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BACKGROUND: Ultra-high dose rate irradiation (≥40 Gy/s, FLASH) has been shown to reduce normal tissue toxicity, while maintaining tumor control compared to conventional dose-rate radiotherapy. The radiolytic oxygen (O2) depletion (ROD) resulting from FLASH has been proposed to explain the normal tissue protection effect; however, in vivo experiments have not confirmed that FLASH induced global tissue hypoxia. Nonetheless, the experiments reported are based on volume-averaged measurement, which have inherent limitations in detecting microscopic phenomena, including the potential preservation of stem cells niches due to local FLASH-induced O2 depletion. Computational modeling offers a complementary approach to understand the ROD caused by FLASH at the microscopic level. PURPOSE: We developed a comprehensive model to describe the spatial and temporal dynamics of O2 consumption and transport in response to irradiation in vivo. The change of oxygen enhancement ratio (OER) was used to quantify and investigate the FLASH effect as a function of physiological and radiation parameters at microscopic scale. METHODS: We considered time-dependent O2 supply and consumption in a 3D cylindrical geometry, incorporating blood flow linking the O2 concentration ([O2]) in the capillary to that within the tissue through the Hill equation, radial and axial diffusion of O2, metabolic and zero-order radiolytic O2 consumption, and a pulsed radiation structure. Time-evolved distributions of [O2] were obtained by numerically solving perfusion-diffusion equations. The model enables the computation of dynamic O2 distribution and the relative change of OER (δROD) under various physiological and radiation conditions in vivo. RESULTS: Initial [O2] level and the subsequent changes during irradiation determined δROD distribution, which strongly depends on physiological parameters, i.e., intercapillary spacing, ultimately determining the tissue area with enhanced radioresistance. We observed that the δROD/FLASH effect is affected by and sensitive to the interplay effect among physiological and radiation parameters. It renders that the FLASH effect can be tissue environment dependent. The saturation of FLASH normal tissue protection upon dose and dose rate was shown. Beyond ∼60 Gy/s, no significant decrease in radiosensitivity within tissue region was observed. In turn, for a given dose rate, the change of radiosensitivity became saturated after a certain dose level. Pulse structures with the same dose and instantaneous dose rate but with different delivery times were shown to have distinguishable δROD thus tissue sparing, suggesting the average dose rate could be a metric assessing the FLASH effect and demonstrating the capability of our model to support experimental findings. CONCLUSION: On a macroscopic scale, the modeling results align with the experimental findings in terms of dose and dose rate thresholds, and it also indicates that pulse structure can vary the FLASH effect. At the microscopic level, this model enables us to examine the spatially resolved FLASH effect based on physiological and irradiation parameters. Our model thus provides a complementary approach to experimental methods for understanding the underlying mechanism of FLASH radiotherapy. Our results show that physiological conditions can potentially determine the FLASH efficacy in tissue protection. The FLASH effect may be observed under optimal combination of physiological parameters, not limited to radiation conditions alone.

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BACKGROUND: Achieving a clinically acceptable dose distribution with commercial vaginal applicators for brachytherapy of recurrent parauterine tumors is challenging. However, the application of three-dimensional (3D) printing technology in brachytherapy has been widely acknowledged and can improve clinical treatment outcomes. PURPOSE: This study aimed to introduce an individual curved-needle interstitial template (ICIT) created using 3D printing technology for high-dose-rate (HDR) brachytherapy with interstitial treatment to provide a clinically feasible approach to distal parauterine and vaginal cuff tumors. The entire workflow, including the design, optimization, and application, is presented. METHODS: Ten patients with pelvic cancer recurrence were examined at our center. The vaginal topography was filled with gauze strips soaked in developer solution, and images were obtained using computed tomography (CT) and magnetic resonance imaging (MRI). Curved needle paths were designed, and ICITs were 3D-printed according to the high-risk clinical target volume (HRCTV) and vaginal filling model. The dose and volume histogram parameters of the HRCTV (V100, V200, D90, and D98) and organs at risk (OARs) (D2cc) were recorded. RESULTS: All patients completed interstitial brachytherapy treatment with the 3D-printed ICIT. One patient experienced vaginal cuff tumor recurrence, and nine patients experienced parametrial tumor recurrence (four on the left and five on the right). We used two to five interstitial needles, and the maximum angle of the curved needle was 40°. No source obstruction events occurred during treatment of these 10 patients. The doses delivered to the targets and OARs of all patients were within the dose limits and based on clinical experience at our center. CONCLUSION: The ICIT is a treatment option for patients with distal parauterine tumor recurrence. This method addresses the limitations of vaginal intracavitary and standard interstitial applicators. The ICIT has the advantages of biocompatibility, personalization, and magnetic resonance imaging compatibility.

