Prospective Clinical Feasibility Study for MRI-Only Brain Radiotherapy

ObjectivesMRI-only radiotherapy (RT) provides a workflow to decrease the geometric uncertainty introduced by the image registration process between MRI and CT data and to streamline the RT planning. Despite the recent availability of validated synthetic CT (sCT) methods for the head region, there are no clinical implementations reported for brain tumors. Based on a preceding validation study of sCT, this study aims to investigate MRI-only brain RT through a prospective clinical feasibility study with endpoints for dosimetry and patient setup.Material and MethodsTwenty-one glioma patients were included. MRI Dixon images were used to generate sCT images using a CE-marked deep learning-based software. RT treatment plans were generated based on MRI delineated anatomical structures and sCT for absorbed dose calculations. CT scans were acquired but strictly used for sCT quality assurance (QA). Prospective QA was performed prior to MRI-only treatment approval, comparing sCT and CT image characteristics and calculated dose distributions. Additional retrospective analysis of patient positioning and dose distribution gamma evaluation was performed.ResultsTwenty out of 21 patients were treated using the MRI-only workflow. A single patient was excluded due to an MRI artifact caused by a hemostatic substance injected near the target during surgery preceding radiotherapy. All other patients fulfilled the acceptance criteria. Dose deviations in target were within ±1% for all patients in the prospective analysis. Retrospective analysis yielded gamma pass rates (2%, 2 mm) above 99%. Patient positioning using CBCT images was within ± 1 mm for registrations with sCT compared to CT.ConclusionWe report a successful clinical study of MRI-only brain radiotherapy, conducted using both prospective and retrospective analysis. Synthetic CT images generated using the CE-marked deep learning-based software were clinically robust based on endpoints for dosimetry and patient positioning.

SMART Syndrome: A Case Report

Introduction: Stroke-like migraine attacks after radiation therapy (SMART) syndrome, is a late complication of brain radiotherapy. (1) Symptoms are commonly subacute in onset and involve migraine type of headache, seizures, focal neurologic deficits.(2) . MRI findings are usually unilateral and posterior predominant cortical-subcortical hyperintensity, swelling and prominent gyriform (cortical and leptomeningeal) gadolinum enhancement in the areas of brain that underwent irradiation with or without diffusion restriction.(1) There is no standard treatment protocol of SMART syndrome. Antiepileptics and corticosteroids are commonly used drugs.Case Report: A 65 years old woman diagnosed with breast cancer with brain metastases and treated with more than 50 Gy brain radiotherapy. A couple of months later patient presented with acute right sided weakness and numbness, episodic myoclonic jerking of the right arm and leg and gait instability. MRI and magnetic resonance angiography of the brain with gadolinium revealed left parietooccipital cortical diffusion restriction and accompanying dilatation of the left posterior cerebral artery as new findings. Computed tomography perfusion revealed increased perfussion in the affected area. The patient was diagnosed with SMART syndrome.Management & Outcome: The patient was treated with dexamethasone (16 mg/day) and anticonvulsant therapy. Myoclonic seizures had almost completely remitted. However, her cognitive impairment persisted, then the patient arrested because of aspiration a month later.Discussion: Besides confirming SMART syndrome, diagnostic investigations is also important to exclude other etiologies. Posterior reversible encephalopathy syndrome, post-ictal changes, meningoencephalitis and cerebrovascular diseases are radiological differential diagnosis which should be considered.(3) Proper and early diagnosis of SMART syndrome is significant to refrain unneccessary aggressive approaches and for appropriate treatment to prevent sequela lesions.

Managing Central Nervous System Spread of Lung Cancer: The State of the Art

Brain metastases (BrM) are common in both non–small-cell lung cancer and small-cell lung cancer. Substantial progress in BrM management has occurred in the past decade related to advances in both radiation and medical oncology. Recent and ongoing radiation trials have focused on increasing the candidacy for focal therapy of BrM with stereotactic radiosurgery; reducing the toxicity and improving patient selection for whole brain radiotherapy; and, in small-cell lung cancer, evaluating brain magnetic resonance imaging surveillance without prophylactic cranial irradiation, hippocampal avoidance in prophylactic cranial irradiation and whole brain radiotherapy, and the role of upfront stereotactic radiosurgery for BrM. In medical oncology, the development of multiple tyrosine kinase inhibitors with encouraging CNS activity and emerging data on the CNS activity of immune checkpoint inhibitors in some patients have opened the door to novel systemic and multidisciplinary treatment strategies for the management of BrM. Future research will focus on more robust characterizations of the CNS activity of targeted therapy and immunotherapies, as well as optimal integration and patient selection for multidisciplinary strategies involving CNS-active drugs, radiation therapy, and CNS surveillance.

