Exoscopic microneurosurgery in pediatric brain tumors: an ideal tool for complex and peculiar anatomo-topographic scenarios?

PURPOSE: Since its introduction in the 1950s, the microsurgical paradigm has revolutionized neurosurgery. New technologies have been introduced over the years trying to overcome limits of the classical operating microscope. The recently developed 3D exoscopes represent a potential new paradigm for micro-neurosurgery. We analyzed our own experience with a 4 K-3D exoscope in a series of pediatric brain tumors to verify its advantages and limitations in comparison to the operating microscope and in light of the literature. METHODS: Twenty-five pediatric patients with brain tumors underwent surgery at our Institute; the population has been analyzed and described. A score to evaluate the exoscopes and compare it to the operating microscope was considered and postoperatively applied to each single case. RESULTS: The exoscope appears to be at least comparable to the operating microscope (OM) in all analyzed aspects. In the case of deep-seated or fourth ventricle tumors, the exoscope seems to be superior to the microscope. A surgeon-dependent learning curve is necessary for neurosurgeons to be confident with the exoscope. CONCLUSION: Exoscopes appear to be as safe and effective as operating microscopes in pediatric neuro-oncological surgery. They have some advantages that make them superior to microscopes, particularly regarding surgeon ergonomics and fatigue, visual field qualities, and higher choice of intraoperative viewing angles.

Association of area deprivation index (ADI) with demographics and postoperative outcomes in pediatric brain tumor patients.

PURPOSE: Although social determinants of health (SDOH) have been associated with adverse surgical outcomes, cumulative effects of multiple SDOH have never been studied. The area deprivation index (ADI) assesses cumulative impact of SDOH factors on outcomes. We analyzed the relationship between ADI percentile and postoperative outcomes in pediatric patients diagnosed with brain tumors. METHODS: A retrospective, observational study was conducted on our consecutive series of pediatric brain tumor patients presenting between January 1, 1999, and May 31, 2022. Demographics and outcomes were collected, identifying SDOH factors influencing outcomes found in the literature. ADI percentiles were identified based on patient addresses, and patients were stratified into more (ADI 0-72%) and less (ADI 73-100%) disadvantaged cohorts. Univariate and multivariate logistic regression analyses were completed for demographics and outcomes. RESULTS: A total of 272 patients were included. Demographics occurring frequently in the more disadvantaged group were Black race (13.1% vs. 2.8%; P = .003), public insurance (51.5% vs. 27.5%; P < .001), lower median household income ($64,689 ± $19,254 vs. $46,976 ± $13,751; P < .001), and higher WHO grade lesions (15[11.5%] grade III and 8[6.2%] grade IV vs. 8[5.6%] grade III and 5[3.5%] grade IV; P = .11). The more disadvantaged group required adjunctive chemotherapy (25.4% vs. 12.05%; P = .007) or radiation therapy (23.9% vs. 12.7%; P = .03) more frequently and had significantly greater odds of needing adjunctive chemotherapy (odds ratio [OR], 1.11; confidence interval [CI], 1.01-1.22; P = .03) in a multivariate model, which also identified higher WHO tumor grades at presentation (OR, 1.20; CI, 1.14-1.27; P < .001). CONCLUSION: These findings are promising for use of ADI to represent potential SDOH disadvantages that pediatric patients may face throughout treatment. Future studies should pursue large multicenter collaborations to validate these findings.

Role of sodium fluorescein in pediatric low-grade glioma surgery: an update.

