Radiosurgery Research Articles

RADT-25. IMPACT OF SAME-DAY MASK CREATION ON GAMMA KNIFE TREATMENT

Abstract OBJECTIVE Technological advances have allowed stereotactic radiosurgery (SRS) to be administered using fixation with a noninvasive mask, rather than with a stereotactic frame. While the use of such masks offers advantages including the ability to hypofractionate SRS and improved patient comfort, there has been criticism that it eliminates the possibility of same-day, “wheels in to wheels out” SRS. Our study examines the feasibility of conducting mask fitting and SRS treatment on the same day versus the conventional different-day approach. METHODS Eligible participants had either underwent single-fraction-SRS (SF-SRS) or were in their initial session of hypofractionated-SRS (HF-SRS). 100 patients who underwent SRS from September 2020 to June 2021 were assessed. 52 patients underwent same-day fabrication and treatment, and 48 patients received treatment at least one day following mask fabrication. The Leksell Gamma Knife (LGK) console data was processed, and operator reports from each patient were extracted and analyzed. RESULTS The average number of pauses, pause time, and number of gates was greater for same-day patients. There was no significant difference in the number of positioning alarms between the groups. There were no significant differences in percent overestimation of treatment time or number of treatment alarms. Treatment gates occurred on average 19 minutes earlier for same-day patients then different-day patients, which likely corresponds to “mask fatigue,” due to spending 20 minutes longer on the treatment table, while the masks are being fabricated. CONCLUSION Mask-based SRS can be done safely and efficiently in a single day, mirroring the approach of frame-based treatments.

RADT-43. RADIOSURGERY FOR BRAIN METASTASES FROM GYNECOLOGICAL PRIMARIES: AN INSTITUTIONAL PERSPECTIVE OF 58 METASTATIC LESIONS

Abstract Stereotactic radiosurgery (SRS) is being increasingly employed in the treatment of brain metastases. The evidence of radiological response of metastatic lesions from gynecological primary is lacking in literature. To assess the response rate of metastatic lesions to gamma knife SRS over a longitudinal follow-up period, a single centre prospectively maintained database was analysed retrospectively from 2014 to 2024. Lesion volumes were contoured at each follow up scan using Leksell Gammaplan software. Response assessment in neuro-oncology (RANO) criteria was used to assess radiological tumor response rates. Fifteen patients with 58 lesions were included. Average duration of radiological follow-up available was 16.7 months. The primary gynecological source of brain metastases in patients were cervical(n=4), ovarian(n=7), endometrial(n=3) and vulvar (n=1). Single fraction SRS was used for 49 lesions (range 16-20 Gy) and hypofractionated SRS for 9 lesions (8Gy x 3 to 9Gy x3). Average time to complete response was 9.01 months (range 1-25.7). The average follow-up for lesions with partial response was 12.2 months (range 1 -32) As per RANO criteria, complete response was seen in 33(56.9%) lesions and partial response in 25(43.1%). At 6month follow up, complete response was seen in 58.49% (n=31) of the lesions available(n=53) for assessment and partial response in 41.51%(n=22). At 18-months, complete response was seen in 66.67%(n=22) and partial response in 33.33%(n=11). Within pathological subgroups, endometrial (60%,n=3) primary showed higher rate of complete response at 6months than ovarian (52.7%,n=19), vulvar (50%, n=1) and cervical (40%,n=6) subgroups. Brain metastases from ovarian primary source were most encountered and endometrial metastases showed highest response rates to SRS. Six month and 18-month response rates were better than previously reported literature.