Isolated Leptomeningeal Progression in a Patient with NTRK Fusion+ Uterine Sarcoma: A Case Report

While neurotrophic tropomyosin receptor kinase (NTRK) fusions represent rare oncogenic drivers (&#x3c;1% of solid cancers), the recent approval of NTRK inhibitors (larotrectinib and entrectinib) led to dramatic responses in patients with NTRK fusion+ tumors. Both drugs have phase I data, demonstrating efficacy in the central nervous system (CNS), including both primary brain tumors and brain metastases. We present a 29-year-old woman who was diagnosed with <i>NTRK3-SPECC1L</i> fusion+ undifferentiated uterine sarcoma and underwent resection, chemotherapy, and radiotherapy. Two years later, lung metastases were discovered. She was started on larotrectinib with complete response. She remained stable on larotrectinib until she presented with altered mental status and seizures. MRI demonstrated leptomeningeal enhancement, but because leptomeningeal progression from sarcoma is exceedingly rare and her symptoms improved dramatically with antiepileptics, these findings were initially attributed to seizures. After 2 unrevealing lumbar punctures and stable systemic imaging, a brain biopsy demonstrated metastatic sarcoma, still showing NTRK positivity. She underwent whole brain radiotherapy and was switched to entrectinib, but had clinical progression 1 month later and transitioned to hospice. This case demonstrates the efficacy of NTRK inhibitors in rare and aggressive cancer but highlights that these patients can develop isolated CNS progression even in the setting of CNS-penetrant drugs. CNS progression can occur if there is incomplete CNS drug penetration, discordance in molecular profiles between CNS and systemic disease, or acquired NTRK inhibitor resistance. In this case, CNS disease maintained the NTRK fusion status, but either inadequate CNS penetration or development of a resistance gene may explain the isolated CNS progression.

NQPC-5 Does high-dose methotrexate-based chemotherapy for relapsed primary CNS lymphoma increase a risk of leukoencephalopathy with prior whole brain radiotherapy?

Backgrounds: Standard care for primary central nervous system lymphoma (PCNSL) comprises high-dose (HD) methotrexate (MTX) -based chemotherapy with or without consolidation whole brain radiotherapy (WBRT). HD-MTX administration following WBRT has been suggested to increase a risk of leukoencephalopathy. However, given that there are no other agents with efficacy similar to or better than MTX, patients with relapsed PCNSL may often be treated with regimens containing HD-MTX if the initial MTX treatment achieved a long-term complete remission. Here, we retrospectively analyzed prevalence and an extent of white mater damages in association with prior WBRT in patients with relapsed PCNSL treated with HD-MTX based therapy. Patients & methods: Among 79 patients with relapsed/refractory PCNSL in a total of 162 patients with newly-diagnosed PCNSL treated in our institution from April, 2000 to February, 2021, 35 patients were identified with evaluable KPS, MMSE, and Fazekas scale data at both baseline and follow-up periods. Of the 35 patients, 22 were treated with chemotherapy at a relapse (10 with prior WBRT, while 12 without WBRT), and were included in this preliminary study. Results: In the WBRT group (male/female: 5/5), median age was 65 years (range, 45–73), initial median KPS was 70 (40–90), and median WBRT dose was 27 Gy (23.4–40). Median progression-free survival (mPFS) was 11.8 months, and median overall survival (mOS) was not reached. In the non-WBRT group (M/F 8/4), median age 75 (62–84), initial mKPS 80 (50–90), mPFS 16.2 m, and mOS not reached. Initial KPS and MMSE score tended to be worse in WBRT group, presumably due to enrichment of patients with poorer performance status and more comorbidities. A decline in the Fazekas score was not associated with MMSE deterioration.Conclusions: The preliminary analysis was not informative enough, and further extensive imaging analysis will be exploited.