CyberKnife Stereotactic Radiosurgery Research Articles

RADT-22. EFFICACY AND SAFETY OF CYBERKNIFE STEREOTACTIC RADIOSURGERY FOR OCCIPITAL CONDYLE METASTASIS

Abstract BACKGROUND Occipital condyle metastasis (OCM) is a rare condition characterized by severe occipital pain and neurological symptoms due to lower cranial nerve deficits, stemming from its anatomical location. Despite the widespread use of stereotactic radiosurgery (SRS) for cranial metastases, its specific impact on OCM remains underexplored. OBJECTIVE This study evaluates the efficacy and safety of CyberKnife SRS in treating OCM, focusing on symptom control and local tumor control. METHOD We retrospectively analyzed cases of OCM treated with SRS at our institute from 2012 to 2023, evaluating patient demographics, presenting symptoms, treatment parameters, and outcomes. Key measures included occipital pain, dysfunctions of cranial nerves IX, X, and XII, and local tumor control. RESULTS Eighteen patients (10 females) with a median age of 64 years (range: 40-79) were treated. Common presentations included occipital pain (44%) and lower cranial nerve deficits (28%). The median target volume was 6.95 cc (range: 0.95-72.7), and the median margin dose was 20 Gy (range: 16-40). The median follow-up period was 7 months (range: 1-44). Notably, only one patient experienced tumor recurrence and subsequently died from primary cancer progression five months after treatment. SRS achieved a 93.8% local tumor control rate over three years, with a median overall survival of 13 months. Among those presenting with symptoms, 87.5% reported pain relief, and 80% observed improvements in cranial nerve function. The only patient without clinical symptom improvement also had tumor recurrence. CONCLUSION CyberKnife SRS is a promising treatment for OCM, offering significant pain relief and improvement in neurological symptoms with excellent local control rates. This non-invasive therapy provides a valuable alternative to surgery, potentially enhancing the quality of life for patients with limited treatment options due to this challenging condition.

The Role of Ultrasound-Based Monitoring of Bladder Volume in Patients with Prostate Cancer during CyberKnife Stereotactic Radiosurgery

(1) Background: For patients irradiated due to prostate cancer, monitoring of bladder volume (BV) is crucial for accuracy of radiation delivery and minimizing exposure to surrounding healthy tissues. Due to the limited imaging capabilities of the CyberKnife system, ultrasound imaging plays a vital role in the monitoring of bladder filling. (2) Methods: A study was carried out in 142 prostate cancer patients treated with the CyberKnife system. Bladder ultrasound (US) was performed before each RTH session to assess real BV (rBV). The double US assessment of rBV was performed by two independent operators or a single operator during 177 and 495 RTH sessions, respectively, giving, in total, 1344 BV assessments. (3) Results: The mean BV in the first and second US assessment was 214.7 mL and 218.1 mL, respectively, while the mean planning bladder volume (pBV) was 340.8 mL. A pBV was significantly higher than an rBV. The mean difference between the US and CT assessment of BV was the smallest in the 100–349 mL group and the largest in the group above 349 mL. The Passing–Bablok regression results confirmed the reliability of the ultrasound (US) measurements. (4) Conclusions: The introduction of US-based BV assessment in patients irradiated due to prostate cancer using CyberKnife seems to be a crucial element in controlling the reproducibility of the treatment plan and should be a standard procedure. The pBV should be within the range of 200–300 mL. The US examination prior to CT scanning for planning is recommended to ensure the optimal range of BV for CT.

Calculating Optic Nerve Planning Organ at Risk Volume Margins for Stereotactic Radiosurgery Using Optic Nerve Motion determined using MRI.

The combination of sharp dose gradients in stereotactic radiosurgery (SRS) and minute optic nerve motion may significantly increase dose to the optic nerves when treating perioptic lesions. The aim of this study was to calculate optic nerve planning organ at risk volume (PRV) margins for CyberKnife SRS treatment planning. MRI scans were taken of 10 healthy volunteers looking left, right, up, down, and straight ahead to measure optic nerve motion. The measured optic nerve motion and the uncertainties in the technical accuracy of CyberKnife were used to calculate optic nerve PRV margins. Two optic nerve PRV margins were calculated: a non-isotropic margin of mL/R,PRV=3mm, mSup/Inf,PRV=2mm and mAnt/Post,PRV=1mm which considers the full range of motion measured in a worst case scenario; and an isotropic margin of mPRV=1mm which considers a scenario where patients are asked to look neutrally during imaging and treatment. Applying these PRVs to 8 historical sphenoid wing meningioma CyberKnife plans showed tolerance levels may be exceeded due to optic nerve motion. Optic nerve PRV margins may be needed in CyberKnife planning to reduce risk to the optic nerves. The use of a mPRV=1mm PRV to account for organ motion, along with instructing patients to hold their gaze neutrally during imaging and treatment, may be a suitable organ sparing strategy. Measured optic nerve motion and the technical accuracy of the CyberKnife system have been used to calculate optic nerve PRV margins.