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Treatments at ultra-high dose rate (UHDR) have the potential to improve the therapeutic index of radiation therapy (RT) by sparing normal tissues compared to conventional dose rate irradiations. Insufficient and inconsistent reporting in physics and dosimetry of preclinical and translational studies may have contributed to a reproducibility crisis of radiobiological data in the field. Consequently, the development of a common terminology, as well as common recording, reporting, dosimetry, and metrology standards is required. In the context of UHDR irradiations, the temporal dose delivery parameters are of importance, and under-reporting of these parameters is also a concern.This work proposes a standardization of terminology, recording, and reporting to enhance comparability of both preclinical and clinical UHDR studies and and to allow retrospective analyses to aid the understanding of the conditions which give rise to the FLASH effect.

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OBJECTIVES: Image-guided adaptive brachytherapy (IGABT) is the standard of care for patients with cervical cancer. The objective of this study was to compare the treatment outcomes and adverse effects of computed tomography (CT)-guided and magnetic resonance imaging (MRI)-guided scenarios. MATERIALS AND METHODS: Data of patients with cervical cancer treated using external beam radiotherapy followed by IGABT from 2012 to 2016 were retrospectively reviewed. CT-guided IGABT was compared with the three modes of MRI-guided IGABT: pre-brachytherapy (MRI Pre-BT) without applicator insertion for fusion, planning MRI with applicator in-place in at least 1 fraction (MRI ≥1Fx), and MRI in every fraction (MRI EveryFx). Patient characteristics, oncologic outcomes, and late radiation toxicity were analyzed using descriptive, survival, and correlation statistics. RESULTS: Overall, 354 patients were evaluated with a median follow-up of 60 months. The 5-year overall survival (OS) rates were 61.5%, 65.2%, 54.4%, and 63.7% with CT-guided, MRI PreBT, MRI ≥1Fx, and MRI EveryFx IGABT, respectively with no significant differences (p = 0.522). The 5-year local control (LC) rates were 92.1%, 87.8%, 80.7%, and 76.5% (p = 0.133), respectively, with a significant difference observed between the CT-guided and MRI ≥1Fx (p = 0.018). The grade 3-4 late gastrointestinal toxicity rates were 6% in the CT-guided, MRI ≥1Fx, and MRI EveryFx, and 8% in MRI PreBT. The grade 3-4 late genitourinary toxicity rates were 4% in the CT-guided, 2% in MRI PreBT, 1% in MRI ≥1Fx, and none in MRI EveryFx. No significant differences were observed in the oncologic and toxicity outcomes among MRI PreBT, MRI ≥1Fx, and MRI EveryFx. CONCLUSIONS: CT-guided IGABT yielded an acceptable 5-year OS, LC, and toxicity profile compared with all MRI scenarios and is a potentially feasible option in resource-limited settings.

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Purpose This study evaluates the therapeutic outcomes and practical application of high-dose-rate (HDR) brachytherapy in managing cervical and endometrial cancers at a tertiary hospital in the UAE, focusing on treatment efficacy, safety, and patient-reported outcomes. Methods A retrospective analysis was conducted on 368 female patients treated between January 2008 and January 2022. Data included demographic information, cancer type, histopathology, treatment details, and survival outcomes. Statistical analyses were performed using descriptive and inferential statistics. Results The cohort comprised 275 cervical cancer patients (74.73%) and 93 endometrial cancer patients (25.27%). The majority were non-nationals (79.62%). The mean age was 57 years. Squamous cell carcinoma was the most common histopathological type (63.59%). HDR brachytherapy was administered to 290 patients (79.89%). The 12-month survival probability was significantly higher in the HDR-Brachy group (75%, 95% CI: 60% to 85%) compared to the noHDR-Brachy group (50%, 95% CI: 35% to 65%), with a hazard ratio of 0.953 (p=0.0035). At the last review, 86.68% of patients were alive, and disease progression was observed in 37.88% of patients. Conclusion HDR brachytherapy significantly improves survival outcomes in cervical and endometrial cancer patients. Continued efforts to enhance access and standardize brachytherapy protocols are essential to optimize treatment efficacy and patient outcomes in similar healthcare settings.