EXTH-81. A RARE CASE OF RELENTLESSLY PROGRESSIVE METASTATIC PINEOCYTOMA MANAGED WITH SEQUENTIAL MULTIMODAL THERAPY

Abstract BACKGROUND Pineocytoma is a rare pineal parenchymal WHO grade 1 tumor, typically well-managed with surgical resection alone. With gross total resection (GTR), 91% 1-year and 84% 5-year survival rates have been reported. Recurrent pineocytoma is rare and optimal management in that setting is unknown, in part owing to the rarity of the condition. METHODS We report an atypical course of pineocytoma in a 58-year-old male involving metastatic disease. RESULTS A pineal mass was identified upon MRI of the brain obtained for vision changes. Patient underwent GTR, pathology was consistent with pineocytoma, WHO grade 1. Ki-67 labeling index was low at 1-2%. Despite low-grade pathology, two years later, surveillance imaging demonstrated recurrence in the pineal region and a second lesion in the right thalamus. The patient underwent gamma knife surgery (GKRS) to both lesions. Three years later, he developed three new lesions in the right cerebellum and again underwent GKRS. Subsequent surveillance imaging identified new lesions in the right cerebellum and along ventricular walls, treated with further GKRS. Nine years after initial diagnosis, focal nodular leptomeningeal metastases were discovered, along with progression at the primary tumor site. Patient was treated with GKRS to the nodular deposits followed by pembrolizumab. Further disease progression as noted despite immunotherapy. Patient was treated with 6 cycles of temozolomide chemotherapy and at further progression 3 cycles of lomustine. Upon additional progression, further radiation therapy was administered with bevacizumab to reduce risk of radiation necrosis. Patient remains on surveillance 13 years after initial diagnosis with visual changes and mild headache representing only clinical issues. CONCLUSIONS Although exceedingly rare, pineocytoma is capable of metastasizing to brain parenchyma and the leptomeninges, as demonstrated in our patient. However, our case demonstrates prolonged survival is possible even in the setting of relentlessly progressive metastatic disease with utilization of multimodality treatment.

SURG-16. MULTIDISCIPLINARY TREATMENT OF HEMANGIOBLASTOMAS IN CENTRAL NERVOUS SYSTEM AND FUTURE PROSPECTS

Abstract Hemangioblastomas (HB) in central nervous system are originally benign tumors. However, they are extremely vascular and appropriate treatment of the feeders and drainers is important when performing HB resection. Approximately 20% of HB cases are thought to be caused by von Hippel-Lindau (VHL) disease. Patients with VHL disease often develop multiple HBs, and it may be difficult to treat them with excision alone. Recently, belzutifan, a molecular targeted drug indicated for treating HB in VHL disease cases, was approved by FDA. In this presentation, we will provide an overview of the multidisciplinary treatment at our facility. METHOD At our facility, we performed 84 cases of excision surgery from 1996 to 2019, and analyzed the results of these treatments. A high-definition 3D fused image was created before surgery to identify the feeders and drainers. Tumor embolization was performed on the feeder, which was thought to be located deep within the surgical field. In addition, gamma knife treatment was performed as appropriate for HBs that did not undergo extirpation. RESULTS The breakdown of cases was 46 with VHL disease and 38 with non-VHL disease. Postoperatively, KPS improved in 55% of cases, and some complications occurred in 18%. Gamma Knife treatment has been performed on 58 cases so far, and the 10-year tumor control rate is approximately 80%. DISCUSSION/SUMMARY This presentation revealed that multidisciplinary treatment is effective for HBs. In the future it is necessary to consider which HB cases belzutifan is useful for and how it should be combined with other treatments.

RBIO-03. A SMALL ANIMAL RADIATION RESEARCH PLATFORM (FLASH-SARRP) TO MEASURE IMMUNOLOGICAL EFFECT OF ULTRA HIGH DOSE RATE (FLASH) RADIOTHERAPY