Stereotactic Radiosurgery for Residual, Recurrent, and Metastatic Hemangiopericytomas: A Single-Institution Retrospective Experience.

Hemangiopericytomas are infrequent vascular tumors originating from Zimmermann pericytes. The conventional treatment involves gross total resection, followed by adjuvant radiotherapy. Nevertheless, their tendency to infiltrate dural sinuses, high vascularity, and anatomic complexity pose challenges for radical resection, leading to a significant risk of recurrence. Stereotactic radiosurgery (SRS) has emerged as a promising adjuvant therapy to address these challenges. Our study provides the largest single-institutional retrospective, aiming to evaluate the effectiveness and safety of SRS as a treatment modality for residual, recurrent, and metastatic hemangiopericytomas. From 1998 to 2023, 27 patients with 101 tumors underwent CyberKnife SRS at Stanford University Medical Center. The median age was 51 years at the time of treatment. The median follow-up period from SRS was 103 months (range: 6-250). All patients underwent upfront surgical resection. The median tumor volume was 1.5 cc. The median single-fraction equivalent dose was 19 Gy. The SRS was administered at the 76% of the median isodose line (range: 64-89). Of the 101 treated tumors, 24 (23.8%) progressed with a median time to recurrence of 30 months. At 10 years, the rates of local tumor control (LTC), overall survival (OS), and progression-free survival (PFS) were 74.3%, 80.8%, and 67%, respectively. In patients with metastatic lesions, the LTC rates were significantly greater when compared with those with residual or recurrent tumors. There was no significant difference between patients with residual, recurrent, and metastatic hemangiopericytomas in OS and PFS. Notably, no cases of radiation-induced adverse events were detected. SRS leads to excellent LTC, PFS, and OS at 10 years with negligible risk for adverse events. Therefore, it is an effective and safe management modality for patients with residual, recurrent, and metastatic hemangiopericytomas.

Recurrent choroid plexus carcinoma treated with CyberKnife radiosurgery: illustrative case.

Choroid plexus carcinomas (CPCs) are rare malignant brain tumors primarily affecting children younger than 2 years old. These tumors originate from the choroid plexus epithelium and are a subtype of choroid plexus tumors, which account for 1%-4% of pediatric brain tumors. Although CPCs often show a notably high recurrence rate after surgery, the standard treatment approach remains gross-total resection (GTR) of the tumor, given the lack of clinical data supporting the effectiveness of adjunct treatment options such as radiotherapy or chemotherapy. A 16-year-old female with a history of a recurrent cranial CPC resistant to surgery and radiotherapy was treated with CyberKnife stereotactic radiosurgery (SRS), following resection. The procedures successfully maintained local disease control for 41 months; however, there was a subsequent recurrence, ultimately leading to the death of the patient. CPC treatment remains challenging. SRS can be used as a viable adjunct to surgery, which remains the gold standard, although it can also be considered for nonsurgical candidates or when GTR cannot be achieved. Nevertheless, it is crucial to conduct additional research to explore diverse approaches for radiosurgery, including its role as the primary treatment modality versus its combination with surgery, radiotherapy, or chemotherapy. https://thejns.org/doi/10.3171/CASE23748.

The Role of CyberKnife Stereotactic Radiosurgery in Recurrent Cranial Medulloblastomas across Pediatric and Adult Populations.