PURPOSE: Complete surgical resection is still the mainstay in the treatment of central nervous system low-grade tumors, eventually resulting curative. The complete surgical removal of these lesions, however, may be difficult in some cases because of their infiltrative nature. Intraoperative adjuncts may be a game changer. Sodium fluorescein (SF) is among the ideal candidates as intraoperative tools to favor the actual recognition of the tumor extension, since it accumulates in areas of altered blood-brain barrier, a typical characteristic of pediatric gliomas, and has a low rate of adverse events. This work proposes an update of previous works about the evaluation of the feasibility and usefulness of a systematic use of SF in a low-grade lesion group of pediatric patients. METHODS: Pediatric patients operated on for a resection or a biopsy of a low-grade glial or glioneuronal lesion (WHO grade I and II) at our Institution between September 2021 and December 2023, with the intraoperative use of sodium fluorescein (SF), were enrolled in the study. We collected pre-operative and postoperative clinical and radiological data, intraoperative findings, and post-operative pathological diagnoses. RESULTS: No adverse events were registered related to the intraoperative use of SF. SF appeared useful for the localization of boundaries of tumors, especially when characterized by a high degree of infiltration or by a deep-seated location, and for the checking of possible tumor remnants at the end of surgery. A good tumor-to-healthy tissue contrast was registered when tumor visualization was in a range between 1 to 2 h and 30 min after SF injection. Possible "false positives" due to intraoperative vascular wall injury and clearance of SF from both tumor and healthy tissue were observed in some cases and still remain open issues. CONCLUSIONS: SF is a feasible and safe intraoperative adjunct tool in the surgical removal of pediatric low-grade tumors. SF may show its usefulness especially in selected cases, such as deep-seated lesions and infiltrating tumors. Its safety profile, user-friendly management, and potential utility in both tumor resections and neuronavigated biopsies favor its wider use in the surgical treatment of pediatric low-grade tumors.

Letter to the Editor: "The relationship between imaging features, therapeutic response, and overall survival in pediatric diffuse intrinsic pontine glioma".

This letter to the editor discusses the findings of Yu et al. (2024), which highlight the prognostic significance of volumetric assessments over cross-product measurements in pediatric diffuse intrinsic pontine glioma (DIPG). The study's methodology enhances precision in monitoring therapeutic responses, offering insights into treatment adjustments based on detailed imaging features. Emphasizing the value of volumetric MRI, this letter suggests its potential to improve surgical planning and therapeutic strategies, thereby optimizing patient management. This approach could revolutionize treatment paradigms, emphasizing personalized care through advanced imaging techniques.

Focus session on sodium fluorescein in pediatric oncological neurosurgery.

Many tools and techniques have been developed to obtain maximal safe tumoral resection in neurosurgery. Fluorescent dyes, including sodium fluorescein, have become also part of this armamentarium to localize the lesion and its boundaries peroperatively. Considering its alleged safety profile and its ability to diffuse in areas of altered blood-brain barrier, a typical characteristic of a number of both benign and malignant pediatric tumors, sodium fluorescein may appear an ideal candidate as intraoperative adjunct in pediatric neurosurgery. Nevertheless, a definitive role of this dye in children has not been established yet, and the reports on the pediatric population remain scarce. For this reason, we propose focusing on the use of sodium fluorescein in pediatric oncological neurosurgery by collecting articles reporting the result of the application of the technique in the management of intracranial pediatric tumors.

Risk for hydrocephalus, hygroma, and tumor dissemination after ventricular opening during resection of supratentorial neoplasms in children.

PURPOSE: The possibility that ventricular opening generates postoperative complications after surgical tumor treatment often restricts the degree of tumor resection. This study aims to determine whether the ventricular opening is associated with more complications in surgeries for resectioning supratentorial intra-axial brain tumors in the pediatric population. METHODS: A retrospective review analysis was performed of patients treated at IOP/GRAACC between 2002 and 2020 under 19 years of age and underwent surgery for supratentorial intra-axial primary brain tumor resection. Data were collected from 43 patients. RESULTS: Glial tumor was more common than non-glial (65% vs. 35%, p = 0.09). The ventricular opening was not related to neoplastic spreads to the neuroaxis (6% vs. 0, p > 0.9) or leptomeningeal (3% vs. 0, p > 0.9). Of the patients whose ventricle was opened, 10% developed hydrocephalus requiring treatment, while none of the patients in the group without ventricular opening developed hydrocephalus (p = 0.5). There was also no statistical difference regarding ventriculitis. Postoperative subdural hygroma formation correlated with the ventricular opening (43% vs. 0, p = 0.003). The survival at 1, 5, and 10 years of cases with the ventricular opening was 93.2%, 89.7%, and 75.7%, respectively, while in cases without ventricular opening, it was 100%, 83%, and 83%, respectively, respectively, with no statistical difference between the mortality curves. CONCLUSION: Our study demonstrated that ventricular violation was not associated with the occurrence of significant complications. It was related to the formation of subdural hygroma, which did not require additional treatment.

