Peripheral Doses Beyond Electron Applicators in Conventional C-Arm Linear Accelerators: A Systematic Literature Review.

Background: This review investigates peripheral dose levels in electron beam treatments, comparing different manufacturers including Varian, Elekta, and Siemens. Accurate measurement of peripheral dose is vital for patient safety and precise radiation delivery in radiation therapy. Methods: This review followed PRISMA standards, conducting a comprehensive literature search from 1978 to July 2023. Emphasis was on identifying studies analyzing peripheral doses related to various electron beam energies, beam angle, field sizes, cutouts, and applicator combinations. Three major databases including PubMed, Web of Science, and Scopus were searched. Results: A total of 7 articles were included in this review. Strategies such as bolus materials, personalized cutouts, and optimal treatment procedures have all been developed to reduce peripheral radiation exposure and enhance patient safety. Ongoing research in this field is focused on further minimizing the risks associated with out-of-field radiation by improving dose delivery systems. Conclusion: The literature emphasizes importance of precision in electron beam radiation therapy, highlighting the critical need for managing peripheral doses and optimizing hardware to ensure patient safety. It advocates for the use of advanced tools and protocols to maintain a balance between effective treatment while protecting healthy tissues. Continuous research, careful treatment planning, and effective management of peripheral doses are essential.

The Various Roles of PEDF in Cancer.

Pigment epithelium-derived factor (PEDF) is a natural immunomodulator, anti-inflammatory, anti-angiogenic, anti-tumour growth and anti-metastasis factor, which can enhance tumour response to PEDF but can also conversely have pro-cancerous effects. Inflammation is a major cause of cancer, and it has been proven that PEDF has anti-inflammatory properties. PEDF's functional activity can be investigated through measuring metastatic and metabolic biomarkers that will be discussed in this review.

Stereotactic body radiotherapy for early-stage lung cancer: a systematic review on the choice of photon energy and linac flattened/unflattened beams.

SBRT is an effective local treatment for patients with early-stage non-small cell lung cancer (NSCLC). This treatment is currently used in patients who have poor lung function or who decline surgery. As SBRT usually has small PTV margins, reducing the beam-on-time (BOT) is beneficial for accurate dose delivery by minimising intrafraction motion as well as improved patient comfort. Removal of the linear accelerator flattening filter can provide a higher dose rate which results in a faster treatment. In addition, the choice of photon energy can also affect the dose distribution to the target and the organs-at-risk (OAR). In this systematic review, studies analysing the choice of various photon beam energies, with a flattening filter or flattening filter free (FFF), were compared for their overall dosimetric benefit in the SBRT treatment for early-stage NSCLC. It was found that FFF treatment delivers a comparatively more conformal dose distribution, as well as a better homogeneity index and conformity index, and typically reduces BOT by between 30 and 50%. The trade-off may be a minor increase in monitor units for FFF treatment found in some studies but not others. Target conformity and OAR sparing, particularly lung doses appear better with 6MV FFF, but 10MV FFF was marginally more advantageous for skin sparing and BOT reduction. The favourable beam modality for clinical use would depend on the individual case, for which tumour size and depth, radiotherapy technique, as well as fractionation scheme need to be taken into account.

Transformer CycleGAN with uncertainty estimation for CBCT based synthetic CT in adaptive radiotherapy.

Objective. Clinical implementation of synthetic CT (sCT) from cone-beam CT (CBCT) for adaptive radiotherapy necessitates a high degree of anatomical integrity, Hounsfield unit (HU) accuracy, and image quality. To achieve these goals, a vision-transformer and anatomically sensitive loss functions are described. Better quantification of image quality is achieved using the alignment-invariant Fréchet inception distance (FID), and uncertainty estimation for sCT risk prediction is implemented in a scalable plug-and-play manner.Approach. Baseline U-Net, generative adversarial network (GAN), and CycleGAN models were trained to identify shortcomings in each approach. The proposed CycleGAN-Best model was empirically optimized based on a large ablation study and evaluated using classical image quality metrics, FID, gamma index, and a segmentation analysis. Two uncertainty estimation methods, Monte-Carlo Dropout (MCD) and test-time augmentation (TTA), were introduced to model epistemic and aleatoric uncertainty.Main results. FID was correlated to blind observer image quality scores with a Correlation Coefficient of -0.83, validating the metric as an accurate quantifier of perceived image quality. The FID and mean absolute error (MAE) of CycleGAN-Best was 42.11 ± 5.99 and 25.00 ± 1.97 HU, compared to 63.42 ± 15.45 and 31.80 HU for CycleGAN-Baseline, and 144.32 ± 20.91 and 68.00 ± 5.06 HU for the CBCT, respectively. Gamma 1%/1 mm pass rates were 98.66 ± 0.54% for CycleGAN-Best, compared to 86.72 ± 2.55% for the CBCT. TTA and MCD-based uncertainty maps were well spatially correlated with poor synthesis outputs.Significance. Anatomical accuracy was achieved by suppressing CycleGAN-related artefacts. FID better discriminated image quality, where alignment-based metrics such as MAE erroneously suggest poorer outputs perform better. Uncertainty estimation for sCT was shown to correlate with poor outputs and has clinical relevancy toward model risk assessment and quality assurance. The proposed model and accompanying evaluation and risk assessment tools are necessary additions to achieve clinically robust sCT generation models.