Background/Objectives: Medulloblastoma is the most common malignant brain tumor in children. In recent decades, the therapeutic landscape has undergone significant changes, with stereotactic radiosurgery (SRS) emerging as a promising treatment for recurrent cases. Our study provides a comprehensive analysis of the long-term efficacy and safety of SRS in recurrent medulloblastomas across both pediatric and adult patients at a single institution. Methods: We retrospectively reviewed the clinical and radiological records of patients who underwent CyberKnife SRS for recurrent cranial medulloblastomas at our institution between 1998 and 2023. Follow-up data were available for 15 medulloblastomas in 10 patients. The cohort comprised eight pediatric patients (ages 3-18) and two adult patients (ages 19-75). The median age at the time of SRS was 13 years, the median tumor volume accounted for 1.9 cc, the median biologically equivalent dose (BED) was 126 Gy, and the single-fraction equivalent dose (SFED) was 18 Gy. The SRS was administered at 75% of the median isodose line. Results: Following a median follow-up of 39 months (range: 6-78), 53.3% of the medulloblastomas progressed, 13.3% regressed, and 33.3% remained stable. The 3-year local tumor control (LTC) rate for all medulloblastomas was 65%, with lower rates observed in the adult cohort (50%) and higher rates in pediatric patients (67%). The 3-year overall survival (OS) rate was 70%, with significantly higher rates in pediatric patients (75%) compared to adult patients (50%). The 3-year progression-free survival (PFS) rate was 58.3%, with higher rates in pediatric patients (60%) compared to adult patients (50%). Two pediatric patients developed radiation-induced edema, while two adult patients experienced radiation necrosis at the latest follow-up, with both adult patients passing away. Conclusions: Our study provides a complex perspective on the efficacy and safety of CyberKnife SRS in treating recurrent cranial medulloblastomas across pediatric and adult populations. The rarity of adverse radiation events (AREs) underscores the safety profile of SRS, reinforcing its role in enhancing treatment outcomes. The intricacies of symptomatic outcomes, intertwined with factors such as age, tumor location, and prior surgeries, emphasize the need for personalized treatment approaches. Our findings underscore the imperative for ongoing research and the development of more refined treatment strategies for recurrent medulloblastomas. Given the observed disparities in treatment outcomes, a more meticulous tailoring of treatment approaches becomes crucial.

Navigating alopecia: Practical guidelines for minimizing hair loss in CyberKnife stereotactic radiosurgery for calvarial or scalp tumors

Navigating alopecia: Practical guidelines for minimizing hair loss in CyberKnife stereotactic radiosurgery for calvarial or scalp tumors

Stereotactic Radiosurgery for Ependymoma in Pediatric and Adult Patients: A Single-Institution Experience.

Ependymoma is commonly classified as World Health Organization grade 2 with the anaplastic variant categorized as grade 3. Incomplete resection or anaplastic features can result in unfavorable outcomes. Stereotactic radiosurgery (SRS) provides a minimally invasive approach for recurrent ependymomas. Our study investigates the efficacy and safety of SRS for grade 2 and 3 ependymomas in pediatric and adult populations. We conducted a retrospective analysis on 34 patients with 75 ependymomas after CyberKnife SRS between 1998 and 2023. Fourteen were pediatric (3-18 years), and 20 were adult (19-75 years) patients. The median age was 21 years, and the median tumor volume was 0.64 cc. The median single-fraction equivalent dose was 16.6 Gy, with SRS administered at 77% of the median isodose line. After a median follow-up of 42.7 months (range: 3.8-438.3), 22.7% of ependymomas progressed. The 5-year local tumor control rate was 78.1%, varying between 59.6% and 90.2% for children and adults, with grade 2 at 85.9% compared with 58.5% for grade 3 tumors. The 5-year overall survival rate was 73.6%, notably higher in adults (94.7%) than in children (41%), and 100% for grade 2 but decreased to 35.9% for grade 3 patients. The 5-year progression-free survival rate was 68.5%, with 78.3% and 49.2% for adults and children, respectively, and a favorable 88.8% for grade 2, contrasting with 32.6% for grade 3 patients. Symptom improvement was observed in 85.3% of patients. Adverse radiation effects occurred in 21.4% of pediatric patients. Our study supports SRS as a viable modality for pediatric and adult patients with grade 2 and 3 ependymomas. Despite lower local tumor control in pediatric and grade 3 cases, integrating SRS holds promise for improved outcomes. Emphasizing careful patient selection, personalized treatment planning, and long-term follow-up is crucial for optimal neurosurgical outcomes.

CyberKnife stereotactic radiosurgery for extramedullary plasmacytoma in the external auditory canal: illustrative case.

Plasmacytoma, a rare plasma cell disorder, often presents as a solitary or multiple tumors within the bone marrow or soft tissues, typically associated with multiple myeloma. Extramedullary plasmacytomas (EMPs), particularly those located in the external auditory canal (EAC), are exceedingly rare and pose significant treatment challenges given their location, anatomical complexity, and high risk of recurrence. The authors report the case of a 72-year-old male with a history of multiple myeloma, presenting with recurrent left EAC plasmacytoma. After initial conventional radiotherapy for the lesion, a recurrence was documented in 7 years. The patient subsequently underwent stereotactic radiosurgery, which proved successful, leading to complete resolution of the lesion without any long-term adverse effects or radiation-related complications over a 45-month period. This case is a unique instance of utilizing stereotactic radiosurgery for recurrent EMP in the EAC, highlighting its potential as an effective approach in managing complex plasmacytomas.