Fluorescein-guided resection for pediatric low-grade gliomas: institutional experience on two cases and a narrative literature review.

PURPOSE: Low-grade gliomas compose 30% of pediatric central nervous system tumors and outcomes of disease-free progression, and survival is directly correlated to the extent of resection. The use of sodium fluorescein (Na-Fl) is an intraoperative method in the localization of tumor cells in adult patients to optimize resection. Our purpose is to describe the use of Na-Fl in pediatric low-grade gliomas and its outcomes. METHODS: Patients under 18 years of age with low-grade gliomas at the author's institution underwent resection with the use of Na-Fl, with review of preoperative imaging findings, intraoperative results, and follow-up. Then, a comprehensive, narrative literature review of the use of Na-Fl in pediatric low-grade glioma was performed. RESULTS: Our single-institution use of Na-Fl in pediatric patients with suspected low-grade glioma demonstrated excellent results of intraoperative enhancement of tumor cells as well as gross total resection. The literature demonstrated 84% Na-Fl staining and 59.2% of gross total resection in pediatric low-grade gliomas with few small case studies, a range of reported findings, and few side effects. CONCLUSION: Na-Fl has a promising use in low-grade glioma resection in the pediatric patient population. Further research is warranted, such as randomized controlled studies, to assess Na-Fl as a potential tool in improving resection and long-term favorable outcomes.

The role of sodium fluorescein in pediatric supratentorial intra-axial tumor resection: new insights from a monocentric series of 33 consecutive patients.

INTRODUCTION: Surgical resection represents the mainstay of treatment, in pediatric central nervous system (CNS) tumors, and aggressive resection correlates with prognosis for several histotypes. Sodium fluorescein (SF), a green, water-soluble dye, is used as neurosurgical fluorescent tracer thanks to its property to accumulate in cerebral regions of blood-brain barrier disruption, acting as a valid tool to improve the extent of resection in tumors enhancing at preoperative MRI. Brain neoplasms represent a heterogeneous group of tumors in the pediatric age, constituting the most common solid cancers; they typically show a varying degree of contrast enhancement on MRI. MATERIALS AND METHODS: In March 2016, the authors started a prospective, observational trial to evaluate intraoperative fluorescence's characteristics of CNS tumors, the percentage of extent of resection, thanks to fluorescein aid, and side effects related to fluorescein administration. This report is based on a retrospective analysis of a group of 33 consecutive pediatric patients harboring a supratentorial lesion. RESULTS: In 17 of 33 (51.5%) procedures, fluorescence was reported as intense; in 14 of 33 (42.4%), moderate; and in 2 of 33 (6.1%), slight. Intraoperative fluorescence corresponds to preoperative-MRI-documented contrast enhancement. In 28 of 33 (84.8%) surgical procedures, SF was considered useful; in 2 of 33 (6.1%), partial useful; and in 3 of 33 (9.1%), not essential because the tumor was already recognizable. No adverse effect to SF administration was registered. CONCLUSION: Fluorescein-guided surgery with a dedicated filter on the microscope is a safe and effective technique to improve visualization and resection of different pediatric brain tumors.

Placement of EVD in pediatric posterior fossa tumors: safe and efficient or old-fashioned? The Vienna experience.

