Factors influencing local control after MR-guided stereotactic body radiotherapy (MRgSBRT) for adrenal metastases

Purpose

Stereotactic body radiotherapy (SBRT) is an effective treatment for adrenal gland metastases, but it is technically challenging and there are concerns about toxicity. We performed a multi-institutional pooled retrospective analysis to study clinical outcomes and toxicities after MR-guided SBRT (MRgSBRT) using for adrenal gland metastases.

Methods and Materials

Clinical and dosimetric data of patients treated with MRgSBRT on a 0.35 T MR-Linac at 11 institutions between 2016 and 2022 were analyzed. Local control (LC), local progression-free survival (LPFS), distant progression-free survival (DPFS) and overall survival (OS) were estimated using Kaplan-Meier method and log-rank test.

Results

A total of 255 patients (269 adrenal metastases) were included. Metastatic pattern was solitary in 25.9 % and oligometastatic in 58.0 % of patients. Median total dose was 45 Gy (range, 16-60 Gy) in a median of 5 fractions, and the median BED10 was 100 Gy (range, 37.5-132.0 Gy). Adaptation was done in 87.4 % of delivered fractions based on the individual clinicians' judgement. The 1- and 2- year LPFS rates were 94.0 % (95 % CI: 90.7-97.3 %) and 88.3 % (95 % CI: 82.4-94.2 %), respectively and only 2 patients (0.8 %) experienced grade 3 + toxicity. No local recurrences were observed after treatment to a total dose of BED10 > 100 Gy, with single fraction or fractional dose of > 10 Gy.

Conclusions

This is a large retrospective multi-institutional study to evaluate the treatment outcomes and toxicities with MRgSBRT in over 250 patients, demonstrating the need for frequent adaptation in 87.4 % of delivered fractions to achieve a 1- year LPFS rate of 94 % and less than 1 % rate of grade 3 + toxicity. Outcomes analysis in 269 adrenal lesions revealed improved outcomes with delivery of a BED10 > 100 Gy, use of single fraction SBRT and with fraction doses > 10 Gy, providing benchmarks for future clinical trials.

Predicting the Effect of Proton Beam Therapy Technology on Pulmonary Toxicities for Patients With Locally Advanced Lung Cancer Enrolled in the Proton Collaborative Group Prospective Clinical Trial

PURPOSE

This study aimed to predict the probability of grade ≥2 pneumonitis or dyspnea within 12 months of receiving conventionally fractionated or mildly hypofractionated proton beam therapy for locally advanced lung cancer using machine learning.

METHODS AND MATERIALS

Demographic and treatment characteristics were analyzed for 965 consecutive patients treated for lung cancer with conventionally fractionated or mildly hypofractionated (2.2-3 Gy/fraction) proton beam therapy across 12 institutions. Three machine learning models (gradient boosting, additive tree, and logistic regression with lasso regularization) were implemented to predict Common Terminology Criteria for Adverse Events version 4 grade ≥2 pulmonary toxicities using double 10-fold cross-validation for parameter hyper-tuning without leak of information. Balanced accuracy and area under the curve were calculated, and 95% confidence intervals were obtained using bootstrap sampling.

RESULTS

The median age of the patients was 70 years (range, 20-97), and they had predominantly stage IIIA or IIIB disease. They received a median dose of 60 Gy in 2 Gy/fraction, and 46.4% received concurrent chemotherapy. In total, 250 (25.9%) had grade ≥2 pulmonary toxicity. The probability of pulmonary toxicity was 0.08 for patients treated with pencil beam scanning and 0.34 for those treated with other techniques (P = 8.97e-13). Use of abdominal compression and breath hold were highly significant predictors of less toxicity (P = 2.88e-08). Higher total radiation delivered dose (P = .0182) and higher average dose to the ipsilateral lung (P = .0035) increased the likelihood of pulmonary toxicities. The gradient boosting model performed the best of the models tested, and when demographic and dosimetric features were combined, the area under the curve and balanced accuracy were 0.75 ± 0.02 and 0.67 ± 0.02, respectively. After analyzing performance versus the number of data points used for training, we observed that accuracy was limited by the number of observations.

CONCLUSIONS

In the largest analysis of prospectively enrolled patients with lung cancer assessing pulmonary toxicities from proton therapy to date, advanced machine learning methods revealed that pencil beam scanning, abdominal compression, and lower normal lung doses can lead to significantly lower probability of developing grade ≥2 pneumonitis or dyspnea.

How proton therapy fits into the management of adult intracranial tumors

Intracranial tumors include a challenging array of primary and secondary parenchymal and extra-axial tumors which cause neurologic morbidity consequential to location, disease extent, and proximity to critical neurologic structures. Radiotherapy can be used in the definitive, adjuvant, or salvage setting either with curative or palliative intent. Proton therapy (PT) is a promising advance due to dosimetric advantages compared to conventional photon radiotherapy with regards to normal tissue sparing, as well as distinct physical properties, which yield radiobiologic benefits. In this review, the principles of efficacy and safety of PT for a variety of intracranial tumors are discussed, drawing upon case series, retrospective and prospective cohort studies, and randomized clinical trials. This manuscript explores the potential advantages of PT, including reduced acute and late treatment-related side effects and improved quality of life. The objective is to provide a comprehensive review of the current evidence and clinical outcomes of PT. Given the lack of consensus and directives for its utilization in patients with intracranial tumors, we aim to provide a guide for its judicious use in clinical practice.

Management of sporadic intracanalicular vestibular schwannomas: A critical review and International Stereotactic Radiosurgery Society (ISRS) practice guidelines

BACKGROUND

The choice of an appropriate strategy for intracanalicular vestibular schwannoma (ICVS) is still debated. We conducted a systematic review and meta-analysis with the aim to compare treatment outcomes amongst management strategies (conservative surveillance (CS), microsurgical resection (MR), or stereotactic radiosurgery (SRS)) aiming to inform guideline recommendations on behalf of the International Stereotactic Radiosurgery Society (ISRS).

METHODS

Using PRISMA guidelines, we reviewed manuscripts published between January 1990 and October 2021 referenced in PubMed or Embase. Inclusion criteria were peer-reviewed clinical studies or case series reporting a cohort of ICVS managed with CS, MR, or SRS. Primary outcome measures included tumor control, the need for additional treatment, hearing outcomes, and posttreatment neurological deficits. These were pooled using meta-analytical techniques and compared using meta-regression with random effect.

RESULTS

Forty studies were included (2371 patients). The weighted pooled estimates for tumor control were 96% and 65% in SRS and CS series, respectively (P < .001). Need for further treatment was reported in 1%, 2%, and 25% for SRS, MR, and CS, respectively (P = .001). Hearing preservation was reported in 67%, 68%, and 55% for SRS, MR, and CS, respectively (P = .21). Persistent facial nerve deficit was reported in 0.1% and 10% for SRS and MR series, respectively (P = .01).

CONCLUSIONS

SRS is a noninvasive treatment with at least equivalent rates of tumor control and hearing preservation as compared to MR, with the caveat of better facial nerve preservation. As compared to CS, upfront SRS is an effective treatment in achieving tumor control with similar rates of hearing preservation.

Multi-institutional experience of MR-guided stereotactic body radiation therapy for adrenal gland metastases

Purpose

While dose escalation is associated with improved local control (LC) for adrenal gland metastases (AGMs), the proximity of gastrointestinal (GI) organs-at-risk (OARs) limits the dose that can be safely prescribed via CT-based stereotactic body radiation therapy (SBRT). The advantages of magnetic resonance-guided SBRT (MRgSBRT), including tumor tracking and online plan adaptation, facilitate safe dose escalation.

Methods

This is a multi-institutional review of 57 consecutive patients who received MRgSBRT on a 0.35-T MR linac to 61 AGMs from 2019 to 2021. The Kaplan-Meier method was used to estimate overall survival (OS), progression-free survival (PFS), and LC, and the Cox proportional hazards model was utilized for univariate analysis (UVA).

Results

Median follow up from MRgSBRT was 16.4 months (range [R]: 1.1-39 months). Median age was 67 years (R: 28-84 years). Primary histologies included non-small cell lung cancer (N = 38), renal cell carcinoma (N = 6), and melanoma (N = 5), amongst others. The median maximum diameter was 2.7 cm (R: 0.6-7.6 cm), and most AGMs were left-sided (N = 32). The median dose was 50 Gy (R: 30-60 Gy) in 5-10 fractions with a median BED10 of 100 Gy (R: 48-132 Gy). 45 cases (74 %) required adaptation for at least 1 fraction (median: 4 fractions, R: 0-10). Left-sided AGMs required adaptation in at least 1 fraction more frequently than right-sided AGMs (88 % vs 59 %, p = 0.018). There were 3 cases of reirradiation, including 60 Gy in 10 fractions (N = 1) and 40 Gy in 5 fractions (N = 2). One-year LC, PFS, and OS were 92 %, 52 %, and 78 %, respectively. On UVA, melanoma histology predicted for inferior 1-year LC (80 % vs 93 %, p = 0.012). There were no instances of grade 3+ toxicity.

Conclusions

We demonstrate that MRgSBRT achieves favorable early LC and no grade 3 + toxicity despite prescribing a median BED10 of 100 Gy to targets near GI OARs.

Clinical application of an institutional fractionated stereotactic radiosurgery (FSRS) program for brain metastases delivered with MRIdianⓇ BrainTx™

Single-fraction stereotactic radiosurgery (SRS) or fractionated SRS (FSRS) are well established strategies for patients with limited brain metastases. A broad spectrum of modern dedicated platforms are currently available for delivering intracranial SRS/FSRS; however, SRS/FSRS delivered using traditional CT-based platforms relies on the need for diagnostic MR images to be coregistered to planning CT scans for target volume delineation. Additionally, the on-board image guidance on traditional platforms yields limited inter-fraction and intra-fraction real-time visualization of the tumor at the time of treatment delivery. MR Linacs are capable of obtaining treatment planning MR and on-table MR sequences to enable visualization of the targets and organs-at-risk and may subsequently help identify anatomical changes prior to treatment that may invoke the need for on table treatment adaptation. Recently, an MR-guided intracranial package (MRIdian A3i BrainTxTM) was released for intracranial treatment with the ability to perform high-resolution MR sequences using a dedicated brain coil and cranial immobilization system. The objective of this report is to provide, through the experience of our first patient treated, a comprehensive overview of the clinical application of our institutional program for FSRS adaptive delivery using MRIdian's A3i BrainTx system-highlights include reviewing the imaging sequence selection, workflow demonstration, and details in its delivery feasibility in clinical practice, and dosimetric outcomes.

Radiation Therapy in the Management of Leptomeningeal Disease From Solid Tumors

Purpose

Leptomeningeal disease (LMD) is clinically detected in 5% to 10% of patients with solid tumors and is a source of substantial morbidity and mortality. Prognosis for this entity remains poor and treatments are palliative. Radiation therapy (RT) is an essential tool in the management of LMD, and a recent randomized trial demonstrated a survival benefit for proton craniospinal irradiation (CSI) in select patients. In the setting of this recent advance, we conducted a review of the role of RT in LMD from solid tumors to evaluate the evidence basis for RT recommendations.