Cyberknife Stereotactic Radiosurgery for Trigeminal Neuralgia: A Single-Institution Retrospective Analysis of Clinical Outcomes

Abstract Introduction: CyberKnife stereotactic radiosurgery (CKSRS) is recognized as a highly efficient intervention for refractory trigeminal neuralgia (TN). Our study aims to evaluate the clinical outcomes of CKSRS in treating medically refractory TN. By assessing these results, we aim to understand CKSRS efficacy and its potential as an alternative for nonresponsive patients to traditional medical treatments. Methods: In a retrospective study carried out at my institution, 25 patients with refractory TN were treated between 2018 and 2020. Clinical outcomes, including pain control and hypoesthesia/numbness, were assessed at 6, 12, and 24 months after CKSRS. The study employed the Barrow Neurological Institute pain intensity and facial numbness scores acquired through a telephone questionnaire to assess pain relief and the onset of facial hypoesthesia, thus establishing the effectiveness of the treatment. Results: There were 14 male and 11 female patients. Among all the patients, 44% experienced relief from pain and were not on any medication for pain, whereas 52% reported occasional pain that did not require medication at the end of the study period. The adverse effect of CKSRS, facial numbness, was observed in 58% of patients as mild facial numbness and in 44% as bothersome facial numbness. Moreover, a higher dose of CKSRS administered to the trigeminal nerve was associated with statistically significant pain control (P < 0.05). Conclusion: The study concludes that CKSRS is a safe and effective treatment option for refractory TN. It is worth noting that the occurrence or progression of facial hypoesthesia posttreatment was identified as a predictor of prolonged pain relief.

Insights into the dosimetric and geometric characteristics of stereotactic radiosurgery for multiple brain metastases: A systematic review.

GammaKnife (GK) and CyberKnife (CK) have been the mainstay stereotactic radiosurgery (SRS) solution for multiple brain metastases (MBM) for several years. Recent technological advancement has seen an increase in single-isocentre C-arm linac-based SRS. This systematic review focuses on dosimetric and geometric insights into contemporary MBM SRS and thereby establish if linac-based SRS has matured to match the mainstay SRS delivery systems. The PubMed, Web of Science and Scopus databases were interrogated which yielded 891 relevant articles that narrowed to 20 articles after removing duplicates and applying the inclusion and exclusion criteria. Primary studies which reported the use of SRS for treatment of MBM SRS and reported the technical aspects including dosimetry were included. The review was limited to English language publications from January 2015 to August 2023. Only full-length papers were included in the final analysis. Opinion papers, commentary pieces, letters to the editor, abstracts, conference proceedings and editorials were excluded. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines were followed. The reporting of conformity indices (CI) and gradient indices, V12Gy, monitor units and the impact of translational and rotational shifts were extracted and analysed. The single-isocentre technique for MBM dominated recent SRS studies and the most studied delivery platforms were Varian. The C-arm linac-based SRS plan quality and normal brain tissue sparing was comparable to GK and CK and in some cases better. The most used nominal beam energy was 6FFF, and optimised couch and collimator angles could reduce mean normal brain dose by 11.3%. Reduction in volume of the healthy brain receiving a certain dose was dependent on the number and size of the metastases and the relative geometric location. GK and CK required 4.5-8.4 times treatment time compared with linac-based SRS. Rotational shifts caused larger changes in CI in C-arm linac-based single-isocentre SRS. C-arm linac-based SRS produced comparable MBM plan quality and the delivery is notably shorter compared to GK and CK SRS.

RADT-35. STEREOTACTIC RADIOSURGERY FOR RESIDUAL, RECURRENT, AND METASTATIC HEMANGIOPERICYTOMAS: A SINGLE INSTITUTION EXPERIENCE

Abstract INTRODUCTION Hemangiopericytomas are infrequent vascular tumors originating from Zimmermann pericytes. The conventional treatment approach involves gross total resection (GTR), followed by adjuvant radiotherapy. Nevertheless, due to their tendency to infiltrate dural sinuses, high degree of vascularity, and anatomic inaccessibility, radical resection may be challenging with substantial risk of recurrence. To address this challenge, stereotactic radiosurgery (SRS) has been proposed as a promising adjuvant therapy. Objectives Our study aims to evaluate the effectiveness and safety of SRS as a potential treatment modality in patients with residual, recurrent, and metastatic hemangiopericytomas. METHODS From 1998 to 2023, 27 patients with 101 tumors underwent CyberKnife SRS at Stanford University Medical Center. The median age was 51 years at the time of treatment. The median follow-up period from SRS was 103 months (range: 6-250). All patients underwent upfront surgical resection. The median tumor volume was 1.5 cc. The median single-fraction equivalent dose (SFED) was 19 Gy. The SRS was administered at the 76% of the median isodose line (range: 64-89). RESULTS Of the 101 treated tumors, 24 (23.8%) progressed with a median time to recurrence of 30 months. At 10 years, the rates of local tumor control (LTC), overall survival (OS), and progression-free survival (PFS) were 74.3%, 80.8%, and 67%, respectively. In patients with residual lesions, the LTC rates were significantly greater when compared to those with residual or metastatic tumors. There was no significant difference between patients with residual, recurrent, and metastatic hemangiopericytomas in OS and PFS. Notably, no cases of radiation-induced adverse events were detected. CONCLUSION Our study provides the largest single-institutional retrospective series with hemangiopericytomas treated with SRS. SRS leads to excellent LTC, PFS, and OS at 10 years with negligible risk for adverse events. Therefore, it is an effective and safe management modality for patients with residual, recurrent, and metastatic hemangiopericytomas.

