Mangum, Ross

Abstract Response Assessment in Pediatric Neuro-Oncology (RAPNO) is an international working group dedicated to developing standardized recommendations for response assessment in children with central nervous system tumors enrolled on clinical trials. This standardization facilitates easier and more reliable comparison of responses across trials. Since the first RAPNO publication in 2013, response guidelines have been issued for medulloblastoma (MB), low-grade glioma (LGG), high-grade glioma (HGG), diffuse intrinsic pontine glioma, ependymoma, and craniopharyngioma. Many of these guidelines have already been incorporated into clinical trials to evaluate their effectiveness and accuracy. RAPNO has always been predicated on the idea that these consensus recommendations will require updates over time as they are applied in practice given technological advancements, evolving treatment approaches, and growing knowledge of disease pathology. A half-day RAPNO symposium sponsored by the Society of Neuro-Oncology was held in San Diego, California, United States, on May 15, 2025. This event coincided with the 8th Biennial Pediatric Society of Neuro-Oncology meeting. The main objectives were to identify ongoing RAPNO challenges, discuss potential updates, and plan future initiatives across 3 specific groups: (1) LGG/Craniopharyngioma, (2) HGG/diffuse midline glioma (DMG)/Ependymoma, and (3) MB and other seeding tumors. This manuscript reviews the symposium proceedings and highlights key topics and challenges discussed, as well as outlining future RAPNO initiatives.

Malignant transformation of intracranial nongerminomatous germ cell tumors (NGGCTs) is a rare but clinically relevant phenomenon. We present the case of a 13-year-old boy with a localized, pineal NGGCT. After an initial favorable response, tumor growth was noted while still on chemotherapy. Histopathologic characterization revealed that 40% of the tumor was embryonal rhabdomyosarcoma (RMS), consistent with potential malignant transformation. Due to the rare nature of NGGCT malignant transformation, the best clinical approach to these cases remains unclear. We explore existing cases, treatments, and outcomes of malignant transformation in intracranial NGGCTs to help inform future clinical decision-making and the establishment of treatment guidelines.

We present the case of a 12-year-old female who presented with progressive back pain and was found to have a localized mass in the lumbar spine. The resected tissue was characterized by epithelioid cells with a papillary appearance and high mitotic activity. Initial immunohistochemical analysis was consistent with a diagnosis of atypical meningioma. However, comprehensive molecular profiling detected a CRTC1::NCOA2 fusion with a novel NCOA2 gene rearrangement, leading to a revised descriptive diagnosis of epithelioid mesenchymal neoplasm with CRTC1::NCOA2 fusion. This specific fusion has only been reported in 2 other cases involving mesenchymal neoplasms of the palate and urinary bladder. While CRTC1 is frequently associated with MAML2 fusion in mucoepidermoid carcinomas, NCOA2 rearrangements occur in a variety of solid and hematologic malignancies. There is a paucity of information on the prognostic relevance of these fusion partners. This is the first reported case of a CRTC1::NCOA2 fusion in a pediatric patient with a spinal cord malignancy. The mechanistic significance and prognostic implications of this fusion will be discussed.

Atypical teratoid/rhabdoid tumor (ATRT) is an aggressive, malignant embryonal tumor with dismal long-term survival despite aggressive multimodal therapy. While this tumor typically presents in infancy or early childhood, there are published case reports of adult-onset ATRT. Making prognostic conclusions or therapeutic decisions for this older patient population remains challenging due to the paucity of these reports. A 25-year-old female with Down syndrome presented with dysphagia and facial droop and was found to have an avidly enhancing, cerebellopontine angle mass. Histology demonstrated sheets of rhabdoid cells with loss of INI1 expression, pathognomonic for ATRT. Further sequencing detected a frameshift SMARCB1 mutation and methylation profiling matched with high confidence to the MYC subclass of ATRT. The patient was treated with subtotal surgical resection and focal proton beam irradiation, followed by chemotherapy on a modified regimen due to concern for heightened risk of treatment-related toxicity. On most recent follow-up 22 months from diagnosis, the patient remains without evidence of disease. This report represents the first known case of ATRT in a young adult patient with Down syndrome, offering unique mechanistic insight into the tumorigenesis of ATRT. Further studies are needed to define an appropriate risk-adapted and standardized therapeutic approach for this patient population.