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PURPOSE: Intraprostatic recurrence (IRR) of prostate cancer after radiation therapy is increasingly identified. Our objective was to review the literature to determine the optimal workup for identifying IRR, the management options, and practical considerations for the delivery of re-irradiation as salvage local therapy. METHODS: We performed a systematic review of available publications and ongoing studies on the topics of IRR, with a focus on salvage re-irradiation. RESULTS: Work up of biochemically recurrent prostate cancer includes PSMA PET/CT and multiparametric MRI, followed by biopsy to confirm IRR. Management options include continued surveillance, palliative hormonal therapy, and salvage local therapy. Salvage local therapy can be delivered using re-irradiation with low dose rate brachytherapy, high dose rate (HDR) brachytherapy, and stereotactic body radiotherapy (SBRT), as well as non-radiation modalities, such as cryotherapy, high-intensity focused ultrasound, irreversible electroporation and radical prostatectomy. Data demonstrate that HDR brachytherapy and SBRT have similar efficacy compared to the other salvage local therapy modalities, while having more favorable side effect profiles. Recommendations for radiation therapy planning and delivery using HDR and SBRT based on the available literature are discussed. CONCLUSION: Salvage re-irradiation is safe and effective and should be considered in patients with IRR.

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OBJECTIVE: There are numerous curative treatment possibilities for prostate cancer. In patients who have undergone rectal extirpation for rectal cancer treatment, curative options are limited due to anatomic changes and previous irradiation of the pelvis. In this analysis, we validate the feasibility of CT-guided transperineal interstitial brachytherapy for this specific scenario. PATIENTS AND METHODS: We analyzed the treatment procedures and outcomes of 5 patients with metachronic nonmetastatic prostate cancer. Ultrasound-guided brachytherapy was not possible in any of the patients. Of these 5 patients, 3 were treated for prostate cancer using temporary brachytherapy with Ir-192 only, and 2 were treated with external-beam radiation therapy and temporary brachytherapy as a boost. CT-guided brachytherapy was performed in all patients. We analyzed the feasibility, efficacy, treatment-related toxicity, and quality of life (EORTC-30, IEFF, IPSS, and ICIQ questionnaires) of the treatments. RESULTS: Median follow-up was 35 months. Two out of five patients received boost irradiation (HDR 2â€¯× 9 Gy, PDR 30 Gy). Three out of five patients were treated with PDR brachytherapy in two sessions up to a total dose of 60 Gy. Dosimetric parameters were documented as median values as follows: V100 94.7% (94.5-98.4%), D2bladder 64.3% (50.9-78.3%), D10urethra 131.05% (123.2%-141.2%), and D30urethra 122.45% (116.2%-129.5%). At the time of analysis, no biochemical recurrence had been documented. Furthermore, neither early nor late side effects exceeding CTCAE grade 2 were documented. CONCLUSION: CT-guided transperineal brachytherapy of the prostate in patients with previous rectal surgery and radiation therapy is safe and represents a possible curative treatment option. Brachytherapy can be considered for patients with metachronic prostate cancer in this specific scenario, albeit preferably in experienced high-volume centers.