Multi-Disciplinary Approach to Skull Base Paragangliomas.

The treatment of skull base paragangliomas has moved towards the use of cranial nerve preservation strategies, using radiation therapy and subtotal resection in instances when aiming for gross total resection would be expected to cause increased morbidity compared to the natural history of the tumor itself. The goal of this study was to analyze the role of surgery in patients with skull base paragangliomas treated with CyberKnife stereotactic radiosurgery (SRS) for definitive tumor control. A retrospective review identified 22 patients (median age 65.5 years, 50% female) treated with SRS from 2010-2022. Fourteen patients (63.6%) underwent microsurgical resection. Gross total resection was performed in four patients for tympanic paraganglioma (n = 2), contralateral paraganglioma (n = 1), and intracranial tumor with multiple cranial neuropathies (n = 1). Partial/subtotal resection was performed for the treatment of pulsatile tinnitus and conductive hearing loss (n = 6), chronic otitis and otorrhea (n = 2), intracranial extension (n = 1), or episodic vertigo due to perilymphatic fistula (n = 1). Eighteen patients had clinical and imaging follow-up for a mean (SD) of 4.5 (3.4) years after SRS, with all patients having clinical and radiological tumor control and no mortalities. Surgery remains an important component in the multidisciplinary treatment of skull base paraganglioma when considering other outcomes besides local tumor control.

Stereotactic Radiosurgery for Cranial and Spinal Hemangioblastomas: A Single-Institution Retrospective Series.

Stereotactic radiosurgery (SRS) has been an attractive treatment modality for both cranial and spinal hemangioblastomas, especially for multiple lesions commonly associated with von Hippel-Lindau (VHL) disease. This study aims to provide the largest long-term analysis of treatment efficacy and adverse effects of SRS for cranial and spinal hemangioblastomas at a single institution. We evaluated the clinical and radiological outcomes of patients with hemangioblastomas treated with CyberKnife SRS at our institute from 1998 to 2022. The follow-up data were available for 135 hemangioblastomas in 35 patients. Twenty-eight patients had 123 hemangioblastomas associated with VHL, and 7 had 12 sporadic hemangioblastomas. The median age was 36 years, and the median tumor volume accounted for 0.4 cc. The SRS was administered with the median single-fraction equivalent dose of 18 Gy to the 77% median isodose line. At a median follow-up of 57 months (range: 3-260), only 20 (16.2%) of the VHL-associated and 1 (8.3%) sporadic hemangioblastomas progressed. The 5-year local tumor control rate was 91.3% for all hemangioblastomas, 91.7% among the sporadic lesions, and 92.9% in patients with VHL. SRS improved tumor-associated symptoms of 98 (74.8%) of 131 symptomatic hemangioblastomas, including headache, neck pain, dizziness, visual disturbances, dysesthesia, ataxia, motor impairment, seizures, and dysphagia. Two patients developed radiation necrosis (5.7%), and 1 of them required surgical resection. SRS is a safe and effective treatment option for patients with hemangioblastomas in critical locations, such as the brainstem, cervicomedullary junction, and spinal cord, and in patients with multiple hemangioblastomas associated with VHL disease.

SAT627 Is Cyberknife Stereotactic Radiosurgery Effective For Treating Cushing’s Disease?