Methods and Materials

In November 2022, we conducted a comprehensive literature search in PubMed, as well as a review of ongoing clinical trials listed on ClinicalTrials.gov, to inform a discussion on the role of RT in solid tumor LMD. Because of the paucity of high-quality published evidence, discussion was informed more by expert consensus and opinion, including a review of societal guidelines, than evidence from clinical trials.

Results

Only 1 prospective randomized trial has evaluated RT for LMD, demonstrating improved central nervous system progression-free survival for patients with breast and lung cancer treated with proton CSI compared with involved-field RT. Modern photon CSI techniques have improved upon historical rates of acute hematologic toxicity, but the overall benefit of this modality has not been prospectively evaluated. Multiple retrospective studies have explored the use of involved-field RT or the combination of RT with chemotherapy, but clear evidence of survival benefit is lacking.

Conclusions

Optimal management of LMD with RT remains reliant upon expert opinion, with proton CSI indicated in patients with good performance status and extra-central nervous system disease that is either well-controlled or for which effective treatment options are available. Photon-based CSI traditionally has been associated with increased marrow and gastrointestinal toxicities, though intensity modulated RT/volumetric-modulated arc therapy based photon CSI may have reduced the toxicity profile. Further work is needed to understand the role of radioisotopes as well as combined modality treatment with intrathecal or central nervous system penetrating systemic therapies.

Stereotactic Body Radiation Therapy for Hepatocellular Carcinoma: Meta-Analysis and International Stereotactic Radiosurgery Society Practice Guidelines

This systematic review and meta-analysis reports on outcomes and hepatic toxicity rates after stereotactic body radiation therapy (SBRT) for liver-confined hepatocellular carcinoma (HCC) and presents consensus guidelines regarding appropriate patient management. Using the Preferred Reporting Items for Systemic Review and Meta-Analyses guidelines, a systematic review was performed from articles reporting outcomes at ≥5 years published before October 2022 from the Embase, MEDLINE, Cochrane, and Scopus databases with the following search terms: ("stereotactic body radiotherapy" OR "SBRT" OR "SABR" OR "stereotactic ablative radiotherapy") AND ("hepatocellular carcinoma" OR "HCC"). An aggregated data meta-analysis was conducted to assess overall survival (OS) and local control (LC) using weighted random effects models. In addition, individual patient data analyses incorporating data from 6 institutions were conducted as their own subgroup analyses. Seventeen observational studies, comprising 1889 patients with HCC treated with ≤9 SBRT fractions, between 2003 and 2019, were included in the aggregated data meta-analysis. The 3- and 5-year OS rates after SBRT were 57% (95% confidence interval [CI], 47%-66%) and 40% (95% CI, 29%-51%), respectively. The 3- and 5-year LC rates after SBRT were 84% (95% CI, 77%-90%) and 82% (95% CI, 74%-88%), respectively. Tumor size was the only prognostic factor for LC. Tumor size and region were significantly associated with OS. Five-year LC and OS rates of 79% (95% CI, 0.74-0.84) and 25% (95% CI, 0.20-0.30), respectively, were observed in the individual patient data analyses. Factors prognostic for improved OS were tumor size <3 cm, Eastern region, Child-Pugh score ≤B7, and the Barcelona Clinic Liver Cancer stage of 0 and A. The incidence of severe hepatic toxicity varied according to the criteria applied. SBRT is an effective treatment modality for patients with HCC with mature follow-up. Clinical practice guidelines were developed on behalf of the International Stereotactic Radiosurgery Society (ISRS).

Commissioning Intracranial Stereotactic Radiosurgery for a Magnetic Resonance-Guided Radiation Therapy (MRgRT) System: MR-RT Localization and Dosimetric End-to-End Validation

PURPOSE

This is the first reporting of the MRIdian A3iTM intracranial package (BrainTxTM) and benchmarks the end-to-end localization and dosimetric accuracy for commissioning an magnetic resonace (MR)-guided stereotactic radiosurgery program. We characterized the localization accuracy between MR and radiation (RT) isocenter through an end-to-end hidden target test, relative dose profile intercomparison, and absolute dose validation.

METHODS AND MATERIALS

BrainTx consists of a dedicated head coil, integrated mask immobilization system, and high-resolution MR sequences. Coil and baseplate attenuation was quantified. An in-house phantom (Cranial phantOm foR magNetic rEsonance Localization of a stereotactIc radiosUrgery doSimeter, CORNELIUS) was developed from a mannequin head filled with silicone gel, film, and MR BB with pinprick. A hidden target test evaluated MR-RT localization of the 1×1×1 mm3 TrueFISP MR and relative dose accuracy in film for a 1 cm diameter (International Electrotechnical Commission (IEC)-X/IEC-Y) and 1.5 cm diameter (IEC-Y/IEC-Z) spherical target. Two clinical cases (irregular-shaped target and target abutting brainstem) were mapped to the CORNELIUS phantom for feasibility assessment. A 2-dimensional (2D)-gamma compared calculated and measured dose for spherical and clinical targets with 1 mm/1% and 2 mm/2% criteria, respectively. A small-field chamber (A26MR) measured end-to-end absolute dose for a 1 cm diameter target.

RESULTS

Coil and baseplate attenuation were 0.7% and 2.7%, respectively. The displacement of MR to RT localization as defined through the pinprick was 0.49 mm (IEC-X), 0.27 mm (IEC-Y), and 0.51 mm (IEC-Z) (root mean square 0.76 mm). The reproducibility across IEC-Y demonstrated high fidelity (<0.02 mm). Gamma pass rates were 97.1% and 95.4% for 1 cm and 1.5 cm targets, respectively. Dose profiles for an irregular-shaped target and abutting organ-at-risk-target demonstrated pass rates of 99.0% and 92.9%, respectively. The absolute end-to-end dose difference was <1%.

CONCLUSIONS

All localization and dosimetric evaluation demonstrated submillimeter accuracy, per the TG-142, TG-101, MPPG 9.a. criteria for SRS/SRT systems, indicating acceptable delivery capabilities with a 1 mm setup margin.

Advancing Beyond the Hippocampus to Preserve Cognition for Patients With Brain Metastases: Dosimetric Results From a Phase 2 Trial of Memory-Avoidance Whole Brain Radiation Therapy

Purpose

Recent advances to preserve neurocognitive function in patients treated for brain metastases include stereotactic radiosurgery, hippocampal avoidance whole brain radiation therapy (WBRT), and memantine administration. The hippocampus, corpus callosum, fornix, and amygdala are key neurocognitive substructures with a low propensity for brain metastases. Herein, we report our preliminary experience using a "memory-avoidance" WBRT (MA-WBRT) approach that spares these substructures for patients with >15 brain metastases.

Methods and Materials

Ten consecutive patients treated with MA-WBRT on a phase 2 clinical trial were reviewed. In each patient, the hippocampi, amygdalae, corpus callosum, and fornix were contoured. Patients were not eligible for MA-WBRT if they had metastases in these substructures. A memory-avoidance region was created using a 5-mm volumetric expansion around these substructures. Hotspots were avoided in the hypothalamus and pituitary gland. Coverage of brain metastases was prioritized over memory avoidance dose constraints. Dose constraints for these avoidance structures included a D100% ≤ 9 Gy and D0.03 cm3 ≤ 16 Gy (variation acceptable to 20 Gy). LINAC-based volumetric modulated arc therapy plans were generated for a prescription dose of 30 Gy in 10 fractions.

Results

On average, the memory avoidance structure volume was 37.1 cm3 (range, 25.2-44.6 cm3), occupying 2.5% of the entire whole brain target volume. All treatment plans met the D100% dose constraint, and 8 of 10 plans met the D0.03 cm3 constraint, with priority given to tumor coverage for the remaining 2 cases. Target coverage (D98% > 25 Gy) and homogeneity (D2% ≤ 37.5 Gy) were achieved for all plans.

Conclusions

Modern volumetric modulated arc therapy techniques allow for sparing of the hippocampus, amygdala, corpus callosum, and fornix with good target coverage and homogeneity. After enrollment is completed, quality of life and cognitive data will be evaluated to assess the efficacy of MA-WBRT to mitigate declines in quality of life and cognition after whole brain radiation.

Accelerated Hypofractionated Magnetic Resonance Guided Adaptive Radiation Therapy for Ultracentral Lung Tumors

Radiotherapy for ultracentral lung tumors represents a treatment challenge, considering the high rates of high-grade treatment-related toxicities with stereotactic body radiation therapy (SBRT) or hypofractionated schedules. Accelerated hypofractionated magnetic resonance-guided adaptive radiation therapy (MRgART) emerged as a potential game-changer for tumors in these challenging locations, in close proximity to central organs at risk, such as the trachea, proximal bronchial tree, and esophagus. In this series, 13 consecutive patients, predominantly male (n = 9), with a median age of 71 (range (R): 46-85), underwent 195 MRgART fractions (all 60 Gy in 15 fractions) to metastatic (n = 12) or primary ultra-central lung tumors (n = 1). The median gross tumor volumes (GTVs) and planning target volumes (PTVs) were 20.72 cc (R: 0.54-121.65 cc) and 61.53 cc (R: 3.87-211.81 cc), respectively. The median beam-on time per fraction was 14 min. Adapted treatment plans were generated for all fractions, and indications included GTV/PTV undercoverage, OARs exceeding tolerance doses, or both indications in 46%, 18%, and 36% of fractions, respectively. Eight patients received concurrent systemic therapies, including immunotherapy (four), chemotherapy (two), and targeted therapy (two). The crude in-field loco-regional control rate was 92.3%. No CTCAE grade 3+ toxicities were observed. Our results offer promising insights, suggesting that MRgART has the potential to mitigate toxicities, enhance treatment precision, and improve overall patient care in the context of ultracentral lung tumors.

A Systematic Review Informing the Management of Symptomatic Brain Radiation Necrosis After Stereotactic Radiosurgery and International Stereotactic Radiosurgery Society Recommendations

Radiation necrosis (RN) secondary to stereotactic radiosurgery is a significant cause of morbidity. The optimal management of corticosteroid-refractory brain RN remains unclear. Our objective was to summarize the literature specific to efficacy and toxicity of treatment paradigms for patients with symptomatic corticosteroid-refractory RN and to provide consensus guidelines for grading and management of RN on behalf of the International Stereotactic Radiosurgery Society. A systematic review of articles pertaining to treatment of RN with bevacizumab, laser interstitial thermal therapy (LITT), surgical resection, or hyperbaric oxygen therapy was performed. The primary composite outcome was clinical and/or radiologic stability/improvement (ie, proportion of patients achieving improvement or stability with the given intervention). Proportions of patients achieving the primary outcome were pooled using random weighted-effects analysis but not directly compared between interventions. Twenty-one articles were included, of which only 2 were prospective studies. Thirteen reports were relevant for bevacizumab, 5 for LITT, 5 for surgical resection and 1 for hyperbaric oxygen therapy. Weighted effects analysis revealed that bevacizumab had a pooled symptom improvement/stability rate of 86% (95% CI 77%-92%), pooled T2 imaging improvement/stability rate of 93% (95% CI 87%-98%), and pooled T1 postcontrast improvement/stability rate of 94% (95% CI 87%-98%). Subgroup analysis showed a statistically significant improvement favoring treatment with low-dose (below median, ≤7.5 mg/kg every 3 weeks) versus high-dose bevacizumab with regards to symptom improvement/stability rate (P = .02) but not for radiologic T1 or T2 changes. The pooled T1 postcontrast improvement/stability rate for LITT was 88% (95% CI 82%-93%), and pooled symptom improvement/stability rate for surgery was 89% (95% CI 81%-96%). Toxicity was inconsistently reported but was generally low for all treatment paradigms. Corticosteroid-refractory RN that does not require urgent surgical intervention, with sufficient noninvasive diagnostic testing that favors RN, can be treated medically with bevacizumab in carefully selected patients as a strong recommendation. The role of LITT is evolving as a less invasive image guided surgical modality; however, the overall evidence for each modality is of low quality. Prospective head-to-head comparisons are needed to evaluate the relative efficacy and toxicity profile among treatment approaches.

