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Background: Gamma knife radiosurgery (GKRS) is often performed to treat brain metastases (BrMs). Widely referenced guidelines have suggested post-treatment imaging studies at 3-month intervals. However, clinicians frequently obtain magnetic resonance imaging (MRI) studies at <3 months after GKRS., Methods: We performed a retrospective medical record review study to assess the utility of early (<3 months) MRI after GKRS in patients with BrMs., Results: A total of 415 GKRS procedures were performed. For 325 patients, early MRI studies were obtained. A total of 31 patients had new or worsened neurological symptoms. The early MRI studies showed adverse findings in 25 patients (78%), which in 23 (72%) had resulted in a change in treatment. For 294 patients, no new or worsened neurological symptoms were found on early MRI studies. Of these 294 patients, 86 (29%) had ≥1 adverse finding on MRI, and 60 (20%) had a change in management as a result. However, no rapidly growing tumors or other emergent adverse findings were seen., Conclusions: Early MRI (within 3 months) after post GKRS will frequently show adverse findings even in asymptomatic patients, more often in patients aged <65 years and patients with multiple treated BrMs. However, according to the nature of the adverse findings observed in our retrospective study, it is unlikely that the clinical outcomes would have been affected if the post-GKRS MRI studies had been deferred to 3 months after treatment. Our data support deferring post-GKRS MRI to 3 months after treatment in the absence of new neurological signs or symptoms., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Objective: MRI provides clear visualization of spinal cord, tumor, and bone for patient positioning and verification during MRI-guided radiotherapy (MRI-RT). Therefore, we wished to evaluate spine stereotactic ablative radiotherapy (SABR) feasibility with MRI-RT. Given dosimetric limitations of first generation Co-60 MRI-RT, we then evaluated improvements by newer linear accelerator (linac) MRI-RT., Methods: Nine spinal metastases were treated with Co-60 MRI-RT. Seven received a single 16 Gy fraction, and two received three fractions totaling 24 or 30 Gy. After replanning with linac MRI-RT software, comparisons of organ at risk and dose spillage objectives between Co-60 and linac plans were performed., Results: Spinal cord and cauda equina dose constraints were met in all Co-60 cases. Treatments were delivered successfully with real-time imaging during treatment and no treatment-related toxicities. While limits for dose spillage into surrounding soft tissues were not achieved due to the limitations of the Co-60 system, this could be corrected with linac MRI-RT delivery., Conclusions: MRI-RT SABR of spinal metastases is feasible with Co-60 MRI-RT. Dose delivery is improved by linac MRI-RT., Advances in Knowledge: This is the first report of MRI-RT for SABR of spinal metastases. The enhanced visualization of anatomy by MRI may facilitate RT dose escalation for spine SABR.

Purpose/objective(s): Although patients with brain metastasis treated with stereotactic radiosurgery (SRS) in the definitive or post-operative setting have high rates of local control, surveillance imaging is necessary to assess for central nervous system (CNS) recurrence. Guidelines recommend magnetic resonance imaging (MRI) of the brain every three months for surveillance in asymptomatic patients post-SRS. However, optimal frequency and duration of surveillance imaging in long-term survivors is unknown. Our objective is to define the yield and cost of surveillance MRIs in long-term (> 1 year) survivors following SRS.Materials/methods: We identified a cohort of patients with brain metastases treated with SRS in the definitive or postoperative setting at a single institution from 8/2014 to 9/2019. Eligible patients had at least one-year of follow-up with absence of CNS disease failure up to and including the first MRI of the brain after 12 months from SRS. Each post-treatment MRI of the brain was assessed for disease progression or new lesions. CNS disease-free survival was time from SRS to last follow-up, death or CNS failure. Delay to diagnosis and cost per patient were estimated using hypothetical MRI schedules of 2, 3, 4 and 6 months from 1-year post-treatment while CNS disease-free. Delay to diagnosis was calculated as time from actual CNS progression to hypothetical imaging date. Medicare reimbursement median cost of $498 per MRI brain with and without contrast was used for this analysis.Results: A total of 373 patients treated with SRS for brain metastasis were identified at our institution. 61 patients met eligibility criteria for inclusion in this study (median follow-up 2.50 years, median age at treatment 60 years). The median CNS disease-free survival in this population was 2.37 years from date of SRS. 15 patients (24.6%) had CNS progression at median time of 2.26 years. Of the 15 patients, 3 patients were symptomatic at recurrence. Median frequency of MRI after one year post SRS was 5.9 months. Per patient, $1156 was spent annually on MRIs of the brain after 12 months with average annual yield of 17.0%. The cost per diagnosis of CNS progression was $6806. A 2-month, 3-month, 4-month and 6-month MRI schedule had a respective estimated delay to diagnosis of 0.69 months, 1.13 months, 1.44 months and 3.19 months. The respective mean total cost of each MRI schedule per patient from one-year post-treatment while CNS disease-free was $4662, $3053, $2229 and $1380.Conclusion: Patients with metastatic disease to the brain treated definitively or postoperatively with SRS without evidence of CNS recurrence at one year have a low rate of CNS failure and relatively good prognosis. Based strictly on limiting delay of diagnosis, a 2-month MRI Brain schedule is optimal in this population, albeit with a relatively small increase in financial cost over the patient's lifespan. We propose a multi-institutional study of long-term survivors with brain metastasis to strengthen these findings.Author Disclosure: B.J. Rich: None. D. Kwon: None. Y.S. Soni: None. D.L. John: None. J.B. Bell: None. G. Azzam: None. E.A. Mellon: None. R. Yechieli: Support and guide school in strategic and management related matters; Toras Chaim Toras Emes, Miami FL.C. Benjamin: None. R. Benveniste: None. R.J. Komotar: None. M. Ivan: None. J. Morcos: None. T. Diwanji: None. [ABSTRACT FROM AUTHOR]