PURPOSE: The perioperative treatment of hydrocephalus in pediatric posterior fossa tumors with an external ventricular drain (EVD) is the treatment of choice in our center. We analyzed our experience in using EVD concerning safety and effectivity. METHODS: This is a single-center retrospective cohort study of 100 consecutive pediatric patients who underwent resection for a newly diagnosed tumor in the posterior fossa between 2011 and 2022. RESULTS: Of the 100 patients with posterior fossa tumors, 80 patients (80%) had radiological signs of hydrocephalus at presentation, 49 patients (49%) of whom underwent placement of an EVD. In 40 patients, the EVD was inserted at a mean of 2.25 days prior to the tumor resection; 9 had the EVD inserted during tumor resection (frontal trajectory in 7 patients, occipital trajectory in 2 patients). Histology revealed pilocytic astrocytoma in 48 patients, medulloblastoma in 32, ependymoma in 11, and other histologic entities in 9 patients. Gross total/near-total resection was achieved in 46 (95.83%) of the 48 pilocytic astrocytomas, 30 (93.75%) of the 32 medulloblastomas, and 11 (100%) of the 11 ependymomas. The mean number of total days with the EVD in place was 8.61 ± 3.82 (range 2-16 days). The mean number of days with an EVD after tumor resection was 6.35 ± 3.8 (range 0-16 days). EVD-associated complications were seen in 6 patients (12.24%) including one infection. None of these resulted in a worse clinical course or any long-term sequelae. Permanent CSF diversion at 6 months after surgery was necessary in 13 patients (13%), including two VP shunt, two SD-shunt, six endoscopic third ventriculostomy (ETV), and three combined VP shunt and ETV procedures. Patients with a medulloblastoma or ependymoma had a higher rate of permanent CSF diversion needed than the group of pilocytic astrocytoma patients (27.9% versus 2.13%, p < 0.001). In patients with metastatic disease, 7 of 17 patients (41.18%) needed a permanent CSF diversion, compared to 6 of 83 patients (7.23%) in the group without metastasis (p = 0.001). CONCLUSION: The treatment of hydrocephalus in pediatric posterior fossa tumors with an EVD as a temporary measure is safe and effective, provided that a multi-professional understanding for its handling is given and there is no need for a long transport of the children.

Review of imaging recommendations from Response Assessment in Pediatric Neuro-Oncology (RAPNO).

The Response Assessment in Pediatric Neuro-Oncology (RAPNO) working group includes neuroradiologists, neuro-oncologists, neurosurgeons, radiation oncologists, and clinicians in various additional specialties. This review paper will summarize the imaging recommendations from RAPNO for the six RAPNO publications to date covering pediatric low-grade glioma, pediatric high-grade glioma, medulloblastoma and other leptomeningeal seeding tumors, diffuse intrinsic pontine glioma, ependymoma, and craniopharyngioma.

Current Role and Future Potential of CSF ctDNA for the Diagnosis and Clinical Management of Pediatric Central Nervous System Tumors.

Most pediatric central nervous system (CNS) tumors are located in eloquent anatomic areas, making surgical resection and, in some cases, even biopsy risky or impossible. This diagnostic predicament coupled with the move toward molecular classification for diagnosis has exposed an urgent need to develop a minimally invasive means to obtain diagnostic information. In non-CNS solid tumors, the detection of circulating tumor DNA (ctDNA) in plasma and other bodily fluids has been incorporated into routine practice and clinical trial design for selection of molecular targeted therapy and longitudinal monitoring. For primary CNS tumors, however, detection of ctDNA in plasma has been challenging. This is likely related at least in part to anatomic factors such as the blood-brain barrier. Due to the proximity of primary CNS tumors to the cerebrospinal fluid (CSF) space, our group and others have turned to CSF as a rich alternative source of ctDNA. Although multiple studies at this time have demonstrated the feasibility of CSF ctDNA detection across multiple types of pediatric CNS tumors, the optimal role and utility of CSF ctDNA in the clinical setting has not been established. This review discusses the work-to-date on CSF ctDNA liquid biopsy in pediatric CNS tumors and the associated technical challenges, and reviews the promising opportunities that lie ahead for integration of CSF ctDNA liquid biopsy into clinical care and clinical trial design.