Abstract Disclosure: G. Wintermyer: None. E. Villanueva: None. Patients with pituitary adenoma can often present with endocrine abnormalities. Transsphenoidal surgery(TSS) is the “gold standard” treatment. In patients with recurrent or post-surgery remaining adenoma, stereotactic radiosurgery with CyberKnife (CKRS) has demonstrated to be a good adjuvant therapy. Occasionally patients develop hypopituitarism and adrenal insufficiency (AI) post CKRS. Here is a patient with ACTH-secreting pituitary adenoma with Cushing’s disease who developed remission afterCKRS:52-year-old-male with PMHx of T2DM, hypothyroidism, HTN presented to hospital complaining of fatigue, ataxia, 40-lbs weight loss over four months and mood changes. Due to ataxia, CT of the head was done which revealed an Empty Sella. During the workup, ACTH and cortisol were detected 131 pg/mL and 37.5 ug/dL respectively. After ruling out life-threatening medical conditions, he was discharged with endocrinology referral for Empty Sella syndrome (ESS) and elevated ACTH. During endocrinology evaluation, patient was sent for testosterone, LH, FSH, ACTH, AM cortisol, prolactin and DHEAS tests. Results were as follows: elevated ACTH (91 pg/mL) and Cortisol (33.5ug/dL), elevated DHEAS (401 ug/dL) and prolactin (15 NG/dL), low testosterone (72 NG/dL), within appropriately low LH and FSH. Later, PM Salivary cortisol level, Dexamethasone suppression test(DST), and urine free cortisol (UFC) level were tested. He had pituitary MRI concurrently. Salivary cortisol and UFC were high. There was no suppression of cortisol level after DST. Pituitary MRI demonstrated pituitary tumor. He was diagnosed with Cushing’s disease and was referred to neurosurgery for pituitary tumor TSS. Patient was started on Ketoconazole prior to surgery. Pathology confirmed ACTH-secreting pituitary adenoma. After surgery, Cortisol level normalized, and the patient regained his energy. Post-surgery MRI showed complete resection of adenoma. Ketoconazole was discontinued post-operatively. Two years later, during routine workup, there were elevations in 24-hour and PM salivary cortisol levels. The patient was asymptomatic. He failed his DST. Repeat pituitary MRI showed small hypo enhancement at the bottom of Sella suspicious for pituitary adenoma recurrence. The patient underwent CKRS. Cortisol level and pituitary axis activity remained normal since CKRS. No change was noted in the six-month and one-year surveillance MRI. Even though TSS is a “gold standard” treatment for pituitary adenoma, the likelihood of remaining residues or recurrence of the tumor is high. Frequent pituitary hormone checks can detect recurrence of adenoma before emerging symptoms. CKRS should be considered as a therapeutic option for recurrent adenoma. Clinicians should frequently check patients for hypopituitarism and AI post-CKRS. Clinicians should also recognize that ESS may contribute to MRI-negative Cushing’s disease. Presentation: Saturday, June 17, 2023

A Pilot Study of an Interactive Virtual Tour Tool for Patient Education Prior to Undergoing High-Dose Rate Brachytherapy for Prostate Cancer.

High-dose rate (HDR) brachytherapy for treatment of prostate cancer is an invasive procedure that can be associated with patient anxiety. Patient education regarding the procedure can allow for better informed decision-making while also decreasing anxiety. We sought to develop and assess the utility of an interactive virtual tour tool that portrays a 360-degree view of the HDR brachytherapy patient experience, with the goals of providing patient education, decreasing patient anxiety, and assisting in wayfinding on the procedure day. Using a 360-degree camera, we captured multiple photographs that depicted the various hospital locations that a patient would navigate through on the day of their HDR brachytherapy procedure, including the medical center lobby, pre-operative/post-operative units, and the brachytherapy suite. We then compiled these 360-degree photographs using virtual tour software, to allow users to navigate throughout the locations. We added informational text, spoken audio, and videos associated with key staff, objects, and the brachytherapy procedure that allow the users to interact with and learn about these various components within the virtual tour. This tool was accessible via a website link on a computer, tablet, or smartphone and was provided at the time of consult to patients who were planning to undergo HDR brachytherapy for prostate cancer. A questionnaire assessing the tool's ease of use, educational value, wayfinding utility, and ability to improve anxiety and treatment decision-making was conducted prior to and after their procedure. Preliminary feedback from healthy volunteers is highly positive, with users finding that the tool is easily accessible, user-friendly, improves understanding of HDR brachytherapy, simulates the treatment experience accurately, helps with wayfinding, and has the potential to decrease patient anxiety and increase comfort with the treatment decision. Data from the patient questionnaires are being collected and will be analyzed. A 360-degree virtual tour tool allows for an easily accessible, immersive, and interactive method of patient education on an invasive, anxiety-associated procedure. This has the potential to decrease patient anxiety and improve comfort regarding treatment decision-making. This tool may be applied toward other relatively involved radiotherapy modalities, including gynecologic HDR brachytherapy, respiratory-gated treatments, and CyberKnife stereotactic radiosurgery.

