Publications by authors named "Samuel Chao"

Objectives: This practice parameter was revised collaboratively by the American College of Radiology (ACR) and American Radium Society (ARS). Stereotactic body radiation therapy (SBRT) precisely delivers higher dose(s) of radiation in 5 of fewer fractions, compared with conventional radiation. Given the complexity and technical nature of this treatment technique, practice parameters are needed to provide guidance to physicians and physicists.

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Purpose: Single fraction preoperative stereotactic radiosurgery (SRS) has historically used a 10% to 20% dose reduction standard dosing. However, the effects of this dose reduction are not well characterized. The goal of this study was to compare outcomes and toxicity of standard dose (SD) with reduced dose (RD) single fraction preoperative SRS.

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Background: Secondary trigeminal neuralgia (TN) is often associated with benign meningiomas and schwannomas. For patients who are unable to undergo surgical resection, Gamma Knife radiosurgery (GKRS) is a well-established alternative for tumor control. There is limited data on the pain outcomes in these patients undergoing tumor-targeted GKRS.

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Purpose/objective: Radiation necrosis (RN) is a potential complication after stereotactic radiosurgery (SRS) for brain metastases. This study develops a recursive partitioning analysis (RPA) to identify patients at risk for RN following SRS.

Methods: Patients who underwent single-fraction SRS for intact brain metastases at a single institution from 2017 to 2021 were identified.

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Background: High-grade gliomas (HGG) are incurable primary brain tumors. Laser interstitial thermal therapy (LITT) has emerged as an alternative to surgery for select patients. Hyperthermia can improve the efficacy of radiation and chemotherapy.

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Purpose: Radiation necrosis (RN) is a dose-limiting toxicity of stereotactic radiosurgery (SRS) for brain metastases. Oral corticosteroids are not optimal for long-term management, given multiple side effects. Boswellia serrata (BS) is an over-the-counter supplement traditionally known for its anti-inflammatory properties and has recently been shown to reduce cerebral edema.

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Purpose: Vestibular schwannomas (VS) are the most common benign intracranial nerve sheath tumors. Surgery and radiation therapy - particularly stereotactic radiosurgery (SRS) - are the primary treatment options. SRS is the dominant treatment for small- and medium-sized VS and selected larger tumors due to its excellent local control rates and favorable safety profile compared with surgery.

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Background And Objective: Radiosurgery can serve as a primary, adjuvant, or salvage treatment modality for cavernous sinus tumors (CST), providing high tumor control. However, particularly with cavernous sinus expansion, there may be insufficient distance from the optic apparatus to perform radiosurgery safely. The internal carotid artery adjacent to the distal dural ring (ICAddr), when enhancing similarly to the CST, can be difficult to delineate, and can lead to over-contouring of target volume near the optic nerve and therefore increasing the risk of radiation-induced optic toxicity.

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Purpose: Meningiomas are the most common primary intracranial tumor. Somatostatin receptor 2 is almost universally expressed in meningioma tissue. For patients who require adjuvant radiation, somatostatin receptor based (68)Ga-DOTATATE positron emission tomography (PET) imaging can detect additional or residual disease not discernible on magnetic resonance imaging.

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The ARS brain committee recommends that vorasidenib may be appropriate for recurrent or residual IDH-mutant grade 2 oligodendroglioma or astrocytoma. Vorasidenib is usually not appropriate for completely resected grade 2 oligodendroglioma or astrocytoma, any grade 3 oligodendroglioma or astrocytoma, or combined with radiotherapy and/or chemotherapy for any grade 2-3 glioma.

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Article Synopsis
  • The study focuses on the effectiveness of adjuvant radiation therapy, specifically intensity-modulated radiation therapy (IMRT) and stereotactic radiosurgery (SRS), after subtotal resection of WHO grade II meningiomas due to the limited existing research.
  • A retrospective analysis of 39 patients revealed 3-, 5-, and 10-year progression-free survival rates of 81.1%, 61.2%, and 44.6%, respectively, demonstrating overall acceptable control rates.
  • No significant differences were found in progression-free survival or radiation necrosis occurrences between the IMRT and SRS groups, suggesting both treatments are similarly effective for managing residual tumors.
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Spine metastases (SMs) are common, arising in 70% of the cases of the most prevalent malignancies in males (prostate cancer) and females (breast cancer). Stereotactic body radiotherapy, or SBRT, has been incorporated into clinical treatment algorithms over the past decade. SBRT has shown promising rates of local control for oligometastatic spinal lesions with low radiation dose to adjacent critical tissues, particularly the spinal cord.

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Purpose: Spinal stereotactic body radiation therapy (SBRT) has become the standard of care in management of patients with limited sites of metastatic disease, radioresistant histologies, painful vertebral metastases with long life expectancy and cases of reirradiation. Our case-based guidelines aim to assist radiation oncologists in the appropriate utilization of SBRT for common, yet challenging, cases of spinal metastases.

Methods And Materials: Cases were selected to include scenarios of large volume sacral disease with nerve entrapment, medically inoperable disease abutting the thecal sac, and local failure after prior SBRT.