Stereotactic body radiotherapy for primary renal cell carcinoma: a systematic review and practice guideline from the International Society of Stereotactic Radiosurgery (ISRS)

Surgery is the standard of care for patients with primary renal cell carcinoma. Stereotactic body radiotherapy (SBRT) is a novel alternative for patients who are medically inoperable, technically high risk, or who decline surgery. Evidence for using SBRT in the primary renal cell carcinoma setting is growing, including several rigorously conducted prospective clinical trials. This systematic review was performed to assess the safety and efficacy of SBRT for primary renal cell carcinoma. Review results then formed the basis for the practice guidelines described, on behalf of the International Stereotactic Radiosurgery Society. 3972 publications were screened and 36 studies (822 patients) were included in the analysis. Median local control rate was 94·1% (range 70·0-100), 5-year progression-free survival was 80·5% (95% CI 72-92), and 5-year overall survival was 77·2% (95% CI 65-89). These practice guidelines addressed four key clinical questions. First, the optimal dose fractionation was 25-26 Gy in one fraction, or 42-48 Gy in three fractions for larger tumours. Second, routine post-treatment biopsy is not recommended as it is not predictive of patient outcome. Third, SBRT for primary renal cell carcinoma in a solitary kidney is safe and effective. Finally, guidelines for post-treatment follow-up are described, which include cross-axial imaging of the abdomen including both kidneys, adrenals, and surveillance of the chest initially every 6 months. This systematic review and practice guideline support the practice of SBRT for primary renal cell carcinoma as a safe and effective standard treatment option. Randomised trials with surgery and invasive ablative therapies are needed to further define best practice.

Prophylactic Radiation Therapy Versus Standard of Care for Patients With High-Risk Asymptomatic Bone Metastases: A Multicenter, Randomized Phase II Clinical Trial

PURPOSE

External-beam radiation therapy (RT) is standard of care (SOC) for pain relief of symptomatic bone metastases. We aimed to evaluate the efficacy of radiation to asymptomatic bone metastases in preventing skeletal-related events (SRE).

METHODS

In a multicenter randomized controlled trial, adult patients with widely metastatic solid tumor malignancies were stratified by histology and planned SOC (systemic therapy or observation) and randomly assigned in a 1:1 ratio to receive RT to asymptomatic high-risk bone metastases or SOC alone. The primary outcome of the trial was SRE. Secondary outcomes included hospitalizations for SRE and overall survival (OS).

RESULTS

A total of 78 patients with 122 high-risk bone metastases were enrolled between May 8, 2018, and August 9, 2021, at three institutions across an affiliated cancer network in the United States. Seventy-three patients were evaluable for the primary end point. The most common primary cancer types were lung (27%), breast (24%), and prostate (22%). At 1 year, SRE occurred in one of 62 bone metastases (1.6%) in the RT arm and 14 of 49 bone metastases (29%) in the SOC arm (P < .001). There were significantly fewer patients hospitalized for SRE in the RT arm compared with the SOC arm (0 v 4, P = .045). At a median follow-up of 2.5 years, OS was significantly longer in the RT arm (hazard ratio [HR], 0.49; 95% CI, 0.27 to 0.89; P = .018), which persisted on multivariable Cox regression analysis (HR, 0.46; 95% CI, 0.23 to 0.85; P = .01).

CONCLUSION

Radiation delivered prophylactically to asymptomatic, high-risk bone metastases reduced SRE and hospitalizations. We also observed an improvement in OS with prophylactic radiation, although a confirmatory phase III trial is warranted.

Management of Brain Metastases: A Review of Novel Therapies

Brain metastases (BMs) represent the most common intracranial tumors in adults, and most commonly originate from lung, followed by breast, melanoma, kidney, and colorectal cancer. Management of BM is individualized based on the size and number of brain metastases, the extent of extracranial disease, the primary tumor subtype, neurological symptoms, and prior lines of therapy. Until recently, treatment strategies were limited to local therapies, like surgical resection and radiotherapy, the latter in the form of whole-brain radiotherapy or stereotactic radiosurgery. The next generation of local strategies includes laser interstitial thermal therapy, magnetic hyperthermic therapy, post-resection brachytherapy, and focused ultrasound. New targeted therapies and immunotherapies with documented intracranial activity have transformed clinical outcomes. Novel systemic therapies with intracranial utility include new anaplastic lymphoma kinase inhibitors like brigatinib and ensartinib; selective "rearranged during transfection" inhibitors like selpercatinib and pralsetinib; B-raf proto-oncogene inhibitors like encorafenib and vemurafenib; Kirsten rat sarcoma viral oncogene inhibitors like sotorasib and adagrasib; ROS1 gene rearrangement (ROS1) inhibitors, anti-neurotrophic tyrosine receptor kinase agents like larotrectinib and entrectinib; anti-human epidermal growth factor receptor 2/epidermal growth factor receptor exon 20 agent like poziotinib; and antibody-drug conjugates like trastuzumab-emtansine and trastuzumab-deruxtecan. This review highlights the modern multidisciplinary management of BM, emphasizing the integration of systemic and local therapies.

Tumor treating fields: narrative review of a promising treatment modality for cancer

BACKGROUND AND OBJECTIVE

Tumor treating fields (TTFields) therapy have emerged as a potentially effective treatment for various malignancies by delivering low-intensity, intermediate-frequency electrical fields that disrupt many processes inside cells, resulting in the interruption of cell division in cancer cells. Additionally, TTFields therapy has been found to be synergistic with existing therapeutic approaches. In this review, we provide an introduction and background to the primary mechanisms of TTFields and discuss the emerging preclinical and clinical outcomes of this novel cancer treatment technology.

METHODS

We performed a literature search on PubMed, ClinicalTrials.Gov, and Google Scholar using the terms 'TTFields' and 'cancer'. We included studies, review articles, and editorials published in English from 1st January 2000 to 1st October 2023. All obtained publications were reviewed and their key references are cross-checked to ensure a balanced and high-quality review.

KEY CONTENT AND FINDINGS

Clinical studies reported to date have demonstrated the survival advantage of TTFields therapy in newly diagnosed glioblastoma (GBM), non-small cell lung cancer (NSCLC), and meaningful clinical activity in recurrent GBM (rGBM) and malignant pleural mesothelioma. Moreover, TTFields therapy has exhibited promising safety profiles across a diverse range of cancers including pancreatic cancer, hepatocellular carcinoma (HCC), ovarian cancer, NSCLC, and gastric cancer, when combined with cytotoxic chemotherapy and/or immunotherapy regimens, suggesting broad applicability as an added treatment modality.

CONCLUSIONS

Based on preclinical and clinical studies, TTFields therapy show promise as a potential treatment option for patients with a number of different malignancies, offering a favorable safety profile and the potential for significant clinical benefit. Further research is warranted to establish the optimal treatment parameters and identify specific patient subgroups that may derive the greatest advantage from this treatment modality.

Clinical trial implementation: a primer for neurosurgeons

In the current landscape of evidence-based medicine, prospective clinical trials are an important avenue through which to establish the efficacy and safety of biomedical treatments compared with standard-of-care interventions. Depending on their scope and aims, clinical trials can be extremely costly and time intensive, and significant coordination is needed to ensure optimal utilization of healthcare resources, adherence to the principles of biomedical ethics, and appropriate interpretation of study results. This review highlights the core principles for designing and implementing clinical trials within neurosurgery, with the aim to provide clinicians with a framework for implementing both investigator-initiated and industry-sponsored trials.

Surgically targeted radiation therapy (STaRT) for recurrent brain metastases: Initial clinical experience

PURPOSE

This study evaluates the outcomes of recurrent brain metastasis treated with resection and brachytherapy using a novel Cesium-131 carrier, termed surgically targeted radiation therapy (STaRT), and compares them to the first course of external beam radiotherapy (EBRT).

METHODS

Consecutive patients who underwent STaRT between August 2020 and June 2022 were included. All patients underwent maximal safe resection with pathologic confirmation of viable disease prior to STaRT to 60 Gy to a 5-mm depth from the surface of the resection cavity. Complications were assessed using CTCAE version 5.0.

RESULTS

Ten patients with 12 recurrent brain metastases after EBRT (median 15.5 months, range: 4.9-44.7) met the inclusion criteria. The median BED10Gy90% and 95% were 132.2 Gy (113.9-265.1 Gy) and 116.0 Gy (96.8-250.6 Gy), respectively. The median maximum point dose BED10Gy for the target was 1076.0 Gy (range: 120.7-1478.3 Gy). The 6-month and 1-year local control rates were 66.7% and 33.3% for the prior EBRT course; these rates were 100% and 100% for STaRT, respectively (p < 0.001). At a median follow-up of 14.5 months, there was one instance of grade two radiation necrosis. Surgery-attributed complications were observed in two patients including pseudomeningocele and minor headache.

CONCLUSIONS

STaRT with Cs-131 presents an alternative approach for operable recurrent brain metastases and was associated with superior local control than the first course of EBRT in this series. Our initial clinical experience shows that STaRT is associated with a high local control rate, modest surgical complication rate, and low radiation necrosis risk in the reirradiation setting.

Online adaptive radiotherapy: Assessment of planning technique and its impact on longitudinal plan quality robustness in pancreatic cancer

BACKGROUND AND PURPOSE

Planning on a static dataset that reflects the simulation day anatomy is routine for SBRT. We hypothesize the quality of on-table adaptive plans is similar to the baseline plan when delivering stereotactic MR-guided adaptive radiotherapy (SMART) for pancreatic cancer (PCa).

MATERIALS AND METHODS

Sixty-seven inoperable PCa patients were prescribed 50 Gy/5-fraction SMART. Baseline planning included: 3-5 mm gastrointestinal (GI) PRV, 50 Gy optimization target (PTVopt) based on GI PRV, conformality rings, and contracted GTV to guide the hotspot. For each adaptation, GI anatomy was re-contoured, followed by re-optimization. Plan quality was evaluated for target coverage (TC = PTVopt V100%/volume), PTV D90% and D80%, homogeneity index (HI = PTVopt D2%/D98%), prescription isodose/target volume (PITV), low-dose conformity (D2cm = maximum dose at 2 cm from PTVopt/Rx dose), and gradient index (R50%=50% Rx isodose volume/PTVopt volume).A novel global planning metric, termed the Pancreas Adaptive Radiotherapy Score (PARTS), was developed and implemented based on GI OAR sparing, PTV/GTV coverage, and conformality. Adaptive robustness (baseline to fraction 1) and stability (difference between two fractions with highest GI PRV variation) were quantified.