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BACKGROUND AND PURPOSE: The upgrade of major equipment can be disruptive to clinical operations and introduce risk as policy and procedures need to adapt to new technical possibilities and constraints. We describe here the transition from GammaMedPlus-iX to Bravos in a busy brachytherapy clinic, involving four afterloaders across two sites. MATERIAL AND METHODS: Our clinic employs three high-dose-rate remote afterloaders in four dedicated treatment vaults at the main site and a fourth afterloader at a regional location. Of more than 600 new HDR treatment plans performed annually, most are planned and treated intraoperatively. Most treatments are for prostate cancer, followed by GYN, intraoperative brachytherapy, GI, and other sites. Applicators used include vendor-provided applicators as well as third party applicators and in-house 3D-printed devices to provide interstitial, intracavitary, intraluminal, and surface treatments. All applicators were commissioned according to recommended guidelines. The choice of tolerances and the design of new procedures were informed by current guidelines and leveraged new HDR afterloader functionalities. A review of clinical operations in the 4 months postupgrade was conducted to evaluate the feasibility of new tolerances and the effectiveness of new procedures. RESULTS: The procedures outlined improved and standardized afterloader QA and treatment protocols with clear actionable steps for staff to follow to ensure treatments are delivered as planned. Re-commissioning of applicators yielded results similar to those previously reported by other investigators. A review of initial treatment data revealed that in one case, due to the implementation of tight tolerances, obstruction near the tip of the channel was detected and corrected prior to treatment. It confirms that the implementation of the tolerances adopted is feasible and effective in flagging treatment deviations. CONCLUSION: Enhanced procedures and QA processes were implemented successfully. We established clear actionable steps to follow by staff to ensure that treatments are delivered accurately.

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Background. Peri-operative interventional radiotherapy (POIRT) entails tumor resection, catheter implantation in the same surgery, and irradiation within the peri-operative period. It allows for maximal tumor burden reduction, better tumor bed identification, more flexible implant geometry, highly conformal irradiation, and treatment delay minimization. We reviewed the published local control, survival, toxicity, and quality of life (QOL) outcomes with POIRT for head and neck cancers (HNCs) in primary and re-irradiation settings. Materials and Methods. A systematic search of PubMed, Scopus, Science Direct, and other databases, supplemented by bibliography scanning and hand-searching, yielded 107 titles. Fifteen unique articles were eligible, five of which were merged with more updated studies. Of the ten remaining studies, four reported on primary POIRT, and seven reported on reirradiation POIRT. Given data heterogeneity, only qualitative synthesis was performed. Results. Primary POIRT in early tongue cancer results in 6-year recurrence-free (RFS) and overall survival (OS) of 92% for both; in advanced HNCs, the 9-year RFS and OS rates are 52% and 55%. Grade 1-2 toxicity is very common; grade 3-4 toxicity is rare, but grade 5 toxicity has been reported. POIRT re-irradiation for recurrent HNCs results in 5y RFS and OS rates of 37-55% and 17-50%; better outcomes are achieved with gross total resection (GTR). QOL data are lacking. Conclusions. Primary POIRT is safe and effective in early tongue cancers; its use in other HNC sites, especially in advanced disease, requires careful consideration. Re-irradiation POIRT is most effective and safe when combined with GTR; toxicity is significant and may be limited by careful case selection, implant planning and execution, use of smaller fraction sizes, and adherence to homogeneity constraints. Study Registration Number. PROSPERO Registry Number CRD42024548294.

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PURPOSE: High dose-rate (HDR) brachytherapy is integral for the treatment of numerous cancers. Preclinical studies involving HDR brachytherapy are limited. We aimed to describe a novel platform allowing multi-modality studies with clinical HDR brachytherapy and external beam irradiators, establish baseline dosimetry standard of a preclinical orthovoltage irradiator, to determine accurate dosimetric methods. METHODS: A dosimetric assessment of a commercial preclinical irradiator was performed establishing the baseline dosimetry goals for clinical irradiators. A 3D printed platform was then constructed with 14 brachytherapy channels at 1cm spacing to accommodate a standard tissue culture plate at a source-to-cell distance (SCD) of 1 cm or 0.4 cm. 4-Gy CT-based treatment plans were created in clinical treatment planning software and delivered to 96-well tissue culture plates using an Ir192 source or a clinical linear accelerator. Standard calculation models for HDR brachytherapy and external beam were compared to corresponding deterministic model-based dose calculation algorithms (MBDCAs). Agreement between predicted and measured dose was assessed with 2D-gamma passing rates to determine the best planning methodology. RESULTS: Mean (±standard deviation) and median dose measured across the plate for the preclinical irradiator was 423.7 ± 8.5 cGy and 430.0 cGy. Mean percentage differences between standard and MBDCA dose calculations were 9.4% (HDR, 1 cm SCD), 0.43% (HDR, 0.4 cm SCD), and 2.4% (EBRT). Predicted and measured dose agreement was highest for MBDCAs for all modalities. CONCLUSION: A 3D-printed tissue culture platform can be used for multi-modality irradiation studies with great accuracy. This tool will facilitate preclinical studies to reveal biologic differences between clinically relevant radiation modalities.