Abstract Patients who undergo radiation therapy (RT), particularly fractionated courses, often develop lymphopenia. Clinical outcome for various cancer types, including brain tumors, identifies lymphopenia as a negative prognostic factor. The mechanism for RT induced lymphopenia is unclear. Simulated models suggest the volume of blood flowing through a radiation field could play a crucial role in death of radiosensitive lymphocytes. FLASH RT is ultrahigh dose rate administration of RT, >100 times faster dose rate than standard RT that has been observed to improve the therapeutic ratio in preclinical models by preferential normal tissue sparing. Hypothesized mechanisms include chemical reactions depleting oxygen in well oxygenated normal cells creating radioresistance, differing pro-inflammatory signaling impacting tumor and normal tissue, and less impact on circulating immune cells consequent to decreased proportion exposed during a treatment session which may enhance antineoplastic response. We designed the novel FLASH kV x-ray cabinet system for preclinical laboratory research (FLASH-SARRP) to deliver ultra-high dose rates up to 100 Gy/s as well as conventional dose rates of 1.0 Gy/s to facilitate comparative studies. A custom designed docking system was developed to reproducibly position and immobilize mouse for stereotactic radiation of the brain. Dose and dose rate measurements were performed with calibrated Gafchromic EBT3 film in solid water with 0.025 mm additional copper filter. FLASH-SARRP system delivered kV x-rays at an average dose-rate of 79.2±2.1Gy/s corresponding to 10 mm depth in the immobilized mouse brain. For the delivery of 15 Gy, treatment duration was 0.2 seconds for FLASH RT administration whereas it was 244 seconds for conventional dose rate. We successfully designed a high-precision platform to study partial brain x-ray FLASH effects in mice and studies are ongoing to assess differential impact on normal brain tissue, circulating cytokines, and immune cell populations for single dose and fractionated administration of FLASH and standard radiotherapy.

The role of local and systemic control methods in the treatment of oligometastatic breast cancer, taking into account biological subtypes (literature review)

Combined methods of treatment of oligometastatic breast cancer (OMBC) based on systemic drug treatment and local treatment methods - stereotactic radiation therapy (SRT) or surgical treatment - are not included in current clinical guidelines. The European Society of Medical Oncology (ESMO) recommends the use of local control methods for patients with breast cancer without taking into account the biological subtype of the tumor. This review presents a modern understanding of the oligometastatic biological subtype based on data from clinical studies on this topic, which could contribute to decision-making in real clinical practice.The aim of the review is analysis of the effectiveness of combined treatment methods: systemic drug therapy and local treatment methods (SRT) or surgical treatment of breast cancer of various molecular genetic subtypes.To assess the clinical effectiveness of various approaches to the treatment of breast cancer, depending on the biological subtype, a search was conducted for scientific publications in the Medline bibliographic database. Prospective and retrospective studies demonstrate an increase in the effectiveness of treatment through a combination of systemic therapy and local control methods (surgical treatment or SRT) OMBC depending on the biological subtypes. In hormonepositive breast cancer with bone damage, SRT is most preferable, whereas in visceral oligometastases, surgical treatment is recommended. For immunocompetent tumors of triple-negative and HER2-positive biological subtypes of breast cancer, surgical treatment of OMBC is not recommended, except in cases where the positive status of HER2 is combined with a high level of expression of hormonal receptors or metastatic bone damage.The results of current prospective studies focusing on certain biological subtypes of breast cancer will help further determine the role of this strategy in the treatment of this cohort of patients. Understanding the characteristics of the tumor process in breast cancer will allow you to personalize the treatment of patients with this disease.

Low‒Dose Cyclophosphamide Enhances the Tumoricidal Effects of 5-Day Spacing Stereotactic Ablative Radiotherapy by Boosting Antitumor Immunity.

To investigate the potential role of low‒dose cyclophosphamide (Cy) as a radiosensitizer by evaluating its impact on the immune response and the abscopal effect of stereotactic ablative radiotherapy (SABR) through preclinical models. CT26 tumors (immunologically hot) and 4T1 tumors (immunologically cold), grown in immunocompetent BALB/c and immunodeficient BALB/c‒nude mice, were irradiated with 20 Gy in two fractions with 5‒day spacing followed by intraperitoneal injections of 9 mg/kg Cy every 3 days. Immunological changes in CT26 tumors caused by the treatments were assessed using flow cytometry. Changes in the expression of HIF‒1α in tumors were also assessed. Splenocytes and bone marrow‒derived dendritic cells (DCs) were exposed to various concentrations of Cy to assess T cell proliferation and DC differentiation. The combination of Cy with RT (RT+Cy) significantly suppressed tumor growth compared to RT alone in immunocompetent mice, while that effect was not observed in immunodeficient mice. Additionally, RT+Cy effectively induced abscopal effects in hot and cold tumors, with increased CD8+ T cells in blood and tumors. Significantly higher expression levels of Granzyme B, IFN‒γ, and TNF‒α were observed in RT+Cy group compared to the RT alone group. In vitro data indicated that low‒dose Cy promotes DC differentiation. Low‒dose Cy suppressed the radiation‒induced upregulation of HIF‒1α in the tumors. Low‒dose Cy enhances tumoricidal effects of 5‒day spacing high‒dose RT by increasing anti-tumor immune responses.