RESULTS

OAR constraints were met on all baseline (n = 67) and adaptive (n = 318) plans. Coverage for baseline/adaptive plans was mean ± SD at 44.9 ± 5.8 Gy/44.3 ± 5.5 Gy (PTV D80%), 50.1 ± 4.2 Gy/49.1 ± 4.7 Gy (PTVopt D80%), and 80%±18%/74%±18% (TC), respectively. Mean homogeneity and conformality for baseline/adaptive plans were 0.87 ± 0.25/0.81 ± 0.30 (PITV), 3.81 ± 1.87/3.87 ± 2.0 (R50%), 1.53 ± 0.23/1.55 ± 0.23 (HI), and 58%±7%/59%±7% (D2cm), respectively. PARTS was found to be a sensitive metric due to its additive influence of geometry changes on PARTS' sub-metrics. There were no statistical differences (p > 0.05) for stability, except for PARTS (p = 0.04, median difference -0.6%). Statistical differences for robustness when significant were small for most metrics (<2.0% median). Median adaptive re-optimizations were 2.

CONCLUSION

We describe a 5-fraction ablative SMART planning approach for PCa that is robust and stable during on-table adaption, due to gradients controlled by a GI PRV technique and the use of rings. These findings are noteworthy given that daily interfraction anatomic GI OAR differences are routine, thus necessitating on-table adaptation. This work supports feasibility towards utilizing a patient-independent, template on-table adaptive approach.

A study on inter-planner plan quality variability using a manual planning- or Lightning dose optimizer-approach for single brain lesions treated with the Gamma Knife® Icon™

PURPOSE

The purpose of this study is to investigate inter-planner plan quality variability using a manual forward planning (MFP)- or fast inverse planning (FIP, Lightning)-approach for single brain lesions treated with the Gamma Knife® (GK) Icon™.

METHODS

Thirty patients who were previously treated with GK stereotactic radiosurgery or radiotherapy were selected and divided into three groups (post-operative resection cavity, intact brain metastasis, and vestibular schwannoma [10 patients per group]). Clinical plans for the 30 patients were generated by multiple planners using FIP only (1), a combination of FIP and MFP (12), and MFP only (17). Three planners (Senior, Junior, and Novice) with varying experience levels re-planned the 30 patients using MFP and FIP (two plans per patient) with planning time limit of 60 min. Statistical analysis was performed to compare plan quality metrics (Paddick conformity index, gradient index, number of shots, prescription isodose line, target coverage, beam-on-time (BOT), and organs-at-risk doses) of MFP or FIP plans among three planners and to compare plan quality metrics between each planner's MFP/FIP plans and clinical plans. Variability in FIP parameter settings (BOT, low dose, and target max dose) and in planning time among the planners was also evaluated.

RESULTS

Variations in plan quality metrics of FIP plans among three planners were smaller than those of MFP plans for all three groups. Junior's MFP plans were the most comparable to the clinical plans, whereas Senior's and Novice's MFP plans were superior and inferior, respectively. All three planners' FIP plans were comparable or superior to the clinical plans. Differences in FIP parameter settings among the planners were observed. Planning time was shorter and variations in planning time among the planners were smaller for FIP plans in all three groups.

CONCLUSIONS

The FIP approach is less planner dependent and more time-honored than the MFP approach.

Integration of an App-Based Cognitive Evaluation Program into Radiosurgery Practice: Outcomes and Patient Survey Analysis from a Prospective Observational Study

PURPOSE/OBJECTIVE(S)

Cognitive decline is a significant consequence of stereotactic radiosurgery (SRS) in patients with brain metastases. This is often underrecognized and understudied outside of a formal clinical trial setting as traditional methods are often logistically difficult and need specialized personnel and additional time. To address these challenges, we implemented a prospective study (NCT05504681), incorporating an innovative app-based solution to monitor patient assessments over time, collect patient data easily, and be suitable for cross-cultural use in multiple languages for monitoring post-SRS cognitive decline.

MATERIALS/METHODS

Patients undergoing SRS from December 2021 to October 2022 were enrolled in this study and completed feedback surveys. The assessments consisted of learning and memory (Hopkins verbal learning test-revised [HVLT-R]), attention and processing speed (Digit symbols modalities test [SDMT]), verbal fluency (Controlled oral word association test [COWAT]) and executive function (Trail making test [TMT]). Baseline and 3-month follow-up testing were conducted in conjunction with routine imaging and clinical assessments. Neurocognitive deterioration (ND) was defined as a decrease of ≥2 standard errors of the mean in any of the tests, without evidence of new intracranial disease. Any differences between the baseline and follow-up assessments were confirmed using the reliable change index.

RESULTS

A total of 30 patients with median age of 68 (range: 47-87) were enrolled. The median KPS was 90 and 60% were female. 43% of participants had a high school or equivalent level of education. 19 (63%) patients were Hispanic and 43% tested in Spanish. The median number of treated lesions was 2 (1-13) and 7 (23%) patients were treated to ≥5 lesions. The median mean left and right hippocampal doses were 0.3 Gy (0-3 Gy) and 0.2 Gy (0-5.2 Gy), respectively. Overall, 50% of patients met criteria for ND at 3 months. 20% of patients showed ND in HVLT-R-immediate recall (IMM), 23% in HVLT-R-delayed recall (DR), 13% in HVLT-R-recognition (Rec), 3% in COWAT and 20% in TMT. None of the patients had ND in SDMT. The mean relative decline was 28% for HVLT-R- IMM, 34% for HVLT-R-DR, 6% for HVLT-R- Rec, 25% for COWAT, and 21% for TMT. There was no significant association between the number of treated lesions and ND. Based on the feedback results, the majority of patients found the system easy to use (94%) and relevant to their care (73%). Most patients reported that app-based evaluation improved discussions with clinicians (77%), made them feel more in control of their care (79%), and they would recommend the system to other patients (87%).

CONCLUSION

Our study showed a high incidence of ND using an app-based tool in a patient who underwent SRS and from diverse education and language backgrounds. Patient survey results demonstrated that the tool was easy to use and relevant to the patient's care, especially due to improvements in discussions with clinicians and a sense of being in control of their own care.

Stereotactic Radiosurgery for Small Intact Brain Metastasis: A Comparative Evaluation of 3 Different Single Fraction Prescription Doses

PURPOSE/OBJECTIVE(S)

While single-fraction stereotactic radiosurgery (SRS) in the treatment of small brain metastases (SBM, ≤ 2 cm) is well established, prescription dosing varies considerably across institutions and clinical trials. The choice of prescription dose is a delicate balance between local failure (LF) and radiation necrosis (RN) risks. In the modern era, historically-established dosing thresholds may no longer be applicable. To evaluate the impact of prescription dose on outcomes, we performed a comparative analysis of patients with SBM treated with definitive SRS using three different prescriptions, at a single tertiary institution.

MATERIALS/METHODS

Consecutive patients with intact SBM treated with SRS from January 2017 and December 2021 were analyzed. Baseline patient characteristics and dosing parameters were abstracted from the medical record. To limit the integral brain dose when treating multiple brain metastases, the institutional practice was to reduce prescription dose as the total number of lesions increased (i.e., 24 Gy for ≤10 lesions, 22 Gy for 11-20, and 20 Gy for >20). A per lesion analysis, where each lesion was followed from the date of SRS to the last follow-up, was conducted with primary endpoints of LF and RN. Gray's test was used to compare the cumulative incidence of the LF and RN, with death as a competing risk. Factors affecting LF were analyzed using Cox hazard regression analysis.

RESULTS

A total of 1318 SBM in 250 patients received SRS and met the inclusion criteria. The median age was 62 years (range: 18-90), median KPS was 90 (range: 50-100) and 66% were female. The most common primary tumors were lung (55.5%) and breast cancers (26.4%). With a median follow-up of 12 months, 136 (11%) LF in 44 patients and 70 (5.7%) RN events in 46 patients occurred. The actuarial 1-year cumulative rate of LF was lower in lesions treated with 24 Gy (6.4%, 95% CI: 4.7-8.6%) or 22 Gy (5.8%, 95% CI: 3.7-8.7%) compared to 20 Gy (15.4%, 95% CI: 10.9-20.5%) (p<0.01). 22 Gy and 24 Gy prescription doses were associated with a 44% and 52% reduction in risk in LF compared to 20 Gy (HR: 0.56; 95% CI: 0.36-0.9; p = 0.01 and HR: 0.48; 95% CI: 0.31-0.74; p<0.01, respectively). In a subset analysis of radiosensitive tumors, 1-year LF rate was still lower with 24 Gy (7.4%, 95% CI: 5.3-9.9%) and 22 Gy (6.1%, 95% CI: 3.7-9.4%) than 20 Gy (15.7%, 95% CI: 11.2-21%) (p = 0.01). The cumulative 1-year RN rate numerically declined with dose, but was not statistically significantly different, with 3.6% (95% CI: 2.3-5.3%) for 24 Gy, 2.6% (95% CI: 1.3-4.8%) for 22 Gy and 1.4% (95% CI: 0.4-3.7%) for 20 Gy.

CONCLUSION

Patients treated with single fraction SRS to intact SBM were at increased risk of LF with prescription doses of 20 Gy compared to 22-24 Gy, without an increased risk of RN. Even in patients with radiosensitive histologies, higher LF rates were still observed following 20 Gy compared to 22-24 Gy.

A Comparison of Local Failure and Necrosis Following Different Radiosurgery Strategies for Large Brain Metastases

PURPOSE/OBJECTIVE(S)

Large brain metastases (LBMs) are associated with poor local control with single-fraction stereotactic radiosurgery (SRS) alone. Various alternative strategies have been developed, including fractionated SRS (FSRS) and staged SRS (SSRS) for intact LBMs, and resection with postoperative-SRS (postop-SRS) or preoperative-SRS (preop-SRS) for operable LBMs. The objective of this study is to compare local failure (LF) and radiation necrosis (RN) outcomes among these four management strategies to determine the optimal treatment paradigm.

MATERIALS/METHODS

Consecutive patients diagnosed with LBM (≥2 cm in maximum dimension) between July 2017 and January 2022 and treated with one of the aforementioned strategies at a single tertiary institution were evaluated. All immobilization, target contouring, margins, dose- and prescription selection followed pre-defined institutional guidelines. Primary endpoints included LF, symptomatic RN, or a composite endpoint of these two variables. Gray's test was used to compare the cumulative incidence of the LF and the composite endpoint, with death as a competing risk.