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PURPOSE: We aim to investigate perioperative and subacute postoperative complications in patients undergoing LDR or HDR monotherapy for prostate cancer. We hypothesize a low rate of complications, and a favorable toxicity profile in patients treated with HDR compared to LDR. MATERIALS AND METHODS: A prospectively collected institutional database was queried for patients treated with HDR or LDR prostate monotherapy between 1998 and 2021. Toxicities were determined per CTCAE. Claims based billing codes were obtained to identify additional events. Events occurring within 4 months of treatment were defined as perioperative or subacute postoperative complications. RESULTS: 759 patients were identified, 446 received LDR with 125I, and 313 received HDR with 192Ir. HDR patients had higher risk features: 75.7% with Gleason score 7+ versus 2.4% of LDR, and 16% with initial PSA 10+ ng/mL versus 2.7% of LDR. Toxicities were mild with the most common being grade 1 GU frequency and nocturia at ∼50%. HDR patients had significantly less grade 2 dysuria (2.6% vs. 9.0%), frequency (4.8% vs. 9.4%), hematuria (1.0% vs. 5.2%), nocturia (3.8% vs. 9.4%), and urinary obstructive symptoms (7.3% vs. 11.2%), all statistically significant. 11 (1.4%) patients had infection requiring antibiotics: 8 (1.8%) from the LDR group and 3 (1%) from the HDR group. Cardiopulmonary events were low at <2% overall, without difference between HDR and LDR. CONCLUSIONS: Overall toxicity rates support the safety of prostate brachytherapy. HDR monotherapy is associated with significantly less perioperative and subacute postoperative GU events when compared to LDR monotherapy. Cardiopulmonary events were equally rare in both groups.

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Objective. The FLASH effect can potentially be used to improve the therapeutic ratio of radiotherapy (RT) through delivery of Ultra-high-dose-rate (UHDR) irradiation. Research is actively being conducted to translate UHDR-RT and for this purpose the Mobetron is capable of producing electron beams at both UHDR and conventional dose rates for FLASH research and translation. This work presents commissioning of an UHDR Mobetron with end-to-end tests developed for preclinical research.Approach. UHDR electron beams were commissioned with an efficient approach utilizing a 3D-printed water tank and film to fully characterize beam characteristics and dependences on field size, pulse width (PW) and pulse repetition frequency (PRF). This commissioning data was used to implement a beam model using the GAMOS Monte Carlo toolkit for the preclinical research. Then, the workflow for preclinical FLASH irradiation was validated with end-to-end tests delivered to a 3D-printed mouse phantom with internal inhomogeneities.Main results.PDDs, profiles and output factors acquired with radiochromic films were precisely measured, with a PRF that showed little effect on the UHDR beam energy and spatial characteristics. Increasing PW reduced theDmaxand R50by 2.08 mmµs-1and 1.28 mmµs-1respectively. An end-to-end test of the preclinical research workflow showed that both profiles in head-foot and lateral directions were in good agreement with the MC calculations for the heterogeneous 3D printed mouse phantom with Gamma index above 93% for 2 mm/2% criteria, and 99% for 3 mm/3%.Significance. The UHDR Mobetron is a versatile tool for FLASH preclinical research and this comprehensive beam model and workflow was validated to meet the requirements for conducting translational FLASH research.

