BackgroundMany studies have demonstrated in the last years that once medulloblastoma has recurred, the probability of regaining tumor control is poor despite salvage therapy. Although re-irradiation has an emerging role in other relapsed brain tumors, there is a lack of strong data on re-irradiation for medulloblastoma. MethodsThis is a retrospective cohort study of patients aged 18 years or under, treated at least by a second course of external beam for recurrence medulloblastoma at Garrahan Hospital between 2009 and 2020. Twenty-four patients met eligibility criteria for inclusion. All patients received upfront radiotherapy as part of the curative-intent rst radiotherapy, either craniospinal irradiation (CSI) followed by posterior fossa boost in 20 patients or focal posterior fossa radiation in 4 infants. The second course of radiation consisted of CSI in 15 and focal in 9. The 3-year post rst failure OS (50% vs. 0%; p = 0.0010) was signi cantly better for children who received re-CSI compared to children who received focal re-irradiation. Similarly, the 3-year post-re-RT PFS (31% vs. 0%; p = 0.0005) and OS (25% vs. 0%; p = 0.0003) was signi cantly improved for patients who received re-CSI compared to patients who received focal re-irradiation. No symptomatic intratumoral haemorrhagic events or symptomatic radionecrosis were observed. Survivors fell within mild to moderate intellectual disability range, with a median IQ at last assessment of 58 (range 43-69). ConclusionRe-irradiation with CSI is a safe and effective treatment for children with relapsed medulloblastoma; improves disease control and survival compared with focal re-irradiation. However this approach carries a high neurocognitive cost.All radiation treatments were given at Garrahan Hospital, Buenos Aires, Argentina. Photon external beam therapy was used for all patients. All but four patients received CSI as part of the rst radiation course (RT1), followed by a boost to the entire posterior fossa. Standard risk (SR) patients received CSI 23.4Gy followed by posterior fossa boost 30.6Gy and high-risk (HR) patients received CSI 36Gy followed by posterior fossa boost 19.8Gy. Except for one, all of them received maintenance platinum based chemotherapy; SR as per ACNS0331 (N=2) and COG 9961 (regimen A=3, regimen B= 6); HR as per ACNS0332 (Regimen A=4, Regimen B=4). Four patients received upfront posterior fossa radiotherapy (54 Gy) due to the young age at diagnosis as per standard of care treatment administered between 2002 and 2020 at Hospital Garrahan, based on a modi ed POG-9934 strategy (15). Upon recurrence, most patients with brain solitary lesions were offered surgery followed by metronomic chemotherapy and a second course of irradiation (RT2), while those with multifocal disease received chemotherapy followed by radiotherapy. CSI was administered using standard beam's eye-view treatment planning techniques. Boost treatment and focal radiotherapy was administered using 3D-conformal radiation therapy methods. Hypofractionated stereotactic radiother...

Background Radiation necrosis is a frequent complication occurring after the treatment of pediatric brain tumors; however, treatment options remain a challenge. Bevacizumab is an anti-VEGF monoclonal antibody that has been shown in small adult cohorts to confer a benefit, specifically a reduction in steroid usage, but its use in children has not been well described. Methods We describe our experience with bevacizumab use for symptomatic radiation necrosis at 5 institutions including patients treated after both initial irradiation and reirradiation. Results We identified 26 patients treated with bevacizumab for symptomatic radiation necrosis, with a wide range of underlying diagnoses. The average age at diagnosis of radiation necrosis was 10.7 years, with a median time between the last dose of radiation and the presentation of radiation necrosis of 3.8 months (range, 0.6-110 months). Overall, we observed that 13 of 26 patients (50%) had an objective clinical improvement, with only 1 patient suffering from significant hypertension. Radiological improvement, defined as reduced T2/fluid-attenuated inversion recovery signal and mass effect, was observed in 50% of patients; however, this did not completely overlap with clinical response. Both early and late radiation necrosis responded equally well to bevacizumab therapy. Overall, bevacizumab was very well tolerated, permitting a reduction of corticosteroid dose and/or duration in the majority of patients. Conclusions Bevacizumab appears to be effective and well-tolerated in children as treatment for symptomatic radiation necrosis and warrants more robust study in the context of controlled clinical trials.

Background: Intracranial germ cell tumor (iGCT) represents a rare and heterogeneous group, with variable incidence and diverse treatment strategies. Although multiagent chemotherapy with reduced radiotherapy strategy has been applied by several cooperative groups in North America and Western Europe, there is a paucity of data to understand if this combined regimen issuitable in low-middle income countries (LMIC). Methods: We evaluate the outcome in a cohort of iGCT treated by SIOP-CNS-GCT-96 strategy at Hospital J.P Garrahan in Argentinaover the last 20 years. Radiation field and dose included focal radiotherapy (FRT) before 2009 or focal radiotherapy plus whole ventricular radiotherapy (WVRT) after 2009 for localized germinoma and FRT or FRT plus WVRT or CSI for non germinomatous germ cell tumors (NGGCT) Results: Sixty iGCT were identified; 39 germinoma and 21 NGGCT. Median follow-up was 6.57 years (range 0.13-20.5). Five-year PFS and OS were 83.5% (95% CI [165.53-223.2]) and 88.7% (95% CI [169.84-223.2]) for the germinoma group, while for the NGGCT group were 75% (95% CI [133.27-219.96]) and 64.2% (95% CI [107.38-201.81]) respectively. The localized germinoma group showed poor results between 2000-2009 with 5-year PFS and OS of 69% and 75% respectively, and an excellent outcome between 2010-2019 with a 5-years PFS and OS of 92.8% and 100%. A univariable analysis identified this difference in survival as related to the field of radiotherapy, specifically whole ventricular radiotherapy. FRT increased the risk of recurrence in localized germinoma, involving not only 4 ventricular relapses; but spinal cord and disseminated disease as well. There were no relapses of localized NGGCT after FRT and FRT plus WVRT. Conclusion: Herein we demonstrate that intensive chemotherapy followed by FRT plus WVRT for germinoma is a feasible and effective strategy, warranting further study in the developing world.

Central nervous system high-grade neuroepithelial tumor with MN1 alteration (CNS HGNET-MN1) is a rare recently described entity. Fourteen CNS HGNET-MN1 patients were identified using genome-wide methylation arrays/RT-PCR across seven institutions. All patients had surgery (gross total resection: 10; subtotal resection: four) as initial management followed by observation alone in three patients, followed by radiotherapy in eight patients (focal: five; craniospinal: two; CyberKnife: one) and systemic chemotherapy in three patients. Seven patients relapsed; five local and two

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