Browsing by Author "Lim, Gerald"

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    A phase III, multicenter, randomized controlled trial of preoperative versus postoperative stereotactic radiosurgery for patients with surgically resectable brain metastases
    (2022-12-30) Das, Subhadip; Faruqi, Salman; Nordal, Robert; Starreveld, Yves; Kelly, John; Bowden, Gregory; Amanie, John; Fairchild, Alysa; Lim, Gerald; Loewen, Shaun; Rowe, Lindsay; Wallace, Carla; Ghosh, Sunita; Patel, Samir
    Abstract Background Postoperative stereotactic radiosurgery (SRS) is a standard management option for patients with resected brain metastases. Preoperative SRS may have certain advantages compared to postoperative SRS, including less uncertainty in delineation of the intact tumor compared to the postoperative resection cavity, reduced rate of leptomeningeal dissemination postoperatively, and a lower risk of radiation necrosis. The recently published ASCO-SNO-ASTRO consensus statement provides no recommendation for the preferred sequencing of radiotherapy and surgery for patients receiving both treatments for their brain metastases. Methods This multicenter, randomized controlled trial aims to recruit 88 patients with resectable brain metastases over an estimated three-year period. Patients with ten or fewer brain metastases with at least one resectable, fulfilling inclusion criteria will be randomized to postoperative SRS (standard arm) or preoperative SRS (investigational arm) in a 1:1 ratio. Randomization will be stratified by age (< 60 versus ≥60 years), histology (melanoma/renal cell carcinoma/sarcoma versus other), and number of metastases (one versus 2–10). In the standard arm, postoperative SRS will be delivered within 3 weeks of surgery, and all unresected metastases will receive primary SRS. In the investigational arm, enrolled patients will receive SRS of all brain metastases followed by surgery of resectable metastases within one week of SRS. In either arm, single fraction or hypofractionated SRS in three or five fractions is permitted. The primary endpoint is to assess local control at 12 months in both arms. Secondary endpoints include local control at other time points, regional/distant brain recurrence rates, leptomeningeal recurrence rates, overall survival, neurocognitive outcomes, and adverse radiation events including radiation necrosis rates in both arms. Discussion This trial addresses the unanswered question of the optimal sequencing of surgery and SRS in the management of patients with resectable brain metastases. No randomized data comparing preoperative and postoperative SRS for patients with brain metastases has been published to date. Trial registration Clinicaltrials.gov , NCT04474925; registered on July 17, 2020. Protocol version 1.0 (January 31, 2020). Sponsor: Alberta Health Services, Edmonton, Canada (Samir Patel, MD).
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    Dosimetric Consequences of Rotational Patient Setup Errors in Stereotactic Radiosurgery
    (2016) Briscoe, Michael; Ploquin, Nicolas; Voroney, Jon-Paul; Schinkel, Colleen; Spencer, David; Lim, Gerald
    The level of rotational patient setup error needed to impact stereotactic radiosurgery (SRS) treatments is not well defined. The purpose of this study was to explore potential rotational setup error thresholds for SRS treatments of brain metastases. The groups analyzed in this study consisted of either single isocentric targets or multiple nonisocentric targets. Rotations between 0.5° and 7° were simulated, and the percent of the target volume that received the prescription dose (Vp) was compared between the original plans and rotation simulations to determine what degree of rotations would cause notable Vp loss. The results suggest that a rotational patient setup error threshold of 2° around all axes for treatments of single isocentric targets is conservative. For treatments of multiple nonisocentric targets, especially those that are far from the treatment isocenter, the rotational setup error threshold may need to be as low as or lower than 0.5°.