RESULTS

A total of 234 LBMs in 188 consecutive patients met the inclusion criteria. The median age was 65 years (range: 31-98), the median KPS was 80 (range: 50-100), and 58% were female. The most common primary tumors were lung (48%) and breast cancer (17%). The median maximum tumor diameter was 3.0 cm (range: 2.0-5.6). 47 (20%) lesions were treated with FSRS, 66 (28%) with SSRS, 74 (32%) with postop-SRS, and 47 (20%) with preop-SRS. With a median follow-up of 12 months, 22 (9%) LF and 11 (5%) RN events occurred. The 6-month and 1-year cumulative incidences of LF for the entire cohort were 5% (95% CI: 3%-9%) and 8% (95% CI: 5%-12%), respectively. The 6-month and 1-year LF rates were 4% (95% CI: 1%-13%) and 8% (95% CI: 3%-20%) for FSRS; 8% (95% CI: 3%-20%) and 8% (95% CI: 3%-20%) for SSRS; 7% (95% CI: 3%-15%) and 8% (95% CI: 3%-16%) for postop-SRS; 0 and 7% (95% CI: 2%-20%) for preop-SRS (p>0.05). The 1-year OS rates were favorable in resected patients (61% for postop-SRS and 82% for preop-SRS) compared to SRS alone strategies (45% for FSRS and 56% for SSRS) (p = 0.004). Similarly, RN events were significantly lower in resected patients treated with either bimodality approach (0 for postop-SRS and 4% for preop-SRS) than SRS standalone strategies (9% for FSRS and 8% SSRS) (p = 0.024). At 12 months, the cumulative probabilities of the composite endpoint were 13% (95% CI: 5%-25%) for FSRS, 15% (95% CI: 7%-25%) for SSRS, 9% (95% CI: 3%-17%) for postop-SRS, and 12% (95% CI: 4%-24%) for preop-SRS and not significantly different between the groups.

CONCLUSION

For medically operable patients with surgically resectable LBMs, a strategy of surgery and SRS, regardless of timing, is associated with favorable local control and reduced risk for RN. For unresected patients, either SSRS or FSRS is associated with similar local control, but slightly higher RN risk. Prospective comparative evaluation is warranted.

Surgically Targeted Radiation Therapy (STaRT) for Brain Metastases: Initial Experience from a Prospective Multi-Institutional Registry

PURPOSE/OBJECTIVE(S)

Resection and intraoperative brachytherapy for patients with large, operable brain metastasis allows for both relief of mass effect and the delivery of radiotherapy (RT) to the resection cavity with a favorable dosimetric profile. The objective of this study was to analyze early patterns-of-care and treatment-related toxicity outcomes for brain metastasis patients treated with surgically targeted radiation therapy (STaRT) using a novel brachytherapy carrier.

MATERIALS/METHODS

Patients with brain metastasis, de novo and recurrent disease, who enrolled onto a prospective multi-institutional observational study (NCT04427384) were the subject of this analysis. Patients underwent resection and immediate implantation of bioresorbable, conformable, 20 mm x 20 mm x 4 mm collagen tile brachytherapy device(s) containing four uniform-intensity Cesium-131 sources. Toxicities were categorized using the CTCAE v5.0 adverse event (AE) criteria.

RESULTS

From 10/2020 to 01/2023, 13 participating sites enrolled and treated 48 patients with 51 metastases (13 with de novo and 35 patients with recurrent brain metastases), and 3 patients had 2 lesions implanted at the same procedure. Median age was 61 years (range: 28-80), 52% were female, and the most common primary types were lung (56%) and breast (13%). The median maximum pre-operative dimension was 3.4 cm (range: 1.7-5.7) and median pre-operative tumor volume 13.7cm3 (range: 1.7-132). 64% had received prior RT with a median time from last RT to STaRT of 14.6 months range: 3.5-57.3). Median KPS at screening was 80 (range: 50-100), and remained stable at post op visit (80, range: 50-100), and at 3-months following treatment (80, range 50-100), respectively (p>0.05). The median time for implantation was 3 minutes (range: 0.4-30). At a median follow-up of 4 months (range: <1-18), no patient experienced a radiation-attributed AE, and only 1 attributable Gr >3 AE was noted (Gr 5 intracerebral hemorrhage deemed probably related to surgery and unrelated to the implanted device).

CONCLUSION

Early results from this prospective multi-center trial demonstrate the feasibility and safety of STaRT. The lack of radiation-related AE, even with short follow-up, is intriguing given the relatively large lesion size and proportion of patients treated for recurrent, previously irradiated disease. Additional follow-up will provide data on tumor control outcomes and radiation necrosis rates using this novel technique.

Advancing beyond the Hippocampus to Preserve Cognition for Patients with Brain Metastases: Dosimetric Results from a Phase 2 Trial of Memory-Avoidance Whole Brain Radiotherapy

PURPOSE/OBJECTIVE(S)

Recent advances to preserve neurocognitive function in patients treated for brain metastases include stereotactic radiosurgery (SRS), hippocampal avoidance whole brain radiation therapy (HA-WBRT), and memantine administration. However, 23% of patients receiving HA-WBRT and memantine on NRG-CC001 still experienced executive function deterioration at 4 months, with 12% experiencing total recall and delayed recognition deterioration at 6 months. The hippocampus, corpus callosum, fornix, and amygdala are key neurocognitive substructures with a low propensity for brain metastases. Herein, we report our preliminary experience using an advanced "memory-avoidance" WBRT (MA-WBRT) approach sparing these substructures for patients with multiple (>15) brain metastases.

MATERIALS/METHODS

Ten consecutive patients treated with MA-WBRT on a phase 2 clinical trial (OSU-21074) were reviewed. In each patient, the hippocampi, amygdalae, corpus callosa, and fornix were contoured. Patients were not eligible for MA-WBRT if they had metastases in these substructures. A memory- avoidance region created using a 5mm volumetric expansion around these substructures. Hotspots were avoided in the hypothalamus and pituitary gland. Dose constraints for these avoidance structures were modeled after NRG CC-001 and include a D100% ≤ 9 Gy and a D0.03 cc ≤ 16 (acceptable to 20 Gy). Coverage of brain metastases was prioritized over memory avoidance dose constraints. Linac-based volumetric modulated arc therapy (VMAT) plans were generated for a prescription dose of 30 Gy in 10 fractions.

RESULTS

On average, the memory avoidance structure volume was 37.1 ccs (Range: 25.2-44.6 ccs), occupying 2.5% of the entire whole brain target volume. All treatment plans met the D100% dose constraint, and 8/10 plans met the D0.03cc constraint, with priority given to tumor coverage for the remaining 2 cases. VMAT spared the memory avoidance structures with a median dose range of 10.8-14.2 Gy and a maximum dose (D0.03cc) range of 15.6-22.7 Gy. The mean dose to the memory avoidance structures was 12.7 Gy (Range: 11.5-13.8 Gy). Target coverage (D98% > 25 Gy) and homogeneity (D2% ≤ 37.5 Gy) were achieved for all plans.

CONCLUSION

Modern VMAT techniques allow for sparing of the hippocampus, amygdala, corpus callosum, and fornix with good target coverage and homogeneity. Prospective quality of life and cognitive data including are being collected and include the Functional Assessment of Cancer Therapy - Brain (Fact-Br), Hopkins Verbal Learning Test (HLVT-R), Trail Making Test A/B (TMT-A/B) and Controlled Oral Word Association Test (COWAT). After enrollment is completed, these data will be evaluated to assess the efficacy of MA-WBRT to mitigate declines in quality of life and cognition after whole brain radiation.

Outcomes of MR-Guided Stereotactic Body Radiotherapy (MRgSBRT) for Adrenal Metastases: A Multi-Institutional Pooled Analysis

PURPOSE/OBJECTIVE(S)

Stereotactic body radiotherapy (SBRT) is an effective treatment for adrenal metastases, but it is technically challenging and there are concerns about toxicity due to the proximity of organs at risk. We hypothesized that MR-guided SBRT (MRgSBRT) using a 0.35 T MR-Linac for adrenal metastases can achieve durable local control (LC) with a low probability of toxicity.

MATERIALS/METHODS

In an ethics-approved study, we analyzed clinical and dosimetric data of patients treated with MRgSBRT at 10 institutions between 2016-2022. LC, local progression-free survival (LPFS), distant progression-free survival (DPFS) and overall survival (OS) were estimated using Kaplan-Meier method and log-rank test. Responses were evaluated using RECIST criteria. Toxicity was graded according to CTCAE (v4.0). OS and DPFS were calculated on a per-patient basis, while LC and LPFS were calculated on a per-lesion basis.

RESULTS

A total of 249 patients (260 adrenal lesions) were included; median age was 65 years (range 28-91), 65.5% were male, 83.9% had ECOG PS 0-1. The most common primary tumor was lung cancer (69.1%). Adrenal metastases were synchronous, metachronous, oligoprogressive or oligopersistent in 20%, 41.5%, 35.8% and 2.7% of patients, respectively. Metastatic pattern was solitary in 26.9%, oligometastatic in 57.3% and polymetastatic in 15.8% of patients. Right-sided metastases comprised 40%, left-sided 51.5% and lesions were bilateral in 8.5%. Chemotherapy and immunotherapy were administered in 67.1% and 60.6% of patients, respectively. Median gross tumor volume was 21.8 cc (range 1.1-383.2) and median planning target volume was 36.9 cc (range 3.6-516.9). Median total dose was 45 Gy (range 16-60), median fraction number was 5 (range 1-8) and median fraction dose used was 10 Gy (range 5-24). Median BED10 was 100 Gy (range 37.5-132); 87.8% of fractions used adapted plans. At a median follow-up was 17.7 months (IQR 5.5-21.7), local responses were scored as complete response (CR), partial response (PR), stable disease (SD) or progressive disease (PD) in 36.9%, 28.2%, 25.7%, and 9.1%, respectively. Median OS was 30.4 months, with 1- and 2- year OS rates of 75.3% and 57.1%, respectively. On multivariate analysis, significantly higher OS rates were seen in patients achieving a CR (p = 0.007, HR 0.50) and with ECOG scores of 0-1 (p = 0.001, HR 0.43). One- and 2- year LPFS rates were 94.5% and 88.8%, respectively. No local recurrences were observed after treatment to a BED10>100 or with single fraction (range 16-24 Gy). Only 2 patients (0.8%) had ≥grade 3 chronic toxicity.

CONCLUSION

This multi-institutional study of MRgSBRT outcomes for adrenal metastases revealed a 2-year LPFS of 89%, with a <1% risk of ≥grade 3 toxicity. Daily adaptation was performed in 90% of plans, indicating a beneficial role for MR guidance.

Patterns of Locoregional Failure After Ablative 5-Fraction Stereotactic MR-Guided on-Table Adaptive Radiation Therapy for Pancreatic Cancer

PURPOSE/OBJECTIVE(S)

SBRT for pancreatic ductal adenocarcinoma (PDAC) is routinely delivered with non-ablative dose to only gross disease resulting in locoregional failure (LRF) rates of >50%, most commonly near the celiac artery (CA) and/or superior mesenteric artery (SMA). It is unclear whether an alternative approach of prescribing ablative dose to gross disease plus elective coverage prevents and/or delays LRF. The study objective was to describe the incidence and anatomic distribution of LRF using this treatment approach.

