Cardiac radioablation of incessant ventricular tachycardia in patients with terminal heart failure under permanent left ventricular assist device therapy-description of two cases.

PURPOSE: Cardiac radioablation (cRA) using a stereotactic single-session radioablative approach has recently been described as a possible treatment option for patients with otherwise untreatable recurrent ventricular tachycardia (VT). There is very limited experience in cRA for patients undergoing left ventricular assist device (LVAD) therapy. We present clinical experiences of two patients treated with cRA for incessant VT under long-term LVAD therapy. METHODS: Two male patients (54 and 61 years old) with terminal heart failure under LVAD therapy (both patients for 8 years) showed incessant VT despite extensive antiarrhythmic drug therapy and repeated catheter ablation. cRA with a single dose of 25 Gy was applied as a last resort strategy under compassionate use in both patients following an electroanatomical mapping procedure. RESULTS: Both patients displayed ongoing VT during and after the cRA procedure. Repeated attempts at post-procedural rhythm conversion failed in both patients; however, one patient was hemodynamically stabilized and could be discharged home for several months before falling prey to a fatal bleeding complication. The second patient initially stabilized for a few days following cRA before renewed acceleration of running VT required bilateral ablation of the stellate ganglion; the patient died 50 days later. No immediate side effects of cRA were detected in either patient. CONCLUSION: cRA might serve as a last resort strategy for patients with terminal heart failure undergoing LVAD therapy and displaying incessant VT. Intermediate- and long-term outcomes of these seriously ill patients often remain poor; therefore, best supportive care strategies should also be evaluated as long as no clear beneficial effects of cRA procedures can be shown. For patients treated with cRA under running ventricular rhythm abnormality, strategies for post-procedural generation of stabilized rhythm have to be established.

68Ga-DOTATOC-PET/MRI-A Secure One-Stop Shop Imaging Tool for Robotic Radiosurgery Treatment Planning in Patients with Optic Nerve Sheath Meningioma.

Optic nerve sheath meningiomas (ONSM) are rare but can lead to irreversible blindness. Hybrid imaging may enhance tumor delineation and diagnostic accuracy via receptor binding. However, relevant clinical data for ONSM are lacking. We evaluated the feasibility of receptor-based hybrid imaging prior to robotic radiosurgery (RRS). We retrospectively analyzed all of our institution's patients with suspected ONSM who underwent combined positron emission tomography and magnetic resonance imaging (PET/MRI) with gallium-68-labeled (DOTA0-Phe1-Tyr3) octreotide (Ga68-DOTATOC) before RRS between 2018 and 2019. Eight patients with ten suspected ONSM (female = 7; median age, 51.2 years; IQR, 43.0-66.0) were included. Nine out of ten ONSM were deemed PET-positive with a median standard uptake value (SUV) max of 5.6 (IQR, 2.6-7.8). For all nine ONSM that presented 68Ga-DOTATOC uptake, hybrid PET/MRI was used for target volume contouring prior to RSS. At a median follow-up of 11.7 months (IQR, 9.4-16.4), tumor control was achieved in all patients. Radiosurgery resulted in the improvement of visual acuity in two of eight patients, whereas six showed stable vision. Ga68-DOTATOC-PET/MRI can be used for target volume contouring prior to RRS for ONSM as it enables safe treatment planning and improves diagnostic accuracy.

Establishment and Validation of CyberKnife Irradiation in a Syngeneic Glioblastoma Mouse Model.

CyberKnife stereotactic radiosurgery (CK-SRS) precisely delivers radiation to intracranial tumors. However, the underlying radiobiological mechanisms at high single doses are not yet fully understood. Here, we established and evaluated the early radiobiological effects of CK-SRS treatment at a single dose of 20 Gy after 15 days of tumor growth in a syngeneic glioblastoma-mouse model. Exact positioning was ensured using a custom-made, non-invasive, and trackable frame. One superimposed target volume for the CK-SRS planning was created from the fused tumor volumes obtained from MRIs prior to irradiation. Dose calculation and delivery were planned using a single-reference CT scan. Six days after irradiation, tumor volumes were measured using MRI scans, and radiobiological effects were assessed using immunofluorescence staining. We found that CK-SRS treatment reduced tumor volume by approximately 75%, impaired cell proliferation, diminished tumor vasculature, and increased immune response. The accuracy of the delivered dose was demonstrated by staining of DNA double-strand breaks in accordance with the planned dose distribution. Overall, we confirmed that our proposed setup enables the precise irradiation of intracranial tumors in mice using only one reference CT and superimposed MRI volumes. Thus, our proposed mouse model for reproducible CK-SRS can be used to investigate radiobiological effects and develop novel therapeutic approaches.