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Purpose Achieving competency as educators is increasingly recognized as a critical part of residents’ training in graduate medical education across specialties. In addition to teaching medical students, radiation oncology residents often play a vital role in peer and interprofessional education. We conducted a survey to identify the needs of radiation oncology residents for developing skills in teaching. Methods and Materials An anonymous, web-based survey was developed and distributed to resident physicians at US radiation oncology programs. Analyses describe respondent demographics, experiences with teaching, and interest in various aspects of a formal “residents-as-teachers” curriculum. Results There were 171 completed survey responses (27.5% response rate). A total of 146 residents (85.4%) reported receiving no formal training in teaching before residency, and 121 (70.8%) reported no formal training during residency. Residents who had formal training in teaching were significantly more likely to be “quite” or “extremely” confident about teaching compared with residents who had no prior formal training (76.0% vs 51.4%; P = .022). Residents most commonly taught other residents and medical students (163 [95.3%] and 160 [93.6%] respondents, respectively). The most common settings for teaching were one-on-one teaching (164 respondents [95.9%]), small-group lectures (135 respondents [78.9%]), and intradepartmental lectures (136 respondents [79.5%]). In response to open-ended questions regarding desired teaching opportunities and domains for teaching development, many residents expressed a lack of confidence in teaching and were interested in improvement across many aspects of teaching. Conclusions Radiation oncology residents are expected and desire to teach in a multitude of settings across a wide variety of audiences. However, a significant proportion of radiation oncology residents lack formal training and rarely receive feedback for their teaching skills. The results of this national survey support the development of a residents-as-teachers curriculum for radiation oncology residents that would address the needs for and significant interest in this area.

Purpose/objective(s) Management of progressive brain tumors following high dose radiotherapy is controversial. In select cases, surgical resection can provide rapid relief of regional mass effect and edema, and highly focal adjuvant re-irradiation can be administered in the form of brachytherapy. Permanent low-dose rate cesium-131 brachytherapy may offer dosimetric and radiobiologic advantages over other isotopes. The purpose of this study was to examine the safety and efficacy of intracranial cesium-131 brachytherapy after surgical resection in a heavily pre-treated patient cohort. Materials/methods A retrospective chart review was conducted of all patients treated with intraoperative intracranial cesium-131 brachytherapy from an institutional database. Treatment consisted of maximal safe resection followed by implantation of suture-stranded cesium-131 seeds, maintaining approximately 10mm spacing between seeds, with a planned target dose of 80 Gy to 5mm depth. Local failure was defined as recurrence in or contacting the resection cavity after salvage resection and brachytherapy. Regional failure was defined as recurrence within 10mm of the resection cavity. Recurrence was defined as a new lesion or growth of ≥25% in any axial dimension on interval MRI. Toxicity was collected based on CTCAE 4.0. Results A total of 35 patients with a median imaging follow up of 17.0 months (interquartile range [IQR] 9.7-25.9) underwent 41 consecutive cesium-131 implants between 2016 and 2020. 20 patients (59%; N = 22 implants) were treated for recurrent brain metastasis, 12 patients (34%; N = 16 implants) were treated for recurrent atypical (N = 8) or anaplastic meningioma (N = 4), and 3 patients (9%) were treated for recurrent glioma (N = 2) or hemangiopericytoma (N = 1). A majority of lesions had received prior surgery (N = 28, 66.7%, range 0-3 prior surgeries) and 34 patients had received prior high dose radiation. 34 of 41 (82.9%) tumors had received prior radiosurgery, and 12 (29.2%) had undergone prior external beam radiation (range 50-60 Gy). 17 of 41 lesions (41.5%) had radiologic evidence of adverse radiation/treatment effect (ARE) prior to salvage therapy. Median tumor size was 3.0cm (IQR 2.3-3.7). Overall actuarial local/loco-regional control at 1-year was 91.6%/84.7% (89.8%/88.9% for metastases and 100%/82.5% for meningiomas). Crude loco-regional control was 86.3% for metastases, 75% for meningiomas, and 66.7% for other lesions. Symptomatic ARE following treatment was observed in 9.8% (N = 4) resection cavities. The surgical complication rate was 14.6% (N = 6 total, N = 3 [7.3%] grade 3-5) including 1 peri-operative death. Conclusion Cesium-131 brachytherapy in this heavily pre-treated cohort resulted in good local control and an acceptable rate of symptomatic adverse radiation effect and toxicity and may be a reasonable treatment option for this select population. Author disclosure W.C. Chen: None. M. Lafreniere: None. C. Phuong: None. M. Lometti: None. O. Morin: None. B.P. Ziemer: None. H. Vasudevan: Research Grant; Children's Tumor Foundation. Patent/License Fees/Copyright; Genentech, Eli Lilly. S. Hervey-Jumper: None. P.V. Theodosopoulos: None. S. Magill: None. S.E. Fogh: Independent Contractor; Accuray. J.L. Nakamura: None. L. Boreta: None. P.K. Sneed: None. M.W. McDermott: Chair; Miami Baptist. D. Raleigh: None. S.E. Braunstein: Advisory Board; Radiation Oncology Questions, LLC.