MATERIALS/METHODS

A single institution retrospective analysis was performed of non-metastatic PDAC patients who received ablative stereotactic MR-guided on-table adaptive radiation therapy (A-SMART) on a 0.35T MR-Linac from 2018-2022. Median prescribed dose was 50 Gy/5 fractions. Elective coverage (EC), including a margin around the primary tumor, CA, and SMA, to 33-35 Gy/5 fractions became routine in 2019 using a simultaneous integrated boost; the porta hepatis was not routinely covered. LRFs were contoured and defined as out-of-field (OOF), marginal (M), or in-field (IF) if >80%, 20-80%, or <20% of it was outside of the most peripheral prescription isodose line.

RESULTS

One hundred four patients were evaluated (87% head tumors). 94% had induction chemotherapy (median 4 months), usually FOLFIRINOX (66%) or gemcitabine/nab-paclitaxel (27%). 88% received EC. Median GTV, CTV, PTVgrosstumor, and PTVelective volumes were 29 cc, 90 cc, 64 cc, and 127 cc, respectively. 16 patients (15%) had LRF after a median of 17 months (range: 2.4-30.8) from A-SMART; 13 had scans available for delineating LRF. Median follow-up from A-SMART for the entire cohort vs. LRF was 12 vs. 24 months. LRF involved the primary tumor (31%), retroperitoneal lymph nodes (25%), SMA (19%), porta hepatis (19%), and CA (6%). LRF was OOF, M, or IF in 30.8% (n = 4), 61.5% (n = 8), and 7.7% (n = 1). Distance from the 3 SMA failures to SMA origin was 10 cm (EC used), 9.3 cm (EC used), and 3 cm (no EC). The 1 CA failure involved the CA origin (no EC). Median mean, maximum, and minimum dose of the contoured LRF region on the original plan was 33.3 Gy (range: 9.7-50.3 Gy), 56 Gy (range: 44.2-71.4 Gy), and 11.4 Gy (range: 1.2-22.7 Gy), respectively. Median V20, V25, V30, V35, and V40 of the contoured LRF was 84.3% (range: 16.1-100%), 69.2% (range: 12.5-99.7%), 57.5% (range: 9.3-95.5%), 41.2% (range: 6.8-84.0%), and 32.7% (range: 4.8-71.8%).

CONCLUSION

This study represents the first patterns of LRF analysis after ablative 5-fraction SBRT for PDAC. Although EC is not currently endorsed by published pancreas SBRT guidelines, our low LRF incidence especially involving the CA/SMA demonstrates that EC should be considered, even when delivering ablative dose. Furthermore, given that nearly all LRF were M or OOF we have considered expanding our institutional elective volumes. While the optimal EC dose is uncertain, 33-35 Gy appears effective in limiting IF LRF and therefore has been standardized within ongoing ablative SBRT trials for PDAC at our institution.

Ablative 5-Fraction CT vs. MR-Guided Pancreatic SBRT: Evaluation of Interfraction Anatomic Changes on Dosimetric Constraints

PURPOSE/OBJECTIVE(S)

CT-guided SBRT for locally advanced pancreatic cancer (LAPC) is usually non-ablative (BED < 100 Gy10) to minimize grade 3+ toxicity risks given the concern of interfraction anatomic changes (IACs) in GI anatomy and imaging quality associated with kV-CBCT. Emerging data demonstrate that MR guidance facilitates 5-fraction (fx) dose escalation due to superior soft tissue contrast, continuous intrafraction imaging, automatic beam gating, and on-table adaptive replanning capability. Treatment outcomes for ablative 5-fx CT- vs. MR-guided SBRT are not well characterized, nor are differences in predicted GI OAR doses when accounting for IACs.

MATERIALS/METHODS

Weevaluated 40 plans (20 CT, 20 MR) for 20 LAPC patients (pts) previously treated in breath hold (BH) on a 0.35 T MR-Linac. Prescribed dose was 50 Gy (gross disease) and 33 Gy (elective) in 5 fx using a simultaneous integrated boost technique. CT plans were retrospectively created using 2-3 VMAT arcs with the same prescription dose, target volumes (assuming BH), and constraints (prioritizing OARs over target coverage) as the MR IMRT plans (∼20-40 fields). CT planners were blinded to MR plans. We compared predicted GI OAR dose of CT vs. MR plans across each of the 5 fx for all 20 patients to evaluate the dosimetric impact of IACs by coregistering CT plans to the anatomy of the day based on 0.35T MR scans acquired for GI OAR segmentation and treatment delivery.

RESULTS

MedianV100% of the GTV, CTV, PTV50, and PTV33 across the original CT vs. MR plans were 97.5% vs. 91.3% (p = 0.017), 99.9% vs. 98.2% (p<0.01), 86.2% vs. 79.3% (p = 0.39), and 97.2% vs. 93.0% (p<0.01), respectively. GI OAR constraints were met for all original CT/MR plans although it was predicted that 1+ GI OAR constraint would be violated (most commonly duodenum) for 88/100 CT vs. 85/100 MR fractions. Across the 88 violated CT fractions, the median predicted GI OAR doses were duodenum V35: 3.3 cc (range: 0.16-18.0cc), duodenum V40: 1.2 cc (range: 0.01-11.9cc), small bowel V35: 1.2 cc (range: 0.4-10.9cc), small bowel V40: 0.2 cc (range: 0.04-7.0cc), stomach V35: 1.5 cc (range: 0.52-6.8cc), stomach V40: 0.3 cc (range: 0.05-2.8cc). GI OAR doses across the 85 violated MR fractions were similar. Median fxs per pt with 1+ predicted GI OAR violation was 5 (range: 1-5) for both CT and MR plans.

CONCLUSION

This isthe first evaluation of IAC effects on predicted GI OAR dose for 5-fx CT- vs. MR-guided SBRT. Although VMAT arcs facilitated higher target coverage in the initial CT plans, GI OAR constraint violations were observed in 85-88% of CT/MR plans. Although on-table adaptive replanning is routine on MR-guided Linacs it is not commonly available on CT-guided Linacs. As such, ablative 5-fx SBRT delivered with CT guidance is expected to result in significant toxicity due to exceeding GI OAR constraints for most delivered fractions.

Single-fraction radiosurgery outcomes for large vestibular schwannomas in the upfront or post-surgical setting: a systematic review and International Stereotactic Radiosurgery Society (ISRS) Practice Guidelines

PURPOSE

To perform a systematic review of literature specific to single-fraction stereotactic radiosurgery (SRS) for large vestibular schwannomas (VS), maximum diameter ≥ 2.5 cm and/or classified as Koos Grade IV, and to present consensus recommendations on behalf of the International Stereotactic Radiosurgery Society (ISRS).

METHODS

The Medline and Embase databases were used to apply the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) approach. We considered eligible prospective and retrospective studies, written in the English language, reporting treatment outcomes for large VS; SRS for large post-operative tumors were analyzed in aggregate and separately.

RESULTS

19 of the 229 studies initially identified met the final inclusion criteria. Overall crude rate of tumor control was 89% (93.7% with no prior surgery vs 87.7% with prior surgery). Rates of salvage microsurgical resection, need for shunt, and additional SRS in all series versus those with no prior surgery were 9.6% vs 3.3%, 4.7% vs 6.4% and 1% vs 0.9%, respectively. Rates of facial palsy and hearing preservation in all series versus those with no prior surgery were 1.3% vs 3.4% and 34.2% vs 40.4%, respectively.

CONCLUSIONS

Upfront SRS resulted in high rates of tumor control with acceptable rates of facial palsy and hearing preservation as compared to the results in those series including patients with prior surgery (level C evidence). Therefore, although large VS are considered classic indication for microsurgical resection, upfront SRS can be considered in selected patients and we recommend a prescribed marginal dose from 11 to 13 Gy (level C evidence).

Characterization of Large Brain Metastases with 18F-Fluciclovine PET/CT Treated with Staged Stereotactic Radiosurgery (SSRS): Phase 1 Proof-of-Concept Interim Analysis

PURPOSE/OBJECTIVE(S)

Single-session stereotactic radiosurgery (SRS) for large brain metastases (>2cm) results in modest local control. Temporally staged SRS (SSRS), whereby 2 stages of SRS are delivered over a time interval of several weeks, is a novel strategy associated with improved control rates and acceptable radiation necrosis rates. Biomarkers for response are lacking. Here, we report interim results of a phase 1, proof-of-concept study (NCT04689048) to assess the potential clinical utility of amino acid radiotracer 18F-fluciclovine PET/CT as a functional integral biomarker for patients with large brain metastases treated with SSRS.

MATERIALS/METHODS

Patients with previously untreated large brain metastases (≥1 lesion; >2cm) underwent a baseline (pre-treatment) 18F-fluciclovine PET/CT and contrast-enhanced treatment planning brain MRI immediately before first SSRS (15 Gy), an interim PET/CT + MRI (4 weeks after the 1st SSRS, immediately prior the 2nd SSRS [15 Gy]), and post-treatment PET/CT + MRI (8 weeks after 2nd SSRS). This interim analysis reviewed the imaging characteristics from static PET images acquired 10-25 minutes after 18F-fluciclovine injection, for the first 7 enrolled patients who completed baseline imaging and 5 who completed the entire treatment course.

RESULTS

Seven patients completed baseline imaging and were treated with SSRS for 9 protocol-eligible target lesions, and an additional 25 bystander lesions were treated with SRS. The median age was 72 years and 57% were female. All lesions > 5 mm exhibited baseline increased 18F-fluciclovine uptake compared to the normal contralateral brain. The median baseline target lesion diameters and volumes were 2.16 cm (1.76-3.22 cm) and 4.71cc (2.24-10.21 cc). The median baseline SUVmax, SUVpeak, and SUVmean values were 5.78 (2.16-8.79), 3.33 (0.5-2.72), and 1.75 (1.22-5.16), respectively. The median relative reduction in diameter and volume were both 2% (-13% to 23% and -30% to 60%, respectively) at the interim scans, and at the first follow-up were 30% (-0.2% to 44%) and 43% (-13% to 94%), respectively. Corresponding median relative reduction values for SUVmax, SUVpeak, and SUVmean at interim scans were 20% (-174%-73%), 9% (-99% to 75%), and 14% (-36% to 69%), and at first follow-up 59% (21% to 87%), 41% (-11% to 86%), and 21% (-44% to 79%), respectively. Bystander lesions (< 2 cm) treated with SRS had a median baseline lesion diameter and volume of 0.5 cm (Range: 0.20-1.64 cm) and 0.06 cc (Range: 0.01-1.94 cc). Corresponding median reductions for SUVmax were 5% at interim and 63% at follow-up scans.

CONCLUSION

This proof-of-concept interim study reports baseline 18F-fluciclovine metrics for patients with brain metastases of varying lesion diameters and volumes. Target lesions appear to demonstrate interval reduction in PET metrics after SSRS, more than dimensional measurements alone.

Tumor Treating Fields therapy with standard systemic therapy versus standard systemic therapy alone in metastatic non-small-cell lung cancer following progression on or after platinum-based therapy (LUNAR): a randomised, open-label, pivotal phase 3 study

BACKGROUND

Tumor Treating Fields (TTFields) are electric fields that disrupt processes critical for cancer cell survival, leading to immunogenic cell death and enhanced antitumour immune response. In preclinical models of non-small-cell lung cancer, TTFields amplified the effects of chemotherapy and immune checkpoint inhibitors. We report primary results from a pivotal study of TTFields therapy in metastatic non-small-cell lung cancer.

