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Objective: Esthesioneuroblastoma (ENB), also known as olfactory neuroblastoma, is a rare, malignant tumor of neuroectodermal origin that arises from the olfactory neuroepithelium. In this study the authors present the first series in the literature on distant brain metastases (BMs) secondary to ENB that were treated with stereotactic radiosurgery (SRS), to evaluate the safety and effectiveness of SRS for this indication., Methods: A retrospective analysis of clinical and radiological outcomes of patients with ENB who underwent CyberKnife (CK) SRS at a single center was conducted. The clinical and radiological outcomes of patients, including progression-free survival, overall survival, and local tumor control (LTC) were reported., Results: Between 2003 and 2022, 32 distant BMs in 8 patients were treated with CK SRS at Stanford University. The median patient age at BM diagnosis was 62 years (range 47-75 years). Among 32 lesions, 2 (6%) had previously been treated with surgery, whereas for all other lesions (30 [94%]), CK SRS was used as their primary treatment modality. The median target volume was 1.5 cm3 (range 0.09-21.54 cm3). CK SRS was delivered by a median marginal dose of 23 Gy (range 15-30 Gy) and a median of 3 fractions (range 1-5 fractions) to a median isodose line of 77% (range 70%-88%). The median biologically effective dose was 48 Gy (range 21-99.9 Gy) and the median follow-up was 30 months (range 3-95 months). The LTC at 1-, 2-, and 3-year follow-up was 86%, 65%, and 50%, respectively. The median progression-free survival and overall survival were 29 months (range 11-79 months) and 51 months (range 15-79 months), respectively. None of the patients presented adverse radiation effects., Conclusions: In the authors' experience, SRS provided excellent LTC without any adverse radiation effects for BMs secondary to ENB.

Introduction The morbidity sequelae of advanced cancer are often irreversible. Early palliative radiation can prevent, delay, and even improve these consequences. Treatment may be delayed due to a packed computed tomography (CT) simulation schedule or other logistics, including the cost and burden of arranging ambulance transportation when radiation centers are off-site. Objectives The primary objective was to determine the feasibility of using a recent diagnostic CT scan in lieu of a dedicated simulation CT to generate an adequate plan without sacrificing dosimetric goals and subsequent efficacy or tolerability. Secondary objectives included how much the lesion has grown, and how much earlier treatment could start if planned on a diagnostic CT scan. Materials/Methods For each inpatient treated with palliative radiation, a prior recent diagnostic CT scan was imported into the RayStation (RaySearch Laboratories, Stockholm, Sweden) planning system. From these diagnostic scans, planning treatment volumes (PTV) and organs at risk (OAR) were contoured using the same technique as the patient's actual treatment. The primary outcome was to compare both the PTV coverage and OAR dose between the plan generated from the diagnostic CT compared to that from the simulation CT. Our secondary outcomes include the mean time between CT simulation and first treatment, change in tumor volume between diagnostic scan and CT simulation, and the hottest 1% of each plan (D1). Results Between May and August 2019, a total of 22 inpatients were treated palliatively. Of those 22 patients, 10 patients (ages 32-92 years, median 64.5 years, 50% spine) met study criteria and had a diagnostic CT scan that was obtained within 14 days of simulation CT that was also compatible with our planning software. In the plans that were delivered, a mean of 98.8% (range 94.4-100%) of PTV was covered by at least 95% prescription dose. In the diagnostic CT plans, a mean of 95.4% (range 84.5-100%) of PTV was covered by at least 95% prescription dose. The difference between plans trended towards significance (p=0.061). When looking at patients receiving treatment to the spine or having a diagnostic CT within four days of the simulation CT, there was no statistically significant difference between the two plans (p=0.032 and 0.030, respectively). The OARs received, on average, 1.4% less mean radiation dose in the hypothetical plans (p=0.911). All OAR constraints were met in both groups. The mean time between diagnostic CT and CT simulation was 5.9 days and between CT simulation and first treatment was 1.9 days (range 0-5 days). The mean change in tumor volume was 22.64% smaller in the diagnostic CT scan plan. The D1 was an average 1% hotter in the hypothetical plans (p=0.16). Conclusion In hospitalized patients with an indication for palliative radiation, treatment planning on a pre-existing recent diagnostic CT scan produces comparable dose distributions without increases in dose to OARs when compared to the use of CT simulation scans, particularly for the treatment of the spine or when a very recent diagnostic CT is available. Bypassing CT simulation in select cases allows for earlier delivery of radiation with less patient and logistical burden. In combination with daily image guidance, this may translate to more timely delivery of radiation, less cost and burden to critically ill patients, and improved palliative benefit., Competing Interests: The authors have declared that no competing interests exist., (Copyright © 2021, Ho et al.)