Risk of cardiac implantable device malfunction in cancer patients receiving proton therapy: an overview.

Age is a risk factor for both cardiovascular disease and cancer, and as such radiation oncologists frequently see a number of patients with cardiac implantable electronic devices (CIEDs) receiving proton therapy (PT). CIED malfunctions induced by PT are nonnegligible and can occur in both passive scattering and pencil beam scanning modes. In the absence of an evidence-based protocol, the authors emphasise that this patient cohort should be managed differently to electron- and photon- external beam radiation therapy (EBRT) patients due to distinct properties of proton beams. Given the lack of a PT-specific guideline for managing this cohort and limited studies on this important topic; the process was initiated by evaluating all PT-related CIED malfunctions to provide a baseline for future reporting and research. In this review, different modes of PT and their interactions with a variety of CIEDs and pacing leads are discussed. Effects of PT on CIEDs were classified into a variety of hardware and software malfunctions. Apart from secondary neutrons, cumulative radiation dose, dose rate, CIED model/manufacturer, distance from CIED to proton field, and materials used in CIEDs/pacing leads were all evaluated to determine the probability of malfunctions. The importance of proton beam arrangements is highlighted in this study. Manufacturers should specify recommended dose limits for patients undergoing PT. The establishment of an international multidisciplinary team dedicated to CIED-bearing patients receiving PT may be beneficial.

Radiotherapy planning of spine and pelvis using single-energy metal artifact reduction corrected computed tomography sets.

Metal artifacts produce incorrect Hounsfield units and impact treatment planning accuracy. This work evaluates the use of single-energy metal artifact reduction (SEMAR) algorithm for treatment planning by comparison to manual artifact overriding. CT datasets of in-house 3D-printed spine and pelvic phantoms with and without metal insert(s) and two treated patients with metal implants were analysed. CT number accuracy improved with the use of SEMAR filter: root mean square deviation (RMSD) from reference (without metal) reduced by 35.4 in spine and 98.8 in hip. The plan dose volume histograms (DVHs) and dosimetric measurements showed comparable results. SEMAR reconstruction improved planning efficiency.

An in-depth review of retrospective studies to assess the role of vascular brachytherapy for the treatment of complex patients with multiple risk factors for DES-ISR.

BACKGROUND: Vascular brachytherapy (VBT) used to be an effective treatment modality for management of in-stent stenosis but was superceded by drug eluting stents (DES) which had shown a greater efficacy. However, there is no clear evidence to support superior management for in-stent restenosis (ISR) which continues to be a challenge. METHODS: We conducted a systematic review of the literature and appraised PubMed, Medline, Web of science, ProQuest and Cochrane databases from 2000 to 2020. We assessed comparative outcomes including efficacy (as assessed by measuring major adverse cardiac events, target vessel revascularisation, target lesion revascularisation, all-cause mortality, target lesion myocardial infarction and stent thrombosis) and safety of VBT. RESULTS: Of 1083 records obtained, a total of 8 retrospective studies met the inclusion criteria. In the included studies, major adverse cardiac events (MACE) rates ranged from 10% to 17.5% in the VBT group compared to 14.1% to 28.2% in the re-DES group at one year follow up. There were lower rates of target vessel revascularisation (VBT 10-22.8%; control 18-22.9%) and target lesion revascularisation (VBT 10-14.1%, Control 8-22.1%) between the VBT and re-DES groups. There were significantly low rates of all-cause mortality (1-5.4%), target lesion myocardial infarction (0-7%) and stent thrombosis (0-2.1%) in the VBT group at one year. CONCLUSIONS: VBT is considered to be an effective and safe treatment strategy in complex patients with multiple risk factors for DES-ISR in initial reports. There are no long-term comparison studies available beyond 1 year. There is a need for randomised controlled trials to objectively assess the role of VBT compared to DES and drug coated balloons.

Circulating Tumour Cells (CTC), Head and Neck Cancer and Radiotherapy; Future Perspectives.

