytherapy (HDR-BT) is an increasingly attractive alternative to external beam radiation-therapy for patients with intermediate risk prostate cancer. Despite this, no bio-marker based method currently exists to monitor treatment response, and the changes which take place at the biochemical level in hypo-fractionated HDR-BT remain poorly understood. The aim of this pilot study is to assess the capability of Raman spectroscopy (RS) combined with principal component analysis (PCA) and random-forest classification (RF) to identify radiation response profiles after a single dose of 13.5Gy in a cohort of nine patients. We here demonstrate, as a proof-of-concept, how RS-PCA-RF could be utilised as an effective tool in radiation response monitoring, specifically assessing the importance of low variance PCs in complex sample sets. As RS provides information on the biochemical composition of tissue samples, this technique could provide insight into the changes which take place on the biochemical level, as result of HDR-BT treatment.

Optimization of catheter's implementation in the mold, in the case of vaginal HDR brachytherapy treatment.

BackgroundThe purpose of this study was to evaluate and compare results obtained in high dose rate (HDR) brachytherapy treatment of vaginal cancer. Different catheters distributions inside the custom mold were explored. The difference between those distributions is the position of the posterior catheter located near the rectum in the actual custom mold applicator used in different hospitals, each one having a catheter displacement of 0.5 which is equal to the length of a step position. The best catheters distribution offering an optimal dose distribution: better coverage of the clinical target volume (CTV), while reducing the dose received by organs at risk (OARs), were discussed.Materials and methodsA group of 60 patients treated with HDR brachytherapy, alone or in combination with external radiotherapy, was investigated. A custom mold is normally used for HDR brachytherapy vaginal cancer treatment. Three different geometrical positions of the catheters (G1, G2 and G3) and, consequently, 3 different dosimetries were simulated out for each patient on the CT images, using the Oncentra planning system. The coverage of the CTV was studied.ResultsThe average volume treated was 30.46 cc (min = 9.8 cc, max = 70.86 cc). The total prescribed dose, including external and internal radiotherapy, was 80 Gy. We evaluated conformity index (CI), dose homogeneity index (DHI) and conformality index (COIN) indices for the three implantation geometries to reach the same coverage criteria of the CTV. The D2cc parameter allowed the evaluation of the dose received by the OARs. For the rectum, a dose reduction of 9.67% (range 0.29–32.86) was obtained with the second geometry of implantation compared to 10.14% (range 1.43–28.33) with the third geometry. For the bladder, the second geometry of implantation showed a better preservation for this organ [15.93% (range 0.86–58.71) vs. 8.35% (range 0.33–30.43) with the third geometry]. The sigmoid was more protected using the second plan of implantation as well [6.33% (range 0.14–40.71) for the second implantation compared to 5.95% (range 0.33–36) for the third implantation].ConclusionsG2 and G3 catheters’ distribution, having catheter position farther from the mold wall and so from the vaginal wall compared to the catheter position applied showed a better protection for the OARs while giving the same prescribed dose for the CTV.

The changing radiation oncology landscape in New Zealand.

This paper outlines the New Zealand (NZ) responses to the biennial facilities surveys of The Royal Australian and New Zealand College of Radiologists (RANZCR), Faculty of Radiation Oncology (FRO) from 2011 to 2019. The facilities survey is conducted by the FRO Economics and Workforce Committee (FROEWC) and focuses on equipment, treatment activities and staffing. The number of facilities increased by two to 10, both in the private sector. The total number of linear accelerators (linacs) increased by four; one in public and three in private. The majority of linacs were over 8 years old (62.5%). Treatment courses have increased by 19% and fraction numbers by 13.7%. Courses per linac have remained relatively constant. There was growth in IMRT, orthovoltage, high dose rate brachytherapy and paediatric treatments. There was a slow increase in number of radiation oncologists and trainees. The number of radiation therapists was unchanged with a 20% increase in treatment courses per radiation therapist. Physicist numbers have increased but 61.4% of physicists are overseas-trained and vacancies persist. The survey results indicate a rapidly changing radiation oncology landscape in NZ between 2011 and 2019. The challenges of increases in cancer numbers, treatment courses and complexity of treatments and a need to focus on quality standards against a set of minimal increase in machine numbers, ageing machines, static or slowly increasing staffing numbers and heavy reliance on overseas staffing require a national review of radiation oncology services to ensure a sustainable future.