Building the ecosystem for pediatric neuro-oncology care in Pakistan: Results of a 7-year long twinning program between Canada and Pakistan.

BACKGROUND: Low- and middle-income countries sustain the majority of pediatric cancer burden, with significantly poorer survival rates compared to high-income countries. Collaboration between institutions in low- and middle-income countries and high-income countries is one of the ways to improve cancer outcomes. METHODS: Patient characteristics and effects of a pediatric neuro-oncology twinning program between the Hospital for Sick Children in Toronto, Canada and several hospitals in Karachi, Pakistan over 7 years are described in this article. RESULTS: A total of 460 patients were included in the study. The most common primary central nervous system tumors were low-grade gliomas (26.7%), followed by medulloblastomas (18%), high-grade gliomas (15%), ependymomas (11%), and craniopharyngiomas (11.7%). Changes to the proposed management plans were made in consultation with expert physicians from the Hospital for Sick Children in Toronto, Canada. On average, 24% of the discussed cases required a change in the original management plan over the course of the twinning program. However, a decreasing trend in change in management plans was observed, from 36% during the first 3.5 years to 16% in the last 3 years. This program also led to the launch of a national pediatric neuro-oncology telemedicine program in Pakistan. CONCLUSIONS: Multidisciplinary and collaborative efforts by experts from across the world have aided in the correct diagnosis and treatment of children with brain tumors and helped establish local treatment protocols. This experience may be a model for other low- and middle-income countries that are planning on creating similar programs.

Impact of dedicated pediatric neuro-oncological services in a developing country: A single-institution, Pakistani experience.

INTRODUCTION: Brain tumors are the most common solid neoplasms and the second most common malignancy in the pediatric age group. Due to the complexity of their management, pediatric central nervous system (CNS) tumors are not a priority in low- and middle-income countries (LMICs). METHODS: In an attempt to improve the survival rate and overall care, we introduced a dedicated pediatric neuro-oncology service in our institute and evaluated its impact by dividing the pre- and post-era into two cohorts and comparing them: 1998-2013 (16 years: cohort A) and 2014-2019 (6 years: cohort B, after the start of dedicated neuro-oncology services). RESULTS: We observed that after the implementation of a proper neuro-oncology service, the proportion of patients treated with curative intent increased, and survival improved in cohort B. The patient volume also increased from 15.5 per year in cohort A to 44.8 per year in cohort B. The percentage of children given radiation therapy also increased significantly, while the proportion of children treated with chemotherapy remained stable. CONCLUSION: A dedicated multidisciplinary team trained and knowledgeable in the specialty of pediatric neuro-oncology can enhance and improve outcomes, and supportive care and help can provide good quality of life to children and their families with brain neoplasms.

Late effects care for childhood brain Tumor Survivors: A Quality-Improvement Initiative.

Childhood and adolescent brain tumor survivors are at risk for long-term consequences of therapy. We reviewed adherence to long-term follow-up (LTFU) guidelines, assessed provider perspectives, and studied the needs, experience and quality of life (QOL) of pediatric malignant brain tumor survivors in the McMaster Children's Hospital Neuro-Oncology clinic. LTFU areas for improvement were evaluated using an anonymous health provider needs assessment questionnaire. The Cancer Care Experience Questionnaire (CCEQ), Cancer Worry Scale (CWS), Self-Management Skills Scale (SMSS), and PedsQL measured parents/patients' needs and QOL. Individual care plans were based on the Children's Oncology Group (COG) LTFU guidelines. Based on 17 responses, staff perceived areas for improvement included: increased multi-disciplinary participation, improved patient education and increased surveillance for therapy-related late effects. Thirty-two families participated, most felt they received high-quality care. Mean cancer worry scores were low (71.8 (± 28.4)). Survivors reported limited self-management skills (58.5 (±18.2)), requiring support with medical needs and activities of daily living. Overall median QOL scores were 'good' (parental report 72.3 (±17.7), survivor 68.2 (±16.6)). Utilizing survivorship guidelines and assessments from patients, caregivers and health providers, we implemented improvements in our provision of neuro-oncology survivorship care. Lessons learned may assist other LTFU programs.