PURPOSE/OBJECTIVE(S) Previous studies have characterized dose gradient patterns for various hypo-fractionated brain radiosurgery (hSRS) treatment platforms. The Gamma Knife Icon (GKI) has consistently exhibited either superior or non-inferior peripheral dose fall-off and normal brain sparing characteristics when compared to other Linac-based hSRS treatment platforms. Given the prevalence of Linac-based treatments, identifying planning techniques to optimize treatment parameters is desirable. In this study, we investigated a novel Linac-based treatment approach that aimed to create the sharpest dose fall-off for hSRS of large brain lesions. MATERIALS/METHODS A cohort of patient cases (n = 10) with single brain lesions (volume 27.6+/-8.1 mL, range 20.-42.1 mL) treated with GKI at our institution were selected as sample test cases for our study. A non-coplanar unconstrained VMAT (NCU-VMAT) treatment planning approach was developed, and its script was implemented on a commercial treatment planning system for clinical Linac treatment equipped with the latest high-definition multi-leaf collimators (MLCs). Treatment plans produced via the NCU-VMAT approach were then compared against further optimized treatment plans from GKI, as well as conventional coplanar and non-coplanar VMAT treatment planning approaches. The comparison was carried out using DVH-derived parameters including target volume coverage, target dose conformity, modified dose fall-off index defined as the volume of 50% prescribed target dose divided by the target volume (PIV50). RESULTS For each case studied, NCU-VMAT achieved practically identical target coverage (0.98 ± 0.01) and Paddick dose conformity index (0.87 ± 0.02) compared to optimized GKI treatments. The mean PIV50 values were 2.99 ± 0.14, 3.77 ± 0.22, and 3.36 ± 0.19 for optimized GKI, conventional coplanar, and non-coplanar VMAT treatment plans, respectively. These results were in excellent agreement with previously published studies. However, the NCU-VMAT technique yielded a mean PIV50 of 2.41 ± 0.07. This represents an improvement of approximately 40% (P < 0.001, paired two-tailed Student t-test) over all existing approaches including GKI. Further analyses revealed that PIV50 of NCU-VMAT approached the theoretical minimum for all the studied cases. CONCLUSION Our results demonstrate that in treatment of large brain tumors, a treatment planning approach using Bremsstrahlung x-ray based Linacs can achieve superior dose fall-off for intracranial hSRS compared to GKI. We dispel the myth that physical characteristics of Cobalt γ-rays are needed to create the sharpest dose fall-off. Given the prevalence of Linac-based treatments compared to GKI, we present a novel optimized planning technique that achieves a new benchmark of sharpest dose fall-off. AUTHOR DISCLOSURE T. Nano: None. O. Morin: None. B.P. Ziemer: None. D. Raleigh: None. L. Boreta: None. J.L. Nakamura: None. S.E. Fogh: Independent Contractor; Accuray. P.K. Sneed: None. S. Hervey-Jumper: None. P.V. Theodosopoulos: None. S.E. Braunstein: Advisory Board; Radiation Oncology Questions, LLC.L. Ma: Patent/License Fees/Copyright; University of California Regents.

Purpose/Objective(s) To report our initial clinical implementation of a hypofractionated brain radiosurgery (hSRS) approach via packing hundreds of isocenters for treatment of a large target with a substantial GTV expansion in order to reduce dose hot spots in eloquent brain. Materials/Methods A high-density isocenter packing (HDIP) technique similar to “onion peeling” was developed for hSRS, where a large target volume of 14.1 cc was sequentially shrunk or “peeled” by a margin of 2 to 4-mm depending on its size. The isocenters were densely packed inside each layer or each “peel” of the target, especially within the GTV-to-PTV margin. Once packed, the isocenter location, shapes and weights of the beams were inversely optimized and manually adjusted to achieve an optimal dose distribution. This technique was clinically implemented on a frameless SRS unit for the purpose of expediting the workflow in treating brain lesions with GTV-to-PTV expansion of at least 5 mm. Results HDIP enabled the target dose to be prescribed to the 80-90% isodose line (normalized to the dose maximum), thus reducing dose hot spots greater than 120% of prescription dose inside the GTV expansion volume comprised mostly of normal brain tissue. Compared to the conventional approach of using only 1/3 to 1/4 as many isocenters, HDIP achieved identical dose coverage (> 98%), dose conformality ( 0.01 min to enable clinical implementation. This strategy negligibly impacted the total treatment time of 20-30 min of a typical HDIP treatment with a dose rate of 2.0 Gy/min of our LGKI unit. Conclusion HDIP is technically feasible and successfully implemented for the first time at our institution, enabling us to expedite the hSRS workflow to care for patients with targets in eloquent brain requiring substantial GTV-to-CTV/PTV margin expansion. Author Disclosure N. Cho: Employee; Thermo Fisher Scientific. D. Raleigh: None. B.P. Ziemer: None. T. Nano: None. P.V. Theodosopoulos: None. P.K. Sneed: None. L. Boreta: None. S.E. Braunstein: Advisory Board; Radiation Oncology Questions, LLC.L. Ma: Patent/License Fees/Copyright; University of California Regents.