Effectiveness of thalamotomy with Gamma Knife radiosurgery as a multitarget strategy in patients with complex trigeminal neuralgia

Effectiveness of thalamotomy with Gamma Knife radiosurgery as a multitarget strategy in patients with complex trigeminal neuralgia

Limitations of outcome prediction based on interfractional volume changes of large (≥ 10cm3) brain metastases during fractionated gamma knife radiosurgery.

This study investigated the interfractional volume changes of large (≥ 10 cm3) brain metastases (BMs) during fractionated gamma knife radiosurgery (FGKRS) to assess its predictive value for tumor control outcomes. The patients who underwent FGKRS for large BMs between January 2017 and December 2022 in our center were reviewed. The interfractional volume change was defined as the disparity in tumor volume (TV) measured between the magnetic resonance images acquired on the first treatment day and those obtained after 2 or 3 fractions during the course of FGKRS. A total of 73 lesions in 70 patients with various primary pathologies were included. Over a median follow-up period of 11months (range 1-77), the tumor control rate was 63%. Initial TV (cm3) was associated with progression free survival (PFS) and overall survival (OS) in both univariate and multivariate analyses (p = 0.01). Interfractional TV changes revealed an increase in 13 (17.8%) lesions, no change in 14 (19.2%) lesions, and a decrease in 46 (63.0%) lesions, with a mean volume reduction of 5% ± 0.12. Three cut-offs (5%, 10% and 15% volume decrement) were established and patients were divided into two groups based on each reference point. However, there were no significant differences in PFS and OS between the two groups, irrespective of the chosen cut-off value used. Interfractional volume changes of large BMs were not found to be associated with tumor control outcomes. Neither significant interfractional volume reduction nor significant volume increase necessarily predicts the tumor control, making early close monitoring essential after FGKRS.

Chronological characterization of hearing preservation after radiosurgery for vestibular schwannoma: a comprehensive meta-analysis.

Hearing outcomes following Gamma Knife radiosurgery (GKRS) for vestibular schwannoma (VS) are multifactorial and poorly characterized in prior literature. In this study the authors evaluated hearing outcomes chronologically to identify prognostic factors of serviceable hearing preservation (HP) rates following GKRS for VS. Six medical databases were queried according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Eligible studies reported VS treated with single-fraction GKRS and included the HP rate following GKRS. HP was defined as a postoperative Gardner-Robertson score ≤ 2 among patients with preoperative serviceable hearing. A meta-analysis with random-effects modeling was performed for variables of interest. Data from 42 articles with a total of 6582 patients were analyzed; the average age of patients was 54 years and the average follow-up time was 68 months. The pooled proportion of preoperative serviceable hearing was 76%, and the pooled HP rate was 60% at the last follow-up visit. At < 5 years after GKRS, age was significantly correlated with HP on both continuous and categorical analyses (p = 0.001 and p = 0.011, respectively). Between 5 and < 10 years of follow-up, HP was associated with a radiation dose of 12.5 Gy, but not with age or tumor volume. At ≥ 10 years after radiosurgery, a significant negative correlation was seen between marginal radiation dose and HP on both continuous and categorical analyses (p = 0.001 and p = 0.021, respectively). This meta-analysis identifies age and radiation dose as independent prognostic factors for HP. Age-related hearing deterioration appears to be concentrated in the first 5 years after GKRS, whereas radiation dose was associated with HP at last follow-up, between 5 and < 10 years, and at ≥ 10 years after radiosurgery. This meta-analysis offers an objective overview of the literature and a framework for clinical decision-making, with applications for treatment planning and patient counseling.

Stereotactic radiotherapy for patients with bone metastases: a selected group with low rate of radiation treatment during the last month of life?