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PURPOSE: This study investigated the potential of a commercially available plastic scintillator, the Exradin W2, as a real-time dosimeter for ultra-high-dose-rate (UHDR) electron beams. This work aimed to characterize this system's performance under UHDR conditions and addressed limitations inherent to other conventional dosimetry systems. METHODS AND MATERIALS: We assessed the W2's performance as a UHDR electron dosimeter using a 16 MeV UHDR electron beam from the FLASH research extension (FLEX) system. Additionally, the vendor provided a beta firmware upgrade to better handle the processing of the high signal generated in the UHDR environment. We evaluated the W2 regarding dose-per-pulse, pulse repetition rate, charge versus distance, and pulse linearity. Absorbed dose measurements were compared against those from a plane-parallel ionization chamber, optically stimulated luminescent dosimeters and radiochromic film. RESULTS: We observed that the 1 × 1 mm W2 scintillator with the MAX SD was more suitable for UHDR dosimetry compared to the 1 × 3 mm W2 scintillator, capable of matching film measurements within 2% accuracy for dose-per-pulse up to 3.6 Gy/pulse. The W2 accurately ascertained the inverse square relationship regarding charge versus virtual source distance with R2 of ∼1.00 for all channels. Pulse linearity was accurately measured with the W2, demonstrating a proportional response to the delivered pulse number. There was no discernible impact on the measured charge of the W2 when switching between the available repetition rates of the FLEX system (18-180 pulses/s), solidifying consistent beam output across pulse frequencies. CONCLUSIONS: This study tested a commercial plastic scintillator detector in a UHDR electron beam, paving the way for its potential use as a real-time, patient-specific dosimetry tool for future FLASH radiotherapy treatments. Further research is warranted to test and improve the signal processing of the W2 dosimetry system to accurately measure in UHDR environments using exceedingly high dose-per-pulse and pulse numbers.

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Objective.Detectors that can provide accurate dosimetry for microbeam radiation therapy (MRT) must possess intrinsic radiation hardness, a high dynamic range, and a micron-scale spatial resolution. In this work we characterize hydrogenated amorphous silicon detectors for MRT dosimetry, presenting a novel combination of flexible, ultra-thin and radiation-hard features.Approach.Two detectors are explored: an n-type/intrinsic/p-type planar diode (NIP) and an NIP with an additional charge selective layer (NIP + CSC).Results.The sensitivity of the NIP + CSC detector was greater than the NIP detector for all measurement conditions. At 1 V and 0 kGy under the 3T Cu-Cu synchrotron broadbeam, the NIP + CSC detector sensitivity of (7.76 ± 0.01) pC cGy-1outperformed the NIP detector sensitivity of (3.55 ± 0.23) pC cGy-1by 219%. The energy dependence of both detectors matches closely to the attenuation coefficient ratio of silicon against water. Radiation damage measurements of both detectors out to 40 kGy revealed a higher radiation tolerance in the NIP detector compared to the NIP + CSC (17.2% and 33.5% degradations, respectively). Percentage depth dose profiles matched the PTW microDiamond detector's performance to within ±6% for all beam filtrations except in 3T Al-Al due to energy dependence. The 3T Cu-Cu microbeam field profile was reconstructed and returned microbeam width and peak-to-peak values of (51 ± 1)µm and (405 ± 5)µm, respectively. The peak-to-valley dose ratio was measured as a function of depth and agrees within error to the values obtained with the PTW microDiamond. X-ray beam induced charge mapping of the detector revealed minimal dose perturbations from extra-cameral materials.Significance.The detectors are comparable to commercially available dosimeters for quality assurance in MRT. With added benefits of being micron-sized and possessing a flexible water-equivalent substrate, these detectors are attractive candidates for quality assurance,in-vivodosimetry and in-line beam monitoring for MRT and FLASH therapy.