Technical note: Commissioning of an ultrasound-compatible surrogate vaginal cylinder for transvaginal ultrasound-based gynecologic high-dose-rate brachytherapy.

To provide a comprehensive set of commissioning tests for clinical implementation of three-dimensional transvaginal ultrasound (3D TVUS) as a replacement of computed tomography (CT) for applicator reconstruction in gynecologic (GYN) intracavitary high-dose-rate brachytherapy (HDRBT) with a multi-channel vaginal cylinder (MCVC). We introduce an ultrasound-compatible "surrogate" vaginal cylinder (SVC) for reconstruction of Elekta's CT-MR Multi Channel Applicator (MCVC) in 3D TVUS. The MCVC is digitized over the SVC in 3DUS using digital library model overlay. Consulting guidelines from various sources (CPQR, GEC-ESTRO, AAPM), we identify and describe three tests specific to commissioning the SVC: (1) verification of SVC outer dimensions, (2) source position accuracy of MCVC digitization over the SVC in 3D TVUS, and (3) MRI/US registration error. The SVC outer dimensions (diameter and A-D marker locations) were well matched to the MCVC, however a 0.6mm discrepancy in length between cylinder tips was observed. Source position accuracy was within 1mm (tolerance recommended by CPQR) when reconstructing the MCVC in 3D TVUS. Dice similarity coefficients and target registration error for MRI/3D TVUS registration was similar to MRI/CT registration, which is the clinical standard. These commissioning tests are performed using institutional equipment but provide the framework for any practitioner to repeat in their own setup, to demonstrate safe adoption of the 3D TVUS system for patient treatments. We demonstrate that MRI/US-based workflow achieves similar source position accuracy and image registration error as standard MRI/CT, which is consistent with standard tolerances. This is a critical step toward replacement of CT with US in GYN HDRBT treatments with the MCVC.

The Experience of Pain and Anxiety in Cervical Cancer Patients Undergoing Multiple Fraction High-Dose Rate Brachytherapy: A Prospective Observational Study

Purpose: To evaluate the anxiety and pain levels of cervical cancer patients undergoing intracavitary multifraction high-dose rate (HDR) brachytherapy, as part of a process to develop guidelines for quality patient-centered care. Methods: Cervical cancer patients (n = 31) undergoingmultiple fraction HDR brachytherapy treatment at the National Institute of Oncology in Rabat (Morocco) completed ratings of pain and anxiety intensity using 11-point verbal analog scales, at 6 key time points over 2 brachytherapy insertion procedures and 4 brachytherapy fractions. Women were evaluated for psychological status at baseline before starting the brachytherapy process using the Hospital Anxiety and Depression Scale (HADS). Scores were grouped as follows: 0 - 7 = normal, 8 - 10 = borderline, 11 - 21 = abnormal. Factors that could affect anxiety levels such as education level, relationship status, number of pregnancies and prior surgical history were documented. Results: Between July and August 2020, 31 women with a median age of 49.6 years were evaluated (range: 27 - 70). The HADS score identified depression in 5 patients (16.1%) and anxiety in 12 patients (38.7%). Throughout both treatment procedures, anticipatory anxiety was reported, with a maximum intensity in the operating room during spinal anesthesia (3.23 ± 1.7) and during applicator insertion (2.97 ± 2.4). Moderate-to-severe anxiety scores were reported in 25.8% and 22.6% of patients respectively. Level of education showed a significant correlation with anxiety scores (p = 0.027). Pain increased significantly during the procedure (p ± 1.4) and applicator removal (4.74 ± 1.5) turned out to be the most painful parts of the procedure. No correlation was found between pain and anxiety levels. Conclusion: Intracavitary multifraction high-dose rate brachytherapy is associated with mild to moderate levels of pain and anxiety, although a subset of patients reported more severe symptoms and may require additional medical and psychological support, with particular emphasis on bed-rest duration and applicator removal. The development of effective interventions (both pharmacological and non-pharmacological) is needed to improve women’s experiences of brachytherapy for locally advanced cervical cancer.