BackgroundComplex high-precision radiotherapy, such as stereotactic body radiotherapy (SBRT), should only be offered to patients with sufficiently long survival. In the context of bone metastases radiotherapy, low rates of treatment close to the end of life, e.g. last 30 days (RT30), may serve as a quality of care indicator. While traditional, pain-relieving short-course regimens have been studied comprehensively, real-world SBRT results are still limited.MethodsRetrospective analysis (2010–2023, n = 1117 episodes) of patients with bone metastases treated with traditional single-fraction (8 Gy × 1) or multi-fraction regimens (often 4 Gy × 5 or 3 Gy × 10) compared to stereotactic single-fraction (12–16 Gy × 1) or multi-fraction regimens.ResultsExcept for gender, almost all baseline variables were uneven distributed. Failure to complete fractionated radiotherapy was uncommon in the stereotactic (4%) and non-stereotactic group (3%), p = 1.0. With regard to RT30, relevant differences emerged (19% for 8-Gy single-fraction versus 0% for stereotactic single-fraction, p = 0.01). The corresponding figures were 11% for multi-fraction non-stereotactic and 2% for multi-fraction stereotactic, p = 0.08. Median overall survival was shortest after 8-Gy single-fraction irradiation (4.2 months) and longest after stereotactic multi-fraction treatment (13.9 months). Neither stereotactic radiotherapy nor multi-fraction treatment improved survival in multivariate Cox regression analysis. Factors significantly associated with longer survival included better performance status, lower LabBM score (5 standard blood test results), stable disease outside of irradiated area(s), metachronous distant metastases, longer time interval from metastatic disease to bone irradiation, and outpatient status.ConclusionThe implementation of SBRT for selected patients has resulted in low rates of non-completion and RT30. Optimal selection criteria remain to be determined, but in current clinical practice we exclude patients with poor performance status, unfavorable blood test results (high LabBM score) and progressive disease sites not amenable to SBRT. Established, guideline-endorsed short-course regimens, especially 8-Gy single-fraction treatment, continue to represent an important palliative approach.

A Comparison of Stereotactic Radiation Therapy in Elderly Patients with Central or Peripheral Stage I-II (T1-3 N0 M0) Non-Small Cell Lung Cancer.

The objective of this study was to compare the clinical outcomes of stereotactic body radiation therapy (SBRT) in elderly patients aged 65 or older with clinical stage I-II non-small-cell lung cancer (NSCLC), specifically examining the differences between centrally located lung tumors and peripherally located lung tumors. From April 2009 to January 2020, a total of 136 patients with 136 tumors (65 central, 71 peripheral; NSCLC) at an early stage (T1-3N0M0) were treated with SBRT at a single institution. Central/peripheral location was assessed retrospectively on planning CT scans. A propensity score matching analysis was utilized to compare the two groups. In addition, the prognosis and related toxicity were compared between the two study arms. A total of 33 central tumors and 33 peripheral tumors were matched and analyzed. The results showed no significant differences in overall survival (OS) and progression-free survival (PFS) between the two groups. The 2-year OS was 71.88% (95% CI, 57.87%-89.27%) in the central lung cancer group, while it was 93.94% (95% CI, 86.14%-100.00%) in the peripheral lung cancer group (P=0.462). The 2-year PFS was 43.75% in the central lung cancer group, while it was 78.79% in the peripheral lung cancer group (P=0.279). Further subgroup analysis indicated that the location of peripheral tumor have a positive impact on OS in patients with adenocarcinoma. The occurrence of local failure, regional failure, or distant failure was comparable between central and peripheral tumors. There was no statistically significant difference in toxicity between the central and the peripheral tumor groups. The outcomes of SBRT for central tumors versus peripheral lung tumors in elderly patients with early-stage NSCLC were similar. SBRT demonstrated a similar level of safety in terms of toxicity for both central and peripheral lung tumors.