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Introduction: FLASH radiotherapy (RT) has emerged as a promising modality, demonstrating both a normal tissue sparing effect and anticancer efficacy. We have previously reported on the safety and efficacy of single fraction FLASH RT in the treatment of oral tumors in canine cancer patients, showing tumor response but also a risk of radiation-induced severe late adverse effects (osteoradionecrosis) for doses ≥35 Gy. Accordingly, the objective in this study was to investigate if single fraction high dose FLASH RT is safe for treating non-oral tumors. Methods: Privately-owned dogs with superficial tumors or microscopic residual disease were included. Treatment was generally delivered as a single fraction of 15-35 Gy 10 MeV electron FLASH RT, although two dogs were re-irradiated at a later timepoint. Follow-up visits were conducted up to 12 months post-treatment to evaluate treatment efficiency and adverse effects. Results: Fourteen dogs with 16 tumors were included, of which nine tumors were treated for gross disease whilst seven tumors were treated post-surgery for microscopic residual disease. Four treatment sites treated with 35 Gy had ulceration post irradiation, which was graded as severe adverse effect. Only mild adverse effects were observed for the remaining treatment sites. None of the patients with microscopic disease experienced recurrence (0/7), and all patients with macroscopic disease showed either a complete (5/9) or a partial response (4/9). Five dogs were euthanized due to clinical disease progression. Discussion: Our study demonstrates that single fraction high dose FLASH RT is generally safe, with few severe adverse effects, particularly in areas less susceptible to radiation-induced damage. In addition, our study indicates that FLASH has anti-tumor efficacy in a clinical setting. No osteoradionecrosis was observed in this study, although other types of high-grade adverse effects including ulcer-formations were observed for the highest delivered dose (35 Gy). Overall, we conclude that osteoradionecrosis following single fraction, high dose FLASH does not appear to be a general problem for non-oral tumor locations. Also, as has been shown previously for oral tumors, 30 Gy appeared to be the maximum safe dose to deliver with single fraction FLASH RT.

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BACKGROUND: Single-dose high-dose-rate brachytherapy (SD-HDR-BT) was compared to two or three fraction HDR BT in intermediate and high-risk localized prostate cancer with median follow-up of 10 years. MATERIALS AND METHODS: 293 patients received 1 × 19Gy or 1 × 20Gy (Group A = 49), 2 × 13Gy (Group B = 138), or 3 × 10.5 Gy (Group C = 106) HDR BT. The primary endpoint was biochemical relapse-free interval (bRFI). Late genitourinary (GU) and gastrointestinal (GI) morbidity used RTOG scales and the International Prostate Symptom Score (IPSS). Freedom from biochemical relapse (bRFI), overall survival (OS) and GU, GI and IPSS morbidity were calculated using Kaplan-Meier (K-M) method and log-rank test. Univariate and multivariate hazard ratios (HR) were obtained using Cox's proportional hazard. RESULTS: At 10 years, K-M estimates of bRFI were 64 % (Group A), 72 % (Group B), and 76 % (Group C) (p = 0.2). No statistically significant difference was seen in OS. In multivariate analysis risk-category and ADT administration, but not dose, were significant predictors of relapse (p = 0.0003 and 0.03, respectively). At ten years, GU grade 3 events were 8 % (A), 2 % (B) and 13 % (C); (p = 0.01). IPSS ≥ 20 was 31 % (A), 20 % (B) and 23 % (C); (p = 0.6) and grade 3 GI was 0 % in groups A and B and 2 % in C; (p = 0.3). No GU or GI grade-4 events were observed. Pre-treatment IPSS was a highly significant predictor of failure in multivariate analysis. CONCLUSIONS: Long-term outcome data show reduced but not statistically significant difference in PSA control, and no difference in overall survival, between SD-HDR-BT and 2 or 3 fractions of HDR-BT.

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Surface mould brachytherapy is a conformal radiotherapy technique that can deliver high dose to the target while sparing nearby normal structures, Here, we aim to describe the procedurals details for high-dose rate (HDR) surface mould brachytherapy in sebaceous carcinoma of eyelid in a 54-year old lady. She was hesitant for surgery and any form of invasive intervention like interstitial brachytherapy. So, she was treated with surface mould HDR brachytherapy to a total dose of 52 Gy in 13 fractions at a dose of 4 Gy per fraction delivered twice daily using Iridium-192 isotope with no acute side effects. She was evaluated on a weekly basis for any radiation side effects and now she is disease-free for 6 months post-treatment with only mild dry eye. A detailed step-by-step procedure of surface mould technique, simulation procedure, dose prescription, planning, plan evaluation and treatment has been described in this paper. Surface mould HDR brachytherapy can be safely used as organ preserving modality of treatment for eyelid carcinoma.