Head and neck cancer is the seventh most common cancer in Australia and globally. Despite the current improved treatment modalities, there is still up to 50⁻60% local regional recurrence and or distant metastasis. High-resolution medical imaging technologies such as PET/CT and MRI do not currently detect the early spread of tumour cells, thus limiting the potential for effective minimal residual detection and early diagnosis. Circulating tumour cells (CTCs) are a rare subset of cells that escape from the primary tumour and enter into the bloodstream to form metastatic deposits or even re-establish themselves in the primary site of the cancer. These cells are more aggressive and accumulate gene alterations by somatic mutations that are the same or even greater than the primary tumour because of additional features acquired in the circulation. The potential application of CTC in clinical use is to acquire a liquid biopsy, by taking a reliable minimally invasive venous blood sample, for cell genotyping during radiotherapy treatment to monitor the decline in CTC detectability, and mutational changes in response to radiation resistance and radiation sensitivity. Currently, very little has been published on radiation therapy, CTC, and circulating cancer stem cells (CCSCs). The prognostic value of CTC in cancer management and personalised medicine for head and neck cancer radiotherapy patients requires a deeper understanding at the cellular level, along with other advanced technologies. With this goal, this review summarises the current research of head and neck cancer CTC, CCSC and the molecular targets for personalised radiotherapy response.

Hyperbaric oxygen therapy for chronic radiation-induced tissue injuries: Australasia's largest study.

AIM: Chronic radiation injuries, although uncommon, are associated with poor quality of life in oncology patients. The present study assesses the efficacy and safety of hyperbaric oxygen therapy in the management of chronic radiation-induced tissue injuries. METHODS: A retrospective analysis was performed in 276 consecutive patients treated with hyperbaric oxygen therapy for chronic radiation-induced tissue injuries at the Hyperbaric Medicine Unit, Townsville, Queensland, between March 1995 and March 2008. Of these patients, 189 (68%) had complete follow-up data and were assessed. RESULTS: A total of 265 events of chronic radiation tissue injury were experienced by the 189 patients treated with hyperbaric oxygen therapy. Osteoradionecrosis prophylaxis due to radiation-induced dental disease had an overall response rate of 96% (P=0.00003; Wilcoxon matched-pairs signed-rank test). The overall response rates for established osteoradionecrosis of mandible, soft tissue necrosis of head and neck, and xerostomia were 86% (P=0.00001), 85% (P=0.002) and 64% (P=0.0001), respectively. The overall response rates for soft tissue necrosis at other sites, chronic radiation proctitis and hemorrhagic cystitis were 84% (P=0.03), 95% (P=0.0001) and 85% (P=0.03), respectively. The total complication rate after hyperbaric oxygen therapy was 15.9%, comprising reversible ear barotrauma (10.6%), reversible ocular barotrauma (4.2%), dental complications (0.5%) and myocardial infarction (0.5%). CONCLUSION: Our study demonstrates that hyperbaric oxygen therapy can be effectively used in a variety of chronic radiation-induced tissue injuries; its favorable risk profile suggests it should be considered for patients with radiation-induced tissue injuries.

Efficacy and tolerability of weekly low-dose cisplatin concurrent with radiotherapy in head and neck cancer patients.

AIMS: In this retrospective analysis, we describe the efficacy and tolerability of weekly cisplatin 40 mg/m(2) used in concurrent chemoradiation of head and neck cancer at the Townsville Cancer Centre. METHODS: Review of medical records of patients who received radical chemoradiotherapy for head and neck cancer at Townsville Cancer Centre from 2003 to 2009. RESULTS: In all 102 patients were analysed, 62 of whom had definitive chemoradiation and the remainder adjuvant chemoradiotherapy. Median follow up was 20.1 months (range 5-86 months). Overall 68.6% of patients received 5 weeks or more of planned chemotherapy. Radiotherapy interruptions occurred in four (6.4%) patients. The rate of grade 3-4 adverse events was 51% including neutropenia (18.6%), mucositis (21.8%) and dysphagia (12.9%) and 30.7% of patients needed hospital admission to manage toxicities. For definitive and adjuvant groups, estimated 3-year survival was 64.5 and 71.5%, respectively, and estimated 3-year disease-specific survival rates were 70.3 and 81.6%, respectively. The 3-year overall survival for patients who received five or more cycles of chemotherapy was 75.2%, compared to 52.6% for those receiving fewer than five cycles (P = 0.018). CONCLUSION: Despite this is being a small retrospective study, survival figures and toxicity profiles of low dose weekly cisplatin are comparable to historical controls using high-dose regimens, hence justifying our approach. In addition, radiotherapy interruptions are minimized and cisplatin is easy to administer in outpatient settings. Future three-arm studies could include this regimen as the basis of treatment combined with targeted therapies.