METHODS

This randomised, open-label, pivotal phase 3 study recruited patients at 130 sites in 19 countries. Participants were aged 22 years or older with metastatic non-small-cell lung cancer progressing on or after platinum-based therapy, with squamous or non-squamous histology and ECOG performance status of 2 or less. Previous platinum-based therapy was required, but no restriction was placed on the number or type of previous lines of systemic therapy. Participants were randomly assigned (1:1) to TTFields therapy and standard systemic therapy (investigator's choice of immune checkpoint inhibitor [nivolumab, pembrolizumab, or atezolizumab] or docetaxel) or standard therapy alone. Randomisation was performed centrally using variable blocked randomisation and an interactive voice-web response system, and was stratified by tumour histology, treatment, and region. Systemic therapies were dosed according to local practice guidelines. TTFields therapy (150 kHz) was delivered continuously to the thoracic region with the recommendation to achieve an average of at least 18 h/day device usage. The primary endpoint was overall survival in the intention-to-treat population. The safety population included all patients who received any study therapy and were analysed according to the actual treatment received. The study is registered with ClinicalTrials.gov, NCT02973789.

FINDINGS

Between Feb 13, 2017, and Nov 19, 2021, 276 patients were enrolled and randomly assigned to receive TTFields therapy with standard therapy (n=137) or standard therapy alone (n=139). The median age was 64 years (IQR 59-70), 178 (64%) were male and 98 (36%) were female, 156 (57%) had non-squamous non-small-cell lung cancer, and 87 (32%) had received a previous immune checkpoint inhibitor. Median follow-up was 10·6 months (IQR 6·1-33·7) for patients receiving TTFields therapy with standard therapy, and 9·5 months (0·1-32·1) for patients receiving standard therapy. Overall survival was significantly longer with TTFields therapy and standard therapy than with standard therapy alone (median 13·2 months [95% CI 10·3-15·5] vs 9·9 months [8·1-11·5]; hazard ratio [HR] 0·74 [95% CI 0·56-0·98]; p=0·035). In the safety population (n=267), serious adverse events of any cause were reported in 70 (53%) of 133 patients receiving TTFields therapy plus standard therapy and 51 (38%) of 134 patients receiving standard therapy alone. The most frequent grade 3-4 adverse events were leukopenia (37 [14%] of 267), pneumonia (28 [10%]), and anaemia (21 [8%]). TTFields therapy-related adverse events were reported in 95 (71%) of 133 patients; these were mostly (81 [85%]) grade 1-2 skin and subcutaneous tissue disorders. There were three deaths related to standard therapy (two due to infections and one due to pulmonary haemorrhage) and no deaths related to TTFields therapy.

INTERPRETATION

TTFields therapy added to standard therapy significantly improved overall survival compared with standard therapy alone in metastatic non-small-cell lung cancer after progression on platinum-based therapy without exacerbating systemic toxicities. These data suggest that TTFields therapy is efficacious in metastatic non-small-cell lung cancer and should be considered as a treatment option to manage the disease in this setting.

FUNDING

Novocure.

National Cancer Institute Collaborative Workshop on Shaping the Landscape of Brain Metastases Research: challenges and recommended priorities

Brain metastases are an increasing global public health concern, even as survival rates improve for patients with metastatic disease. Both metastases and the sequelae of their treatment are key determinants of the inter-related priorities of patient survival, function, and quality of life, mandating a multidimensional approach to clinical care and research. At a virtual National Cancer Institute Workshop in September, 2022, key stakeholders convened to define research priorities to address the crucial areas of unmet need for patients with brain metastases to achieve meaningful advances in patient outcomes. This Policy Review outlines existing knowledge gaps, collaborative opportunities, and specific recommendations regarding consensus priorities and future directions in brain metastases research. Achieving major advances in research will require enhanced coordination between the ongoing efforts of individual organisations and consortia. Importantly, the continual and active engagement of patients and patient advocates will be necessary to ensure that the directionality of all efforts reflects what is most meaningful in the context of patient care.

Stereotactic Body Radiotherapy for Lung Oligo-metastases: Systematic Review and International Stereotactic Radiosurgery Society Practice Guidelines

PURPOSE

A systematic review of treatment characteristics, outcomes, and treatment-related toxicities of stereotactic body radiation therapy (SBRT) for pulmonary oligometastases served as the basis for development of this International Stereotactic Radiosurgery Society (ISRS) practice guideline.

METHODS

In accordance with PRISMA guidelines, a systematic review was performed of retrospective series with ≥50 patients/lung metastases, prospective trials with ≥25 patients/lung metastases, analyses of specific high-risk situations, and all randomized trials published between 2012 and July 2022 in the MEDLINE or Embase database using the key words "lung oligometastases", "lung metastases", "pulmonary metastases", "pulmonary oligometastases", "stereotactic body radiation therapy (SBRT)" and "stereotactic ablative body radiotherapy (SBRT)". Weighted random effects models were used to calculate pooled outcomes estimates.

RESULTS

Of the 1884 articles screened, 35 analyses (27 retrospective-, 5 prospective, and 3 randomized trials) reporting on treatment of >3600 patients and >4650 metastases were included. The median local control was 90 % (Range: 57-100 %) at 1 year and 79 % (R: 70-96 %) at 5 years. Acute toxicity ≥3 was reported for 0.5 % and late toxicity ≥3 for 1.8 % of patients. A total of 21 practice recommendations covering the areas of staging & patient selection (n = 10), SBRT treatment (n = 10), and follow-up (n = 1) were developed, with agreements rates of 100 %, except for recommendation 13 (83 %).

CONCLUSION

SBRT represents an effective definitive local treatment modality combining high local control rates with low risk of radiation-induced toxicities.

Stereotactic body radiotherapy for Ultra-Central lung Tumors: A systematic review and Meta-Analysis and International Stereotactic Radiosurgery Society practice guidelines

BACKGROUND

Stereotactic body radiotherapy (SBRT) is an effective and safe modality for early-stage lung cancer and lung metastases. However, tumors in an ultra-central location pose unique safety considerations. We performed a systematic review and meta-analysis to summarize the current safety and efficacy data and provide practice recommendations on behalf of the International Stereotactic Radiosurgery Society (ISRS).

METHODS

We performed a systematic review using PubMed and EMBASE databases of patients with ultra-central lung tumors treated with SBRT. Studies reporting local control (LC) and/or toxicity were included. Studies with <5 treated lesions, non-English language, re-irradiation, nodal tumors, or mixed outcomes in which ultra-central tumors could not be discerned were excluded. Random-effects meta-analysis was performed for studies reporting relevant endpoints. Meta-regression was conducted to determine the effect of various covariates on the primary outcomes.

RESULTS

602 unique studies were identified of which 27 (one prospective observational, the remainder retrospective) were included, representing 1183 treated targets. All studies defined ultra-central as the planning target volume (PTV) overlapping the proximal bronchial tree (PBT). The most common dose fractionations were 50 Gy/5, 60 Gy/8, and 60 Gy/12 fractions. The pooled 1- and 2-year LC estimates were 92 % and 89 %, respectively. Meta-regression identified biological effective dose (BED10) as a significant predictor of 1-year LC. A total of 109 grade 3-4 toxicity events, with a pooled incidence of 6 %, were reported, most commonly pneumonitis. There were 73 treatment related deaths, with a pooled incidence of 4 %, with the most common being hemoptysis. Anticoagulation, interstitial lung disease, endobronchial tumor, and concomitant targeted therapies were observed risk factors for fatal toxicity events.

CONCLUSION

SBRT for ultra-central lung tumors results in acceptable rates of local control, albeit with risks of severe toxicity. Caution should be taken for appropriate patient selection, consideration of concomitant therapies, and radiotherapy plan design.

Accelerated hypofractionated magnetic resonance-guided adaptive radiotherapy for oligoprogressive non-small cell lung cancer

Given the positive results from recent randomized controlled trials in patients with oligometastatic, oligoprogressive, or oligoresidual disease, the role of radiotherapy has expanded in patients with metastatic non-small cell lung cancer (NSCLC). While small metastatic lesions are commonly treated with stereotactic body radiotherapy (SBRT), treatment of the primary tumor and involved regional lymph nodes may require prolonged fractionation schedules to ensure safety especially when treating larger volumes in proximity to critical organs-at-risk (OARs). We have developed an institutional MR-guided adaptive radiotherapy (MRgRT) workflow for these patients. We present a 71-year-old patient with stage IV NSCLC with oligoprogression of the primary tumor and associated regional lymph nodes in which MR-guided, online adaptive radiotherapy was performed, prescribing 60 Gy in 15 fractions. We describe our workflow, dosimetric constraints, and daily dosimetric comparisons for the critical OARs (esophagus, trachea, and proximal bronchial tree [PBT] maximum doses [D0.03cc]), in comparison to the original treatment plan recalculated on the anatomy of the day (i.e., predicted doses). During MRgRT, few fractions met the original dosimetric objectives: 6.6% for esophagus, 6.6% for PBT, and 6.6% for trachea. Online adaptive radiotherapy reduced the cumulative doses to the structures by 11.34%, 4.2%, and 5.62% when comparing predicted plan summations to the final delivered summation. Therefore, this case study presets a workflow and treatment paradigm for accelerated hypofractionated MRgRT due to the significant variations in daily dose to the central thoracic OARs to reduce treatment-related toxicity associated with radiotherapy.

Multi-Institutional Patterns of Use of Tumor-Treating Fields for Patients with Malignant Pleural Mesothelioma

(1) Background: The objective of this analysis was to evaluate the device usage rates and patterns of use regarding Tumor-Treating Fields (TTFields) for patients with malignant pleural mesothelioma (MPM) throughout the US. (2) Methods: We evaluated de-identified data from 33 patients with MPM enrolled in FDA-required HDE protocols at 14 institutions across the US from September 2019 to March 2022. (3) Results: The median number of total TTFields usage days was 72 (range: 6-649 days), and the total treatment duration was 160 months for all patients. A low usage rate (defined as less than 6 h per day, 25%) was observed in 34 (21.2%) months. The median TTFields usage in the first 3 months was 12 h per day (range: 1.9-21.6 h), representing 50% (range: 8-90%) of the potential daily duration. The median TTFields usage after 3 months decreased to 9.1 h per day (range: 3.1-17 h), representing 38% (range: 13-71%) of the daily duration, and was lower than usage in the first 3 months (p = 0.01). (4) Conclusions: This study represents the first multicenter analysis of real-world TTFields usage based on usage patterns for MPM patients in clinical practice. The real-world usage level was lower than the suggested daily usage. Further initiatives and guidelines should be developed to evaluate the impact of this finding on tumor control.