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PURPOSE: Until March 2018, patients with high-risk localized prostate cancer had been administered high-dose-rate brachytherapy (HDR-BT) combined with external beam radiotherapy (EBRT) without additional hormone therapy (HT) at our institution. In this study, we aimed to evaluate long-term outcomes of this treatment. MATERIALS AND METHODS: Patients with prostate cancer who received HDR-BT and EBRT between April 1997 and March 2021 and who were followed up for at least 6 months were included in the study. High-risk groups were classified into five levels according to the National Comprehensive Cancer Network guidelines. The EBRT and HDR-BT doses were 39-45 Gy/13-25 fractions. and 16.5-22 Gy/2-4 fractions, respectively. None of the patients received HT during initial treatment. The Kaplan-Meier method was used to estimate biochemical freedom from failure (bFFF), cause-specific survival (CSS), and overall survival (OS) rates. Biochemical failure was also determined. RESULTS: Seventy-two patients were enrolled in the study, with a median follow-up of 91.9 months. The median age and initial prostate-specific antigen (iPSA) level were 71 years and 10.95 ng/mL, respectively. The median biologically effective dose for HDR-BT plus EBRT was 270.3 Gy. The 5- and 7-year bFFF, CSS, and OS rates were 85.2 and 74.2%, 100 and 100%, and 95.7 and 91.9%, respectively. Only the iPSA ≤ 20 group was associated with the higher bFFF rate. The 7-year bFFF rates in the groups with iPSA ≤ 20 and iPSA > 20 were 86.6 and 48.6%, respectively. CONCLUSION: HDR-BT plus EBRT without HT might be an alternative treatment option for patients with high-risk localized prostate cancer and iPSA levels ≤ 20. Further studies are required to validate the efficacy of this treatment strategy.

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Locally advanced cervical cancers are often treated with palliative intent due to concerns that the tumor is too far advanced or too large to be treated curatively. Also, patients greater than 65 years of age with cervical cancer are sometimes regarded as being too old or too frail to be cured with combined radiation and chemotherapy. These patients are often treated with radiation alone or with palliative therapy. Understanding the treatment modalities for cervical cancer is essential, as they can be complex and unique to each patient's specific diagnosis. This case report aims to describe the dramatic response to treatment with combined radiation and chemotherapy for a patient greater than 65 years of age with pelvis-filling cervical cancer with right-sided hydronephrosis. After a five-week course of concurrent chemoradiation, the cervical mass radiographically completely disappeared, with no evidence of disease noted on pelvic MRI.

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BACKGROUND: In vivo dosimetry (IVD) is rarely performed in brachytherapy (BT), allowing potential dose misadministration to go unnoticed. This study presents a clinical routine-calibration method of detectors for IVD in high (HDR) and pulsed dose rate (PDR) Ir-192 BT. PURPOSE: To evaluate the dosimetric precision and feasibility of an in-clinic calibration routine of detectors for IVD in afterloading BT. METHODS: Calibrations were performed in a PMMA phantom with two needles inserted 20 mm apart. The source was loaded in one of the needles at 15 dwells for 10 s. The detector was placed in the other needle, and its signal was recorded. The mean signal at each dwell position was fitted to the expected dose rate with the calibration factor and the detector's longitudinal position being free parameters. The method was tested with an inorganic scintillation detector using one Ir-192 FlexiSource HDR and two Ir-192 GammaMedPlus PDR sources and followed by validation measurements in water. RESULTS: The standard measurement uncertainty (k = 1) of the calibration factor in absolute terms (Gy/s) was 3.2/3.4% for the HDR/PDR source. The uncertainty was dominated by source strength uncertainty, and the precision of the method was <1%. The mean ± 1SD of the difference in measured and expected dose rate during validation was 1.5 ± 4.7% (HDR) and 0.0 ± 4.1% (PDR) with a positional uncertainty in the setup of 0.33/0.23 mm (HDR/PDR) (k = 1). CONCLUSION: A precise and feasible in-clinic calibration method for IVD and source strength consistency tests in BT was presented.

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