Surgically targeted radiation therapy (STaRT) for recurrent brain metastases: Initial clinical experience.

PURPOSE: This study evaluates the outcomes of recurrent brain metastasis treated with resection and brachytherapy using a novel Cesium-131 carrier, termed surgically targeted radiation therapy (STaRT), and compares them to the first course of external beam radiotherapy (EBRT). METHODS: Consecutive patients who underwent STaRT between August 2020 and June 2022 were included. All patients underwent maximal safe resection with pathologic confirmation of viable disease prior to STaRT to 60 Gy to a 5-mm depth from the surface of the resection cavity. Complications were assessed using CTCAE version 5.0. RESULTS: Ten patients with 12 recurrent brain metastases after EBRT (median 15.5 months, range: 4.9-44.7) met the inclusion criteria. The median BED10Gy90% and 95% were 132.2 Gy (113.9-265.1 Gy) and 116.0 Gy (96.8-250.6 Gy), respectively. The median maximum point dose BED10Gy for the target was 1076.0 Gy (range: 120.7-1478.3 Gy). The 6-month and 1-year local control rates were 66.7% and 33.3% for the prior EBRT course; these rates were 100% and 100% for STaRT, respectively (p < 0.001). At a median follow-up of 14.5 months, there was one instance of grade two radiation necrosis. Surgery-attributed complications were observed in two patients including pseudomeningocele and minor headache. CONCLUSIONS: STaRT with Cs-131 presents an alternative approach for operable recurrent brain metastases and was associated with superior local control than the first course of EBRT in this series. Our initial clinical experience shows that STaRT is associated with a high local control rate, modest surgical complication rate, and low radiation necrosis risk in the reirradiation setting.

A study on inter-planner plan quality variability using a manual planning- or Lightning dose optimizer-approach for single brain lesions treated with the Gamma Knife® Icon™.

PURPOSE: The purpose of this study is to investigate inter-planner plan quality variability using a manual forward planning (MFP)- or fast inverse planning (FIP, Lightning)-approach for single brain lesions treated with the Gamma Knife® (GK) Icon™. METHODS: Thirty patients who were previously treated with GK stereotactic radiosurgery or radiotherapy were selected and divided into three groups (post-operative resection cavity, intact brain metastasis, and vestibular schwannoma [10 patients per group]). Clinical plans for the 30 patients were generated by multiple planners using FIP only (1), a combination of FIP and MFP (12), and MFP only (17). Three planners (Senior, Junior, and Novice) with varying experience levels re-planned the 30 patients using MFP and FIP (two plans per patient) with planning time limit of 60 min. Statistical analysis was performed to compare plan quality metrics (Paddick conformity index, gradient index, number of shots, prescription isodose line, target coverage, beam-on-time (BOT), and organs-at-risk doses) of MFP or FIP plans among three planners and to compare plan quality metrics between each planner's MFP/FIP plans and clinical plans. Variability in FIP parameter settings (BOT, low dose, and target max dose) and in planning time among the planners was also evaluated. RESULTS: Variations in plan quality metrics of FIP plans among three planners were smaller than those of MFP plans for all three groups. Junior's MFP plans were the most comparable to the clinical plans, whereas Senior's and Novice's MFP plans were superior and inferior, respectively. All three planners' FIP plans were comparable or superior to the clinical plans. Differences in FIP parameter settings among the planners were observed. Planning time was shorter and variations in planning time among the planners were smaller for FIP plans in all three groups. CONCLUSIONS: The FIP approach is less planner dependent and more time-honored than the MFP approach.

Implementation of superficial radiation therapy (SRT) using SRT-100 Vision™ for non-melanoma skin cancer in a Radiation Oncology clinic.

PURPOSE: This article describes our experience in implementation of superficial radiation therapy (SRT) using SRT-100 Vision™ for non-melanoma skin cancer. METHODS: Following the American Association of Physicists in Medicine Task Group-61 protocol, absolute output (absorbed dose to water at surface (cGy/min)) was measured for three energies (50, 70, and 100 kV) and for six applicators (1.5-5.0 cm in diameter). Percent depth dose (PDD) and profiles were also measured. Timer testing and ultrasound testing were performed. A treatment time calculation worksheet was created. Quality assurance (QA) of SRT-100 Vision was implemented. After treatment workflow for our clinic was developed, end-to-end (E2E) testing was performed using a Rando phantom. Considerations for treatment using SRT-100 Vision were made. RESULTS: Absolute output (cGy/min) decreases as energy increases and applicator size decreases. Due to scatter from the applicator, PDD at depths ≤5 mm does not follow conventional trends but PDD at depths ≥15 mm increases with increasing applicator size. Profiles for the 5 cm applicator do not have strong dependence on depth except profiles at 5 mm for 50 kV. Timer/end errors are negligible for all three energies. Ultrasound images confirm allowed field of view and depth as well as no image artifacts and spatial integrity. Daily, monthly and annual QA of SRT-100 Vision implemented in our clinic is listed in a table format. E2E testing results (<1%) demonstrate the functionality and performance of our treatment workflow. Our considerations for SRT treatment include patient, applicator size and energy selections, patient setup, and shields. CONCLUSIONS: This article is expected to serve as guidance for Radiation Oncology and/or Dermatology clinics aspiring to initiate an SRT program in their clinics.

Commissioning and comprehensive evaluation of the ArcCHECK cylindrical diode array for VMAT pretreatment delivery QA.

We present commissioning and comprehensive evaluation for ArcCHECK as a QA equipment for volumetric-modulated arc therapy (VMAT), using the 6 MV photon beam with and without the flattening filter, and the SNC patient software (version 6.2). In addition to commissioning involving absolute dose calibration, array calibration, and PMMA density verification, ArcCHECK was evaluated for its response dependency on linac dose rate, instantaneous dose rate, radiation field size, beam angle, and couch insertion. Scatter dose characterization, consistency and symmetry of response, and dosimetry accuracy evaluation for fixed aperture arcs and clinical VMAT patient plans were also investigated. All the evaluation tests were performed with the central plug inserted and the homogeneous PMMA density value. Results of gamma analysis demonstrated an overall agreement between ArcCHECK-measured and TPS-calculated reference doses. The diode based field size dependency was found to be within 0.5% of the reference. The dose rate-based dependency was well within 1% of the TPS reference, and the angular dependency was found to be ± 3% of the reference, as tested for BEV angles, for both beams. Dosimetry of fixed arcs, using both narrow and wide field widths, resulted in clinically acceptable global gamma passing rates on the 3%/3mm level and 10% threshold. Dosimetry of narrow arcs showed an improvement over published literature. The clinical VMAT cases demonstrated high level of dosimetry accuracy in gamma passing rates.