A national overview of paediatric and adolescent and young adult surgical neuro-oncology in Pakistan.

OBJECTIVE: To build a comprehensive brain tumour database that will allow us to analyse in detail the prevalence, demographics, and outcomes of the disease in paediatric, adolescent, and young adult age groups. Method: A national cross-sectional study was conducted at 32 centres, and data regarding patient demographics and brain tumours were collected. This data was then stratified based on age groups, healthcare sectors, socioeconomic status, tumour types, and surgical outcomes. RESULTS: Most of the patients who were diagnosed with brain tumours belonged to a lower socioeconomic background and went to public sector hospitals. More males were diagnosed with and treated for brain tumours in the paediatric, adolescent, and young adult populations. The most common tumour in the paediatric population was medulloblastoma (23.7%) and the most common tumour in the adolescent (27.8%) and young adult population (34.7%) was glioma. Significant improvement in KPS scores were seen for: craniopharyngioma (p = 0.001), meningioma (p < 0.0005) and pituitary adenoma (p < 0.0005). CONCLUSIONS: This study shows that in all three age groups, there was a greater prevalence in males. Most of the patients belonged to a lower-middle-income class background and most patients presented to public sector hospitals. Greater knowledge of these parameters unique to each age group is the key to understanding and alleviating the burden of disease. Cancer registries, specifically brain tumour registries that keep up-to-date records of these patients, are essential to identify and keep track of these unique parameters to advance medical research and treatment strategies, ultimately lowering the disease burden.

Validated quantitative needs assessment differences in the management of children with central nervous system cancer between Brazil, an upper middle-income country, and the United States of America, a high income country.

BACKGROUND: Pediatric cancer cure rates differ among high-income countries (HIC) and upper middle-income countries (UMIC). We have compared individual capacities of two major referral pediatric centers from a HIC and an UMIC caring for children with central nervous system (CNS) cancer. METHODS: A quantitative needs assessment questionnaire and key informant interviews, distributed in March of 2017, were used to evaluate the treatment of children with CNS cancer at Grupo de Apoio ao Adolescente e à Criança com Câncer (GRAACC) children's cancer center in São Paulo, Brazil and Nationwide Children's Hospital (NCH) in Columbus, Ohio, United States of America (USA). RESULTS: Both hospitals had 24-hour pediatric oncology, nursing and intensivist coverage. Supportive care available at both institutions included social workers, psychologists, child life specialists, and physical/occupational/speech therapists. Differences included two part-time neuroradiologists and one pathologist specializing in neuropathology at IOP/GRAACC/UNIFESP, whereas eight full-time neuroradiologists and two neuropathologists at NCH/OSU. There were four pediatric neurosurgeons on staff at each hospital; however, there were only 2 operative days per week at IOP/GRAACC/UNIFESP, compared with 7 days at NCH/OSU. Additionally, time to initiation of radiation therapy at IOP/GRAACC/UNIFESP extended 2-4 weeks compared with less than 1 week at NCH/OSU. CONCLUSIONS: Center-specific differences in resources exist in highly specialized hospitals caring for children with CNS cancer in HIC and UMIC. This quantitative needs assessment may facilitate the development of targeted strategies for effective interventions to improve on the management of children with CNS cancers.

A phase I trial of lenalidomide and radiotherapy in children with diffuse intrinsic pontine gliomas or high-grade gliomas.