Current Radiotherapy Management of Extensive-Stage Small-Cell Lung Cancer in the Immunotherapy Era: An Italian National Survey on Behalf of the Italian Association of Radiotherapy and Clinical Oncology (AIRO)

Background: Extensive-stage small-cell lung cancer (ES-SCLC) treatment has recently been revolutionized by the advent of immune checkpoint inhibitors. This survey was conducted to evaluate the current pattern of care among Italian clinicians, in particular about the integration with radiation therapy (RT). Methods: In June 2023, 225 Italian cancer care professionals were invited to complete a 21-question web-based survey about ES-SCLC management through personal contacts and the Italian Association for Radiotherapy and Clinical Oncology (AIRO) network. Results: We received 90 responses; the majority were radiation oncologists (89%) with more than 10 years of experience (51%). The preferred management of ES-SCLC in patients with a good performance status was concomitant chemo-immunotherapy (84%). Almost all respondents recommended prophylactic cranial irradiation (PCI) (85%), taking into account age and thoracic response; PCI was performed mainly between the end of chemotherapy and before starting immunotherapy (37%), with a three-dimensional conformal technique (46%). Furthermore, 83% of respondents choose to deliver thoracic RT in the case of both an intrathoracic and extrathoracic response, with an RT schedule of 30 Gy/10 fractions. Stereotactic RT is increasingly being used in oligoprogressions. Conclusions: Our analysis showed the variability of real-world management of ES-SCLC. Future clinical trials and developments are needed to improve the multidisciplinary treatment of these patients.

Safety and Feasibility of Interventional Hybrid Fluoroscopy and Nuclear Imaging in the Work-up Procedure of Hepatic Radioembolization.

Purpose To evaluate the safety and feasibility of a novel hybrid nuclear and fluoroscopy C-arm scanner to be used during the work-up procedure of hepatic radioembolization. Materials and Methods In this prospective first-in-human clinical study, 12 participants (median age, 67 years [range: 37-78 years]; nine [75%] male, three [25%] female) with liver tumors undergoing work-up for yttrium 90 radioembolization were included (ClinicalTrials.gov NCT06013774). Work-up angiography and technetium 99m-macroaggregated albumin injection were performed in an angiography suite equipped with a hybrid C-arm that could simultaneously perform fluoroscopy and planar nuclear imaging. Technetium 99m-macroaggregated albumin was injected under real-time hybrid imaging, followed by in-room SPECT imaging. Safety and feasibility were studied by assessing adverse events, technical performance, additional x-ray radiation dose, and questionnaires completed by radiologists and technologists. Results No adverse events were attributed to the hybrid C-arm scanner. The additional x-ray radiation dose was low (median, 19 Gy · cm2; minimum: 12 Gy · cm2; maximum: 21 Gy · cm2 for participants who completed all imaging steps). The interventional personnel considered use of the hybrid C-arm scanner safe and feasible, although the additional time spent in the intervention room was considered long (median, 64 minutes; minimum: 55 minutes; maximum: 77 minutes for participants who completed all imaging steps). Conclusion Use of the hybrid C-arm scanner during the work-up procedure of hepatic radioembolization was found to be safe and feasible in this first-in-human clinical study. Keywords: Angiography, Fluoroscopy, Interventional-Vascular, Radionuclide Studies, Radiosurgery, Gamma Knife, Cyberknife, SPECT, Instrumentation, Physics, Technical Aspects, Technology Assessment Supplemental material is available for this article. Published under a CC BY 4.0 license. Clinical trial registration no. NCT06013774.

Ongoing prospective studies on reirradiation: A systematic review of a clinical trials database

IntroductionReirradiation has gained increasing interest, as advances in systemic therapy increase the survival of patients with cancer, and modern radiation techniques allow more precise treatments. However, high-quality prospective evidence on the safety and efficacy of reirradiation to guide clinical practice remains scarce. This systematic review evaluates ongoing prospective studies on reirradiation to identify research gaps and priorities. MethodsA systematic review of ClinicalTrials.gov was conducted on July 11, 2024, using search terms related to reirradiation. Inclusion criteria were prospective studies that were “recruiting,” “not yet recruiting,” or “active, not recruiting.” Studies with published results, retrospective, and in-silico studies were excluded. The review followed PRISMA 2020 guidelines and recommendations for systematic searches of clinical trial registries. ResultsAmong 1026 identified studies, 307 were screened, 99 were included. Fourty (40%) focused on central nervous system (CNS), 23 (23%) head and neck, and 17 (17%) on pelvic reirradiation. Most studies (90%) were interventional, with 32 (32%) phase II and 4 (4%) phase III trials. Sixteen trials were randomized (RCTs), including the 4 phase III trials for recurrent glioblastoma, rectal and nasopharyngeal cancer. Ten dose escalation trials focus on recurrent prostate, rectal, and non-small cell lung cancer as well as glioma. Modern high-precision radiotherapy techniques were frequently used, with 21 (21%) studies using stereotactic radiotherapy and 17 (17%) using particle therapy. Combinations with systemic therapies were investigated in 41 (41%) studies. ConclusionOngoing studies most frequently focus on CNS, head and neck, and pelvic reirradiation. There remains a critical need for RCTs, in particular for lung, breast, and gynecological cancers. Dose escalation trials, application of precision radiation techniques and combinations with modern systemic therapy may help define the optimal multimodality treatment schedules.