Abstract BACKGROUND Non-germinomatous germ cell tumors (NGGCT) constitute 35%- 45% of intracranial germ cell tumors. Growing teratoma syndrome has been observed in patients with NGGCTs after starting chemotherapy. While growing teratomas are typically benign, this process can rarely involve malignant transformation and result in poor prognosis. We present the case of a patient with pineal NGGCT and growing teratoma syndrome with malignant transformation to embryonal rhabdomyosarcoma. CASE REPORT A 13-year-old male presented with headaches and vision changes. An MRI brain demonstrated a 26 x 25 x 19 mm (AP X TR X CC) mixed solid and cystic pineal mass with no evidence of metastatic disease. Due to elevated alpha fetoprotein levels in the serum and cerebrospinal fluid, he was diagnosed with intracranial NGGCT. Treatment was initiated with alternating cycles of Carboplatin/Etoposide and Ifosfamide/Etoposide. After 2 cycles of chemotherapy, a complete biochemical response was noted but MRI showed increased tumor size (presumed growing teratoma syndrome). The patient underwent complete tumor resection. Histology showed embryonal rhabdomyosarcoma as a somatic malignancy arising in a mature teratoma. Further molecular characterization revealed somatic NF1 and KRAS pathogenic mutations that are consistent with the primary diagnosis. Methylation profiling, however, did not exhibit a match with any known malignancies. Continued complete response was noted following two additional chemotherapy cycles. The patient is planned for six total chemotherapy cycles followed by high-dose craniospinal radiation with boost to the primary tumor. CONCLUSIONS Malignant transformation is a rare phenomenon in NGGCT. There is no standard of care for these patients. Further studies are needed to define ideal therapy for this patient population.

Abstract BACKGROUND Atypical teratoid/rhabdoid tumor (ATRT) is a malignant, highly aggressive embryonal tumor of the central nervous system. Long-term survival remains dismal despite aggressive multimodal therapy, including a maximal safe surgical resection and intensive systemic chemotherapy +/- radiation therapy. While these tumors typically present in infancy or early childhood, there are scattered case reports of adult-onset ATRT. Making prognostic conclusions or therapeutic decisions for this older patient population remains challenging due to the paucity of these reports. CASE REPORT A 25-year-old female with Down syndrome presented with nausea, vomiting, dysphagia, and facial droop and was found to have an avidly enhancing, left cerebellopontine angle mass. There was initial clinical suspicion for leukemic chloroma given the patient’s Down syndrome status and known association with higher rates of hematologic malignancy concurrent with a dramatic scarcity of solid tumors in the Down syndrome population. However, histology demonstrated sheets of high-grade rhabdoid cells with loss of INI1 expression, pathognomonic for ATRT. Further sequencing defined a frameshift mutation in SMARCB1 (p.C298), and methylation profiling matched with high confidence to the MYC subclass of ATRT. The patient was treated with subtotal surgical resection and focal proton radiation, followed by chemotherapy on a modified regimen based on the Children’s Oncology Group protocol, ACNS0333. Systemic methotrexate and all consolidative high-dose chemotherapy with stem cell rescue were omitted due to concern for heightened risk of treatment-related toxicity. The patient remains alive and clinically asymptomatic 19 months from diagnosis. CONCLUSION This report represents the first known case of ATRT in an adult patient with Down syndrome, offering unique mechanistic insight into the tumorigenesis of ATRT. Adult ATRT is a rare entity without standardized treatment or established prognostic understanding. Further studies are needed to define an appropriate risk-adapted therapeutic approach for this patient population.