PURPOSE: This study was performed to determine the maximum tolerated dose (MTD) or recommended phase 2 dose (RP2D) of the immunomodulatory agent, lenalidomide, when administered daily during 6 weeks of radiation therapy to children with newly diagnosed diffuse intrinsic pontine glioma (DIPG) or high-grade glioma (HGG) PATIENTS & METHODS: Children and young adults < 22 years of age with newly diagnosed disease and no prior chemotherapy or radiation therapy were eligible. Children with HGG were required to have an inoperable or incompletely resected tumor. Eligible patients received standard radiation therapy to a prescription dose of 54-59.4 Gy, with concurrent administration of lenalidomide daily during radiation therapy in a standard 3 + 3 Phase I dose escalation design. Following completion of radiation therapy, patients had a 2-week break followed by maintenance lenalidomide at 116 mg/m2/day × 21 days of a 28-day cycle. RESULTS: Twenty-nine patients (age range 4-19 years) were enrolled; 24 were evaluable for dose finding (DIPG, n = 13; HGG, n = 11). The MTD was not reached at doses of lenalidomide up to 116 mg/m2/day. Exceptional responses were noted in DIPG and malignant glioma (gliomatosis cerebri) notably at higher dose levels and at higher steady state plasma concentrations. The primary toxicity was myelosuppression. CONCLUSION: The RP2D of lenalidomide administered daily during radiation therapy is 116 mg/m2/day. Children with malignant gliomas tolerate much higher doses of lenalidomide during radiation therapy compared to adults. This finding is critical as activity was observed primarily at higher dose levels suggesting a dose response.

Development of the Pediatric Neuro-Oncology Rating of Treatment Intensity (PNORTI).

Measures of treatment intensity for childhood cancer are needed in research in order to control for variability in treatments. Existing measures of treatment intensity for childhood cancers do not reflect the complexities of treatment protocols for central nervous system (CNS) tumors. This paper describes the development of the Pediatric Neuro-Oncology Rating of Treatment Intensity (PNORTI). PNORTI development occurred in three phases. Phase 1: five experts in pediatric neuro-oncology created a 5-point scale of treatment intensity and 42 pediatric neuro-oncology providers completed a three-part online questionnaire to evaluate the classification system and apply the rating system to 16 sample patients. Validity was determined by respondents classifying therapy modalities into intensity levels. Inter-rater reliability was calculated from ratings of the 16 sample patients. Phase 2: three experts revised the PNORTI based on survey results and 18 pediatric neuro-oncology providers evaluated the classification system. Phase 3: ten experts in pediatric neuro-oncology refined and finalized the PNORTI and rated 10 sample patients using the PNORTI. Agreement between median ratings of the survey respondents and criterion raters for chemotherapy intensity (r's = .82 and 1.0) and overall treatment intensity level (r's = .91 and .94) were high in Phases 1 and 2. Inter-rater reliability also was very high when using the PNORTI to classify the 16 sample patients in Phase 1 (median agreement of r = .93 and rICC = .99) and the 10 sample patients in Phase 3 (median agreement of r = .92 and rICC = .98). The PNORTI is a valid and reliable method for classifying the intensity of different treatment modalities used in pediatric neuro-oncology.

Current concepts and challenges in the radiologic assessment of brain tumors in children: part 2.

Assessing tumor response is a large part of everyday clinical work in neuroradiology. However in the setting of tumor treatment, distinguishing tumor progression from treatment-related changes is difficult on conventional MRI sequences. This is made even more challenging in children where mainstay advanced imaging techniques that are often used to decipher progression versus treatment-related changes have technical limitations. In this review, we highlight the challenges in pediatric neuro-oncologic tumor assessment with discussion of pseudophenomenon including pseudoresponse and pseudoprogression. Additionally, we discuss the advanced imaging techniques often employed in neuroradiology to distinguish between pseudophenomenon and true progressive disease.