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Purpose: To compare plan quality among photon volumetric arc therapy (VMAT), Gamma Knife, and three different proton beam modalities.

Methods: Fifty-five brain lesions from 20 patients were planned with three different proton spot size ranges of cyclotron-generated proton beams, CPBs (spot size σ: 2.7-7.

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Purpose: Meningiomas represent the most common primary tumor of the central nervous system. Current treatment options include surgical resection with or without adjuvant radiation therapy (RT), definitive RT, and observation. However, the radiation dose, fractionation, and margins used to treat patients with WHO grade 2 meningiomas, which account for approximately 20% of all meningiomas, are not clearly defined, and deciding on the optimal treatment modality can be challenging owing to the lack of randomized data.

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Background And Objectives: We present our experience in the management of symptomatic vertebral hemangiomas with epidural extension (SVHEE) using spine stereotactic radiosurgery (SSRS).

Methods: An Institutional Review Board approved retrospective review of all SVHEE patients treated with SSRS at our institution (2007-2022) was performed. Baseline patient demographics, clinical presentation, lesion volume, and Bilsky grade (to directly evaluate the epidural component) were determined.

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Background: Single-session stereotactic radiosurgery (SRS) or surgical resection alone for brain metastases larger than 2 cm results in unsatisfactory local control. We conducted a phase I trial for brain metastases(>2 cm) to determine the safety of preoperative SRS at escalating doses.

Methods: Radiosurgery dose was escalated at 3 Gy increments for 3 cohorts based on maximum tumor dimension starting at: 18 Gy for >2-3 cm, 15 Gy for >3-4 cm, and 12 Gy for >4-6 cm.

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The American Radium Society (ARS) Central Nervous System (CNS) committee reviewed literature on epidermal growth factor receptor mutated (EGFRm) and ALK-fusion (ALK+) tyrosine kinase inhibitors (TKIs) for the treatment of brain metastases (BrMs) from non-small cell lung cancers (NSCLC) to generate appropriate use guidelines addressing use of TKIs in conjunction with or in lieu of radiotherapy (RT). The panel developed three key questions to guide systematic review: can radiotherapy be deferred in patients receiving EGFR or ALK TKIs at (1) diagnosis or (2) recurrence? Should TKI be administered concurrently with RT (3)? Two literature searches were performed (May 2019 and December 2023). The panel developed 8 model cases and voted on treatment options using a 9-point scale, with 1-3, 4-6 and 7-9 corresponding to usually not appropriate, may be appropriate, and usually appropriate (respectively), per the UCLA/RAND Appropriateness Method.

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Purpose: Primary treatment of spinal ependymomas involves surgical resection, however recurrence ranges between 50 and 70%. While the association of survival outcomes with lesion extent of resection (EOR) has been studied, existing analyses are limited by small samples and archaic data resulting in an inhomogeneous population. We investigated the relationship between EOR and survival outcomes, chiefly overall survival (OS) and progression-free survival (PFS), in a large contemporary cohort of spinal ependymoma patients.

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Radiation therapy with stereotactic radiosurgery (SRS) or whole brain radiation therapy is a mainstay of treatment for patients with brain metastases. The use of SRS in the management of brain metastases is becoming increasingly common and provides excellent local control. Cerebral radiation necrosis (RN) is a late complication of radiation treatment that can be seen months to years following treatment and is often indistinguishable from tumor progression on conventional imaging.

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Article Synopsis
  • The study focuses on improving the time-to-treatment initiation (TTI) for patients undergoing external beam radiotherapy through a standardized workflow.
  • Data from 2012-2019 showed a significant decrease in TTI across various treatment techniques (3D, IMRT, SBRT) after standardizing procedures.
  • The consistent monitoring of TTI helped maintain shorter treatment times over the years, enhancing the overall efficiency of the radiation oncology department.
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Purpose: Brain metastases are common among adult patients with solid malignancies and are increasingly being treated with stereotactic radiosurgery (SRS). As more patients with brain metastases are becoming eligible for SRS, there is a need for practical review of patient selection and treatment considerations.

Methods And Materials: Two patient cases were identified to use as the foundation for a discussion of a wide and representative range of management principles: (A) SRS alone for 5 to 15 lesions and (B) a large single metastasis to be treated with pre- or postoperative SRS.

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Background: This practice parameter was revised collaboratively by the American College of Radiology (ACR), and the American Radium Society. This practice parameter provides updated reference literature regarding radiation oncology practice and its key personnel.

Methods: This practice parameter was developed according to the process described under the heading The Process for Developing ACR Practice Parameters and Technical Standards on the ACR website ( https://www.

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Background And Objective: Malignant epidural spinal cord compression (MESCC), often presenting with back pain and motor/sensory deficits, is associated with poor survival, particularly when there is loss of ambulation. The purpose of this review is to evaluate the literature and discuss appropriate workup and management of MESCC, specifically in the emergent setting.

Methods: A PubMed search was conducted on "spinal cord compression" and "radiation therapy.

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