Evaluating Critical Brain Radiation Doses in the Treatment of Multiple Brain Lesions with Gamma Knife Radiosurgery

Background: Treatment of patients with multiple brain metastases has shifted to stereotactic radiosurgery, withholding whole-brain (WB) radiation therapy. However, radiation toxicity to the brain is a concern when treating multiple brain lesions with single-fraction stereotactic radiosurgery. Objective: The purpose of this study was to determine the changes in brain radiation doses when treating various numbers of targets and lesion volumes. Methods: We simulated different treatment plans with different combinations of varying tumor volumes including 0.1, 0.5, 1, 2, and 5 cm³, and tumor numbers including 1, 3, 5, 10, 15, 20, and 25. Treatment planning was performed for all combinations in a computerized tomography of the head of a patient, using Leksell GammaPlan version 10.1.1 (Elekta AB, Stockholm, Sweden). Two different dosing strategies were used. In the lower-prescription dosing schedule, a marginal dose was given to the 50% isodose line, and 20 Gy were used when the number of lesions was less than 15 and 18 Gy were applied when the number of lesions was equal to or more than 15. In the higher-prescription dosing schedule, a marginal dose of 24 Gy was used for lesions of less than 5 cm³ and 20 Gy were applied for lesions equal to 5cm³. The mean WB dose, the WB integral dose, and the volume of brain receiving 12 Gy (V12 Gy) were calculated for each scenario. Also, the beam-on time of the Gamma Knife 4C unit was reported for all treatment scenarios. Results: Regression analysis showed that the total tumor volume was a more significant predictor of V12 Gy than the number of lesions, and a linear correlation between the total tumor volume and V12 Gy was found. We also found that the total tumor volume was a more significant predictor of the mean WB dose and the WB integral dose compared to the number of lesions. Conclusion: Our results suggest that multiple small to mid-sized lesions could be safely treated with a single-fraction gamma knife.
Stereotact Funct Neurosurg 2017;95:268-278

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Comparative Evaluation of Magnetic Resonance-Guided Focused Ultrasound Surgery for Essential Tremor

Background: Treatment options for patients with drug-resistant essential tremor (ET) are limited. Magnetic resonance-guided focused ultrasound surgery (MRgFUS) is an emerging technique to treat refractory ET. Objectives: To present MRgFUS as an alternative to radiofrequency (RF) thalamotomy or deep brain stimulation (DBS) for ET treatment. Methods: We retrospectively analyzed 59 patients who underwent unilateral surgery for drug-resistant ET. Treatments included RF thalamotomy (n = 17), DBS (n = 19), and MRgFUS (n = 23). The outcomes measured were tremor severity and treatment-related complications. Results: At 1 month postoperatively, 100% of RF thalamotomy patients, 89.5% of DBS patients, and 91.3% of MRgFUS patients exhibited absent/mild tremor (successful treatment); other patients exhibited partial relief. At 12 months postoperatively, treatment success for each procedure was observed in 70.6, 84.2, and 78.3% of patients, respectively. At 1 month postoperatively, treatment-related complications had occurred in 58.8, 5.3, and 13.0% of patients, respectively. At 12 months postoperatively, side effects persisted in 11.8, 21.1, and 4.4% of patients, respectively. No statistical differences in treatment success were observed between treatments or over time. Complication rates differed between treatment modalities (p Conclusions: Patients with drug-resistant ET received equivalent results from RF thalamotomy, DBS, and MRgFUS. DBS and MRgFUS resulted in fewer treatment-related complications.
Stereotact Funct Neurosurg 2017;95:279-286

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Etiologies and management of cutaneous flushing

The second article in this 2-part continuing medical education series reviews the following malignant causes of flushing: mastocytosis, medullary thyroid carcinoma, pheochromocytoma, carcinoid tumors, gastroenteropancreatic neuroendocrine tumors, bronchogenic carcinoma, vasointestinal polypeptide secreting tumors, and renal cell carcinoma. The information provided will allow physicians to better distinguish patients who have worrisome presentations that require a more thorough investigation. Appropriate diagnostic workup and treatment options for these malignancies are reviewed.

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CME examination

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Etiologies and management of cutaneous flushing

The flushing phenomenon may represent a physiologic or a pathologic reaction. Although flushing is usually benign, it is prudent that the physician remains aware of potentially life-threatening conditions associated with cutaneous flushing. A thorough investigation should be performed if the flushing is atypical or not clearly associated with a benign underlying process. The diagnosis often relies on a pertinent history, review of systems, physical examination, and various laboratory and imaging modalities, all of which are discussed in the 2 articles in this continuing medical education series.

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Table of Contents

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Partial biopsies and persistent nevi: Communicate clearly and proceed with caution

To the Editor: We read the article by Hiscox et al1 with great interest. The authors identified 147 nevi with positive histologic margins and a diagnosis of moderate cytologic atypia (MDN). Only 6 recurred over an average interval of 624 days. The authors concluded that "given the low recurrence in our sample of MDN with nevus cells detectable at histologic margins, it seems appropriate to not re-excise these lesions."

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