P188 Stereotactic MRI-guided adaptive radiotherapy for renal tumors in a solitary kidney

P188 Stereotactic MRI-guided adaptive radiotherapy for renal tumors in a solitary kidney

Exploratory Evaluation of Personalized Ultra-Fractionated Stereotactic Adaptive Radiotherapy (PULSAR) with CNS-Active Drugs in Brain Metastases Treatment

Exploratory Evaluation of Personalized Ultra-Fractionated Stereotactic Adaptive Radiotherapy (PULSAR) with CNS-Active Drugs in Brain Metastases Treatment

Financial Toxicity and Quality-of-Life Outcomes on a Phase 1 5-fraction Stereotactic Partial Breast Irradiation Protocol for Early-Stage Breast Cancer

Financial Toxicity and Quality-of-Life Outcomes on a Phase 1 5-fraction Stereotactic Partial Breast Irradiation Protocol for Early-Stage Breast Cancer

Minimum cochlear dose impacts hearing after radiosurgery for sporadic vestibular schwannoma.

It is uncertain which cochlear dose parameters significantly impact hearing after stereotactic radiosurgery (SRS) for sporadic vestibular schwannoma (VS). The objective of this study was to determine the impact of cochlear dose parameters on hearing outcomes for patients with serviceable hearing (SH). This was a historical cohort study performed at a single tertiary center that included patients with sporadic VS and SH who underwent single-session Gamma Knife radiosurgery treatment from 2007 to 2022. Associations of cochlear dose parameters with time to non-SH and rates of change in pure-tone average (PTA) and word recognition score (WRS) following SRS were assessed. A total of 205 patients with SH underwent SRS for a sporadic VS. At SRS, 54 (26%) tumors were confined to the internal auditory canal and 151 (74%) extended into the cerebellopontine angle. At 2, 5, and 10 years following SRS, 62%, 37%, and 15% of patients maintained SH, respectively. The median time to non-SH was 1.8 years. The median rates of change in PTA and WRS were 6.0 dB of hearing loss per year and -6.5% per year, respectively. In a multivariable analysis, each 1-Gy increase in minimum cochlear dose was significantly associated with time to non-SH (HR 1.5, 95% CI 1.2-1.9), rate of change in PTA decibel hearing loss per year (parameter estimate [PE] 3.4, 95% CI 0.6-6.2), and rate of change in WRS percentage per year (PE -6.4, 95% CI -11.2 to -1.5). The associations of each 1-Gy increase in mean cochlear dose with hearing outcomes were only significant among patients with class B hearing (time to non-SH HR 1.3, 95% CI 1.1-1.6; rate of change in PTA PE 3.6, 95% CI 1.2-5.9; and rate of change in WRS PE -5.7, 95% CI -9.7 to -1.7). The minimum cochlear dose impacts hearing outcomes after SRS for VS and should be considered in radiosurgical treatment planning. In this cohort, the mean cochlear dose was only associated with hearing outcomes in the subgroup of patients with class B hearing at SRS.

PSOR07 Presentation Time: 12:00 PM: Salvage Tumor-Targeted HDR Brachytherapy Boost to Stereotactic Radiotherapy: Early Experience

PSOR07 Presentation Time: 12:00 PM: Salvage Tumor-Targeted HDR Brachytherapy Boost to Stereotactic Radiotherapy: Early Experience