BackgroundPrognostic markers for meningioma are needed to risk-stratify patients and guide postoperative surveillance and adjuvant therapy.ObjectiveTo identify a prognostic gene signature for meningioma recurrence and mortality after resection using targeted gene-expression analysis.MethodsTargeted gene-expression analysis was used to interrogate a discovery cohort of 96 meningiomas and an independent validation cohort of 56 meningiomas with comprehensive clinical follow-up data from separate institutions. Bioinformatic analysis was used to identify prognostic genes and generate a gene-signature risk score between 0 and 1 for local recurrence.ResultsWe identified a 36-gene signature of meningioma recurrence after resection that achieved an area under the curve of 0.86 in identifying tumors at risk for adverse clinical outcomes. The gene-signature risk score compared favorably to World Health Organization (WHO) grade in stratifying cases by local freedom from recurrence (LFFR, P

PURPOSE/OBJECTIVE(S) Patients with large brain metastases may receive fractionated stereotactic radiosurgery (FSRS) if they are not surgical candidates yet still pursuing cancer-directed therapy. FSRS with limited margins can allow for optimal sparing of uninvolved regional brain tissue. However, due to required treatment planning process, there is often elapsed time between MRI brain and treatment start which may contribute to marginal misses. Growth rates of large brain metastases and implications for optimal margin to account for growth rate and time interval between planning MRI and FSRS are incompletely characterized. MATERIALS/METHODS Patients treated at a single institution from 2018-2020 who received frameless FSRS on a Cobalt-60 treatment unit for large (> 2cm diameter) brain metastases were identified. Patients with a prior diagnostic brain MRI scan with technically similar parameters to a second MRI obtained for treatment planning were included. Resection cavities and lesions undergoing re-treatment after prior SRS were excluded. Brain metastasis volumes were obtained by contouring on both diagnostic and planning MRIs. Patient characteristics and treatment details were also collected. Analysis was conducted using paired Student's t test and Pearson's R and growth rate was determined using a linear model. RESULTS Thirty-six patients with 54 brain metastases met inclusion criteria. The most common primary cancer sites were lung (36%), colorectal (14%), and skin (14%), and most common histologies were adenocarcinoma (53%) and melanoma (17%). Nearly half (47%) of patients were on systemic therapy at the time of FSRS and the majority (85%) received steroids prior to starting FSRS. Treatment dose ranged from 24-32.5 Gy in 3-5 fractions, with median of 30 Gy in 5 fractions with zero margin. Median time from diagnostic to planning MRI was 15 days (IQR: 11-21) and planning MRI to FSRS was 1 day (IQR 1-3). The median size of included brain metastases on planning MRI was 7.38cc (IQR: 5.09-11.55) compared to 6.03cc (IQR: 3.87-8.95) on prior diagnostic MRI (P 90% of lesions over 3, 7, 10, and 14 days between planning and treatment, respectively. CONCLUSION In the absence of expedited planning, FSRT for intact large brain metastases with limited margins may result in geometric under treatment. An adaptive margin strategy based upon initial tumor size, and time between planning imaging and treatment delivery may be afforded to maintain ideal conformity, properly targeting a growing target lesion while maximally sparing uninvolved regional brain. AUTHOR DISCLOSURE J. Chew: None. S. Sinha: None. S.J. Liu: None. S.E. Fogh: Independent Contractor; Accuray. L. Boreta: None. D. Raleigh: None. L. Ma: Patent/License Fees/Copyright; University of California Regents. S.E. Braunstein: Advisory Board; Radiation Oncology Questions, LLC.