Proton Based Stereotactic Radiotherapy for Skull Base Patients: Dosimetric Comparison to 4 Modern Radiation Treatment Modalities

Re-irradiation with ablative doses to a smaller target volume and strict critical structure constraint is a challenge for modern radiation planning and delivery systems. Several advanced radiation treatment techniques can be used for fractionated stereotactic ablative radiosurgery (FSRS) in select patients with unresectable recurrent head and neck tumors. In this study, in order to better understand the dosimetry advantage of each technique, we compare the stereotactic treatment plans of our new small spot size Hitachi proton treatment unit to those of CyberKnife stereotactic radiosurgery (CK), Gamma Knife radiosurgery (GK), volumetric modulated arc therapy (VMAT), and MR Linac radiotherapy (MRL). Ten FSRS skull base patients treated at our institution using VMAT (n = 5) or GK (n = 5) techniques. Intensity-modulated proton therapy (IMPT) plans were created in Raystation using Monte Carlo dose calculation algorithm. VMAT, CK, GK and MRL plans were generated in RayStation, Accuray Precision, Leksell Gamma Plan, and Monaco treatment planning systems, separately. Planning goals were to achieve the best target coverage of prescribed dose without compromising the critical organs at risk dose volume constraints of the clinical treatment plans. Plans were compared based on percent CTV coverage, Paddick conformity index (PCI), gradient index (GI, V50/V100), dose homogeneity index (HI, (D2-D98)/D50), low dose bath volume (LDBV, ratio of total volume irradiated between 20% and 50% prescription dose and the target volume), beam-on-time (BOT), and mean/maximum doses to brainstems. The median target volume was 15.5 cm3 (range 1.0 - 36.23 cm3). The prescription was 45 Gy in 5 fractions for VMAT patients, and 21 - 27 Gy in 3 fractions for GK patients. The comparison of the treatment plans of these 5 delivery modalities was shown in table. All techniques achieved comparable CTV coverage. GI was superior for GK plans and outstanding in CK and IMPT plans. IMPT plans were also outstanding in regard to BOT and PCI. Significantly improved HI, LDBV and brainstem mean doses were achieved in IMPT plans. For adjacent brainstem and other OARs, maximum doses were comparable among all techniques. In these five advanced radiation therapy modalities, proton therapy SBRT showed dosimetric advantage over other modalities to spare nearby OARs without sacrifice of target coverage. Further studies are needed to utilize this clinical benefit and investigate plan robustness.

Practical Guideline for Prevention of Patchy Hair Loss following CyberKnife Stereotactic Radiosurgery for Calvarial or Scalp Tumors: Retrospective Analysis of a Single Institution Experience

Introduction: Patchy alopecia is a common adverse effect of stereotactic radiosurgery (SRS) on the calvarium and/or scalp, yet no guidelines exist for its prevention. This study aims to investigate the incidence and outcomes of patchy alopecia following SRS for patients with calvarial or scalp lesions and establish preventive guidelines. Methods: The study included 20 patients who underwent CyberKnife SRS for calvarial or scalp lesions, resulting in a total of 30 treated lesions. SRS was administered as a single fraction for 8 lesions and hypofractionated for 22 lesions. The median SRS target volume was 9.85 cc (range: 0.81–110.7 cc), and the median prescription dose was 27 Gy (range: 16–40 Gy), delivered in 1–5 fractions (median: 3). The median follow-up was 15 months. Results: Among the 30 treated lesions, 11 led to patchy alopecia, while 19 did not. All cases of alopecia resolved within 12 months, and no patients experienced other adverse radiation effects. Lesions resulting in alopecia exhibited significantly higher biologically effective dose (BED) and single-fraction equivalent dose (SFED) on the overlying scalp compared to those without alopecia. Patients with BED and SFED exceeding 60 Gy and 20 Gy, respectively, were 9.3 times more likely to experience patchy alopecia than those with lower doses. The 1-year local tumor control rate for the treated lesions was 93.3%. Chemotherapy was administered for 26 lesions, with 11 lesions receiving radiosensitizing agents. However, no statistically significant difference was found. Conclusion: In summary, SRS is a safe and effective treatment for patients with calvarial/scalp masses regarding patchy alopecia near the treated area. Limiting the BED under 60 Gy and SFED under 20 Gy for the overlying scalp can help prevent patchy alopecia during SRS treatment of the calvarial/scalp mass. Clinicians can use this information to inform patients about the risk of alopecia and the contributing factors.