AbstractBackgroundRenal medullary carcinoma (RMC) is a diagnostically challenging, aggressive primary renal malignancy associated with abysmal survival. Delays in diagnosis contribute to most patients having diffusely metastatic disease at the time of initial presentation.MethodsWe present the case of a 13‐year‐old African American male with sickle cell trait who presented with a renal mass and hematuria. Evaluation included imaging, fluid cultures, and cytologic assessment.ResultsPatient was diagnosed with RMC based on cytologic assessment of sub‐centimeter fluid collections aspirated from the left kidney at the time of cortical biopsy for suspected renal mass. The additional fluid aspiration in conjunction with renal biopsy was an atypical but crucial step in early diagnosis.ConclusionCytomorphologic evaluation of fluid biospecimens is not currently part of the standard work‐up for patients with renal masses but, when available, can provide crucial information that reduces time to diagnosis. Prompt symptom recognition and treatment initiation may improve patient outcomes.

Abstract Background Craniopharyngioma is a histologically benign tumor of the suprasellar region for which survival is excellent but quality of life is often poor secondary to functional deficits from tumor and treatment. Standard therapy consists of maximal safe resection with or without radiation therapy. Few prospective trials have been performed, and response assessment has not been standardized. Methods The Response Assessment in Pediatric Neuro-Oncology (RAPNO) committee devised consensus guidelines to assess craniopharyngioma response prospectively. Results Magnetic resonance imaging is the recommended radiologic modality for baseline and follow-up assessments. Radiologic response is defined by 2-dimensional measurements of both solid and cystic tumor components. In certain clinical contexts, response to solid and cystic disease may be differentially considered based on their unique natural histories and responses to treatment. Importantly, the committee incorporated functional endpoints related to neuro-endocrine and visual assessments into craniopharyngioma response definitions. In most circumstances, the cystic disease should be considered progressive only if growth is associated with acute, new-onset or progressive functional impairment. Conclusions Craniopharyngioma is a common pediatric central nervous system tumor for which standardized response parameters have not been defined. A RAPNO committee devised guidelines for craniopharyngioma assessment to uniformly define response in future prospective trials.

Abstract INTRODUCTION: Craniopharyngioma (CP) is a histologically benign tumor of the pituitary stalk that accounts for 4% of pediatric central nervous system (CNS) tumors. Given its location, CP often causes neuro-endocrine, hypothalamic, and vision dysfunction. Standard therapy consists of maximally safe resection +/- radiation therapy (RT). Medical management, including intra-cystic therapy, may have utility in certain contexts. Survival after CP is excellent, but quality of life is often poor secondary to functional deficits from the tumor and/or treatment. Few prospective CP trials have been performed, and response assessment has not been standardized. METHODS: The Response Assessment in Pediatric Neuro-Oncology (RAPNO) committee, formed of international experts in relevant subspecialties, devised consensus guidelines from published literature and/or expert opinion to assess CP response in prospective clinical trials. RESULTS: Magnetic resonance imaging (MRI) is the recommended radiological modality for baseline and follow-up CP assessment. Computed tomography can be useful for identification of calcification in the initial diagnostic work-up. The committee defined specific standard MRI-based sequences focused on comprehensive evaluation of the suprasellar space. Radiologic CP response is defined by two-dimensional measurements of both solid and cystic tumor components. Three-dimensional measurements are also encouraged in prospective trials. In certain clinical contexts, response of solid and cystic disease may be differentially considered based on their unique natural histories and responses to treatment (including transient cyst growth during or after RT). Importantly, the committee incorporated functional endpoints related to neuro-endocrine and visual assessments into CP response definitions. In most circumstances, cystic disease should be considered progressive only if growth is associated with acute, new-onset or progressive functional impairment. CONCLUSION: CP is a common pediatric CNS tumor for which standardized response parameters have not been defined. A RAPNO committee devised guidelines for baseline and longitudinal assessments of CP to uniformly define response in future prospective trials.