Purpose/Objective(s) Unchecked growth of brainstem metastases (BSM) can lead to acute morbidity and death. Stereotactic radiosurgery (SRS) remains the only local therapy for BSM, but the safety and efficacy of this approach are not fully understood, partly because BSM patients are excluded from many clinical trials. The aim of this study was to perform a systematic review and comparative meta-analysis of studies of SRS for BSM in the context of prospective trials of SRS or molecular/targeted therapy for non-brainstem brain metastases (BM). Materials/Methods A comprehensive search of the PubMed and Embase databases was performed on 12/6/19 following the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines to identify relevant studies of SRS for BSM, and prospective trials of SRS or molecular/targeted therapy for BM. Outcomes included 1-year local control (LC), objective response rate (ORR, defined as partial or complete response), 1-year overall survival (OS), neurologic death rate, and CTCAE 4.0 grade 3-5 adverse events. Pooled binomial proportions were estimated using a random effects model. Study heterogeneity was assessed using I2 and τ using the maximum likelihood method and the Wald test. Results A total of 32 retrospective studies with a study level median follow up of 8.5 months (interquartile range [IQR] 5.7-11.0) were identified comprising 1446 patients undergoing SRS for 1590 B.M.. Median BSM volume was 0.40cm3 (study level IQR 0.20-1.05cm3), and SRS treatments were delivered using fixed-frame radiosurgery (73.8%, median dose 16 Gy, range 6-30 Gy, median isodose 50%), linear accelerator (17.2%, median dose 13.7 Gy, range 11.1-39.0 Gy in 1-13 fractions, median isodose 85%), or robotic-arm radiosurgery (9%, median 17.5 Gy, range 16-24 in 1-5 fractions, median isodose 80%). Pooled 1-year LC was 86% (95% CI 83-88%, I2 = 38%), 1-year OS was 33% (30-37%, I2 = 35%), and the rate of grade 3-5 toxicity was 2.4% (1.5-3.7%, I2 = 33%). On univariate meta-regression, melanoma histology (coefficient 4.26, QM = 4.15, P = 0.042) and prior or concurrent WBRT (coefficient 1.62, QM = 3.98, P = 0.046) were associated with higher grade 3-5 toxicity from SRS for BSM. Deaths from BSM progression after SRS were rare (2.7%), and the neurologic death rate in BSM patients (24%, 19-31%, I2 = 62%) was not statistically different from the neurologic death rate in BM patients who were treated on prospective SRS trials (21%, 13-32%, I2 = 90%, N = 6 trials, Q = 0.36, P = 0.55). The pooled rate of ORR of 59% (47-71%, I2 = 88%) for SRS of BSM compared favorably to the wide range of intracranial ORR reported for molecular therapies (17-56%). Conclusion SRS for BSM is safe and effective, and the potential for acute morbidity or death from growth of untreated BSM is significant. The data here suggest SRS for BSM should be considered upon or prior to clinical trial enrollment of molecular/targeted therapy for BM. Author Disclosure W.C. Chen: None. U. Baal: None. J.D. Baal: None. J. Pai: None. H. Vasudevan: Research Grant; Children's Tumor Foundation. Patent/License Fees/Copyright; Genentech, Eli Lilly. L. Boreta: None. S.E. Braunstein: Advisory Board; Radiation Oncology Questions, LLC.D. Raleigh: None.

Purpose/Objective(s) The 2019 coronavirus pandemic (COVID-19) had a broad impact on the care of cancer patients, including the rapid adoption of telehealth video visits. On March 15, 2020, our institutional leadership recommended transition to video visits, which posed a risk of altering patients’ access to care. We assessed the impact of this rapid transition on demographic patterns in an urban academic radiation oncology department. Materials/Methods Consultation and follow-up visits from the pre-COVID-19 period (January 1, 2019 to March 14, 2020) and COVID-19 period (March 15, 2020 to August 31, 2020) in a single radiation oncology department were identified. Demographics and appointment data were abstracted from the institutional electronic health record. Time trends and patient and visit characteristics were compared across the pre-COVID-19 and COVID-19 periods. Results During the study period, 9,450 consult and follow-up visits were performed pre-COVID-19 and 3,298 visits in the COVID-19 period. The proportion of video visits increased markedly in the transition period, from 0.6% of all visits in the week of March 2, 2020, to 87% in the week of March 23, 2020. In-person visits decreased from 98% to 3%. Among all visits (in-person and telehealth), those during the COVID-19 period were less likely to be new consultations (43.1% from 60.1%; P < 0.001). There was a small and significant increase in the proportion of visits with patients who: identified as white (61.8% from 58.4%, P = 0.019), spoke English as their primary language (91.3% from 89.4%, P = 0.002), and had commercial insurance (34.1% from 32.0%; P = 0.009). Conclusion The overall COVID-19 clinic population retained demographic features similar to the pre-COVID-19 population despite a very rapid near-complete transition to telehealth. Nonetheless, the telehealth-predominant COVID-19 period had slightly increased visits with patients who were white or primarily English speaking or had commercial insurance. Strategies for ensuring telehealth is accessible to diverse populations should be a priority as telemedicine is integrated into long-term clinical operations.