Treatment of glioblastoma using MRIdian® A3i BrainTx™: Imaging and treatment workflow demonstration

For patients with newly diagnosed glioblastoma, the current standard-of-care includes maximal safe resection, followed by concurrent chemoradiotherapy and adjuvant temozolomide, with tumor treating fields. Traditionally, diagnostic imaging is performed pre- and post-resection, without additional dedicated longitudinal imaging to evaluate tumor volumes or other treatment-related changes. However, the recent introduction of MR-guided radiotherapy using the ViewRay MRIdian A3i system includes a dedicated BrainTx package to facilitate the treatment of intracranial tumors and provides daily MR images. We present the first reported case of a glioblastoma imaged and treated using this workflow. In this case, a 67-year-old woman underwent adjuvant chemoradiotherapy after gross total resection of a left frontal glioblastoma. The radiotherapy treatment plan consisted of a traditional two-phase design (46 Gy followed by a sequential boost to a total dose of 60 Gy at 2 Gy/fraction). The treatment planning process, institutional workflow, treatment imaging, treatment timelines, and target volume changes visualized during treatment are presented. This case example using our institutional A3i system workflow successfully allows for imaging and treatment of primary brain tumors and has the potential for margin reduction, detection of early disease progression, or to detect the need for dose adaptation due to interfraction tumor volume changes.

OptImal Gamma kNife lIghTnIng sOlutioN (IGNITION) score to characterize the solution space of the Gamma Knife FIP optimizer for stereotactic radiosurgery

OBJECTIVES

The objective of this study is to evaluate the user-defined optimization settings in the Fast Inverse Planning (FIP) optimizer in Leksell GammaPlan® and determine the parameters that result in the best stereotactic radiosurgery (SRS) plan quality for brain metastases, benign tumors, and arteriovenous malformations (AVMs).

METHODS

Thirty patients with metastases and 30 with benign lesions-vestibular schwannoma, AVMs, pituitary adenoma, and meningioma-treated with SRS were evaluated. Each target was planned by varying the low dose (LD) and beam-on-time (BOT) penalties in increments of 0.1, from 0 to 1. The following plan quality metrics were recorded for each plan: Paddick conformity index (PCI), gradient index (GI), BOT, and maximum organ-at-risk (OAR) doses. A novel objective score matrix was calculated for each target using a linearly weighted combination of the aforementioned metrics. A histogram of optimal solutions containing the five best scores was extracted.

RESULTS

A total of 7260 plans were analyzed with 121 plans per patient for the range of LD/BOT penalties. The ranges of PCI, GI, and BOT across all metastatic lesions were 0.58-0.97, 2.1-3.8, and 8.8-238 min, respectively, and were 0.13-0.97, 2.1-3.8, and 8.8-238 min, respectively, for benign lesions. The objective score matrix showed unique optimal solutions for metastatic lesions and benign lesions. Additionally, the plan metrics of the optimal solutions were significantly improved compared to the clinical plans for metastatic lesions with equivalent metrics for all other cases.

CONCLUSION

In this study, FIP optimizer was evaluated to determine the optimal solution space to maximize PCI and minimize GI, BOT and OAR doses simultaneously for single metastatic/benign/non-neoplastic targets. The optimal solution chart was determined using a novel objective score which provides novice and expert planners a roadmap to generate the most optimal plans efficiently using FIP.

Proton Radiosurgery: Current Concepts and Limitations for CNS Radiosurgery

Introduction

Stereotactic radiosurgery (SRS) is highly conformal, high-dose radiation therapy delivered in 1-5 fractions, and is considered the standard of care for several central nervous system (CNS) indications. Particle therapies, such as protons, have physical and dosimetric advantageous properties compared to photons. However, proton SRS (PSRS) is not widely performed given the few particle therapy facilities, high-cost, and limited outcomes research as a sole modality and in comparative studies. The data available differs from each pathology. For AVMs, especially those with deep or eloquent locations, PSRS obliteration rates outcomes appear favorable and superior. For meningiomas, PSRS has been used for grade 1 alone, and for higher grades a PSRS boost has been considered. For vestibular schwannoma, PSRS seems to have favorable control rates with modest toxicity outcomes. For pituitary tumors, data shows excellent results with PSRS for functional and non-functioning adenomas. For brain metastasis, moderate doses of PSRS achieves high local control rates with low rates of radiation necrosis. For uveal melanoma, dedicated eyeline PSRS (4-5 fractions) are associated with very high tumor control and eye retention rates.

Conclusions

PSRS is effective and safe for various intracranial pathologies. Limited data, usually retrospective and single institution series exist. There are numerous advantages of protons over photons, so it is important to understand limitations with further studies. Published clinical outcomes and widespread adoption of proton therapy will be key to unlocking the potential benefits of PSRS.

Racial disparities in clinical presentation, surgical procedures, and hospital outcomes among patients with hepatocellular carcinoma in the United States

BACKGROUND

Hepatocellular carcinoma (HCC) is one of the leading causes of cancer-related deaths in the United States (US), with substantial disparities observed in cancer incidence and survival among racial groups. This study provides analyses on race and ethnicity disparities for patients with HCC.

METHODS

This is a cross-sectional analysis of data from the National Inpatient Sample (NIS) between 2011 and 2016, utilizing the STROBE guidelines. Multivariate logistic regression analyses were used to examine the risk-adjusted associations between race and pre-treatment clinical presentation, surgical procedure allocation, and post-treatment hospital outcomes. All clinical parameters were identified using ICD-9-CM and ICD-10-CM diagnosis and procedure codes.

RESULTS

83,876 weighted HCC hospitalizations were reported during the study period. Patient demographics were divided according to NIS racial/ethnic categorization, which includes Caucasian (57.3%), African American (16.9%), Hispanic (15.7%), Asian or Pacific Islanders (9.3%), and Native American (0.8%). Association between greater odds of hospitalization and Elixhauser Comorbidity Index > 4 was significantly higher among Native Americans (aOR=1.79; 95% CI: 1.23-2.73), African Americans (aOR=1.24; 95% CI: 1.12-1.38), and Hispanics (aOR=1.11; 95% CI, 1.01-1.24). Risk-adjusted association between race and receipt of surgical procedures demonstrated that the odds of having surgery was significantly lower for African Americans (aOR=0.64; 95% CI: 0.55-0.73) and Hispanics (aOR=0.70; 95% CI: 0.59-0.82), while significantly higher for Asians/Pacific Islanders (aOR=1.36; 95% CI: 1.28-1.63). Post-operative complications were significantly lower for African Americans (aOR=0.68; 95% CI: 0.55-0.86) while the odds of in-hospital mortality were significantly higher for African Americans (aOR=1.28; 95% CI: 1.11-1.49) and Asians/Pacific Islanders (aOR=1.26; 95% CI: 1.13-1.62).

CONCLUSIONS

After controlling for potential confounders, there were significant racial disparities in pre-treatment presentations, surgical procedure allocations, and post-treatment outcomes among patients with HCC. Further studies are needed to determine the underlying factors for these disparities to develop targeted interventions to reduce these disparities of care.

Key Clinical Principles in the Management of Glioblastoma

Glioblastoma is the most common and aggressive primary brain tumor in the adult population and leads to considerable morbidity and mortality. It has a dismal prognosis with average survival of 15-18 months, and the current standard-of-care treatment paradigm includes maximal surgical resection and postoperative concurrent chemoradiotherapy and maintenance chemotherapy, with consideration of Tumor Treating Fields. There is a major emphasis to enroll patients onto ongoing clinical trials to further improve treatment outcomes, given the aggressive nature of the disease course and poor patient survival. Recent research efforts have focused on radiotherapy dose intensification, regulation of the tumor microenvironment, and exploration of immunotherapeutic approaches to overcome the barriers to treatment. This review article outlines the current evidence-based management principles as well as reviews recent clinical trial data and ongoing clinical studies evaluating novel therapeutic options.

Initial clinical experience with magnetic resonance-guided radiotherapy in pediatric patients: Lessons learned from a single institution with proton therapy

Purpose/Objectives

Magnetic resonance-guided radiotherapy (MRgRT) is increasingly used in a variety of adult cancers. To date, published experience regarding the use of MRgRT in pediatric patients is limited to two case reports. We report on the use of MRgRT for pediatric patients at our institution during a four-year period and describe important considerations in the selection and application of this technology in children.

Materials/Methods

All patients treated with MRgRT since inception at our institution between 4/2018 and 4/2022 were retrospectively reviewed. We also evaluated all pediatric patients treated at our institution during the same period who received either imaging or treatment using our magnetic resonance-guided linear accelerator (MR Linac). We summarize four clinical cases where MRgRT was selected for treatment in our clinic, including disease outcomes and toxicities and describe our experience using the MR Linac for imaging before and during treatment for image fusion and tumor assessments.

Results

Between 4/2018 and 4/2022, 535 patients received MRgRT at our center, including 405 (75.7%) with stereotactic ablative radiotherapy (SABR). During this period, 347 distinct radiotherapy courses were delivered to pediatric patients, including 217 (62.5%) with proton therapy. Four pediatric patients received MRgRT. One received SABR for lung metastasis with daily adaptive replanning and a second was treated for liver metastasis using a non-adaptive workflow. Two patients received fractionated MRgRT for an ALK-rearranged non-small cell lung cancer and neuroblastoma. No Grade 2 or higher toxicities were observed or reported during MRgRT or subsequent follow-up. Twelve patients underwent MR imaging without contrast during treatment for brain tumors to assess for tumor/cystic changes. Two patients treated with other modalities underwent MR simulation for target volume delineation and organ at risk sparing due to anatomic changes during treatment or unexpected delays in obtaining diagnostic MR appointments.

Conclusions

In four pediatric patients treated with MRgRT, treatment was well tolerated with no severe acute effects. At our center, most pediatric patients are treated with proton therapy, but the cases selected for MRgRT demonstrated significant organ at risk sparing compared to alternative modalities. In particular, MRgRT may provide advantages for thoracic/abdominal/pelvic targets using gated delivery and adaptive replanning, but selected patients treated with fractionated radiotherapy may also benefit MRgRT through superior organ at risk sparing.

Expert guidance on prophylaxis and treatment of dermatologic adverse events with Tumor Treating Fields (TTFields) therapy in the thoracic region

Tumor Treating Fields (TTFields) are electric fields, delivered via wearable arrays placed on or near the tumor site, that exert physical forces to disrupt cellular processes critical for cancer cell viability and tumor progression. As a first-in-class treatment, TTFields therapy is approved for use in newly diagnosed glioblastoma, recurrent glioblastoma, and pleural mesothelioma. Additionally, TTFields therapy is being investigated in non-small cell lung cancer (NSCLC), brain metastases from NSCLC, pancreatic cancer, ovarian cancer, hepatocellular carcinoma, and gastric adenocarcinoma. Because TTFields therapy is well tolerated and delivery is locoregional, there is low risk of additive systemic adverse events (AEs) when used with other cancer treatment modalities. The most common AE associated with TTFields therapy is mild-to-moderate skin events, which can be treated with topical agents and may be managed without significant treatment interruptions. Currently, there are no guidelines for oncologists regarding the management of TTFields therapy-related skin AEs in the thoracic region, applicable for patients with pleural mesothelioma or NSCLC. This publication aims to provide guidance on preventing, minimizing, and managing dermatologic AEs in the thoracic region to help improve patient quality of life and reduce treatment interruptions that may impact outcomes with TTFields therapy.