P11.50.A STEREOTACTIC RADIOSURGERY FOR RECURRENT MEDULLOBLASTOMA IN PEDIATRIC AND ADULT PATIENTS: A SINGLE-INSTITUTION EXPERIENCE

Abstract BACKGROUND Medulloblastoma is the most common malignant brain tumor in children. In recent decades, the therapeutic landscape has undergone significant changes, with stereotactic radiosurgery (SRS) emerging as a promising modality for the treatment of recurrent medulloblastoma. Our study aims to provide a comprehensive long-term analysis of the efficacy and safety of SRS for both pediatric and adult patients with recurrent medulloblastomas at a single institution. MATERIAL AND METHODS In our study, we retrospectively reviewed the clinical and radiological records of patients who underwent CyberKnife SRS for medulloblastoma at our institution between 1998 and 2023. Clinical and radiographic follow-up data were available for a total of 15 medulloblastomas in 10 patients. The study population consisted of 8 pediatric patients (ages 3-18) and 2 adult patients (ages 19-75). The median age at the time of SRS was 13 years and the median tumor volume accounted for 1.88 cc. The median biologically equivalent dose (BED) and single-fraction equivalent dose (SFED) were 126 Gy and 18 Gy, respectively. The SRS was administered at the 75% of the median isodose line. RESULTS Following a median follow-up of 39 months (range: 6-78) post-treatment, 8 (53.3%) of the medulloblastomas progressed, 2 (13.3%) showed radiographic regression, and 5 (33.3%) remained stable in volume. The 3-year local tumor control rate for all medulloblastomas was 65.2%, with lower rates observed in the adult cohort (50%) and higher rates in pediatric patients (67.3%). The 3-year overall survival rate was 70%, with significantly higher rates in pediatric patients (75%) compared to adult patients (50%). The 3-year progression-free survival rate was 58.3%, with higher rates in pediatric patients (60%) compared to adult patients (50%). Two pediatric patients developed radiation-induced edema, while two adult patients experienced radiation necrosis at the latest follow-up, with both adult patients passing away. CONCLUSION SRS is a safe and effective long-term treatment option for recurrent medulloblastoma in both pediatric and adult patients, resulting in improved patient outcomes. Although rare, radiation-induced edema and necrosis were observed as adverse events but were manageable. Overall, our findings provide optimistic evidence for the use of SRS as a viable treatment modality for medulloblastoma.

P11.48.A STEREOTACTIC RADIOSURGERY FOR EPENDYMOMA IN PEDIATRIC AND ADULT PATIENTS: A SINGLE-INSTITUTION EXPERIENCE

Abstract BACKGROUND Ependymoma is typically classified as WHO grade 2 and its anaplastic variant as grade 3. Despite standard treatment approaches, incomplete resection or anaplastic features can lead to poor prognosis. Stereotactic radiosurgery (SRS) is a promising minimally invasive option for recurrent ependymomas after surgery and radiation therapy. This study aims to evaluate the efficacy and safety of CyberKnife radiosurgery in treatment of WHO grade II versus III ependymomas in both pediatric and adult populations. MATERIAL AND METHODS In our study, we evaluated the clinical and radiological records of patients who underwent CyberKnife SRS for ependymoma at our institution between 1998 and 2023. The follow-up data were available for a total of 75 ependymomas in 34 patients. The study population consisted of 14 pediatric patients (ages 3-18) and 20 adult patients (ages 19-75). The median age was 21 years and the median tumor volume accounted for 0.64 cc. The median biologically equivalent dose (BED) and single-fraction equivalent dose (SFED) were 108 Gy and 16.6 Gy, respectively. The SRS was administered at the 77% of the median isodose line. RESULTS At a median follow-up of 42.7 months (range: 3.8-438.3) after treatment, our analysis revealed that only 17 (22.7%) ependymomas progressed. The 5-year local tumor control (5-yrs-LTC) rate for all ependymomas was 78.1%, with a lower rate of 59.6% observed in the pediatric cohort and a higher rate of 90.2% in adult patients. For ependymomas classified as WHO grade II, the 5-yrs-LTC rate was 85.9%, whereas it was 58.5% for those classified as WHO grade III. The 5-year overall survival (5-yrs-OS) rate was 73.6% for all patients, with significantly higher rates observed in pediatric patients (94.7%) than in adult patients (41%). The 5-yrs-OS rate was 100% for patients with WHO grade II tumors, whereas it decreased significantly to 35.9% for patients with WHO grade III ependymomas. The 5-year progression-free survival (5-yrs-PFS) rate was 68.5% for all patients, with higher rates observed in pediatric patients (78.3%) than in adult patients (49.2%). The 5-yrs-PFS rate for patients with WHO grade II lesions was 88.8%, whereas it was significantly lower at 32.6% for patients with WHO grade III tumors. Stereotactic radiosurgery (SRS) was effective in improving tumor-associated symptoms in 29 (85.3%) patients with 62 (82.7%) symptomatic ependymomas. These symptoms included headache, back pain, dizziness, nausea, vomiting, cranial nerve palsy, ataxia, motor impairment, sensory deficit, seizures, and weight loss. Notably, no patients developed adverse radiation effects. CONCLUSION CyberKnife SRS is a safe and effective treatment for ependymoma in both adults and children, with potential for significant improvements in tumor-related symptoms. Our study supports its use as a minimally invasive alternative to surgery, warranting further investigation.