Abstract BACKGROUND After SIOP-CNS-GCT-II closed in 2018, the CCLG recommended, with caveats, following standard trial arms: 4 Cisplatin-Etoposide-Ifosfamide (PEI) cycles, then focal radiotherapy (FRT) (54Gy/30fractions) to primary site(s) for localised NGGCT and craniospinal-irradiation (CSI) (30Gy/20fr) + boosts (24Gy/15fr cranial, 20.8Gy/13fr spinal) for metastatic disease. Since 04/2021, the CCLG formally recommended adding WVRT (24Gy/15fr) for localised NGGCT, and considering 2x standard, 2x high-dose PEI for high-risk (HR) cases (diagnostic AFP>1000ng/ml). METHODS Retrospective review of all CNS-NGGCT patients referred 12/2018-06/2023. We collected patient, tumour and treatment factors, acute toxicities (CTCAE grade≥3), and event-free survival (EFS) from radiotherapy until 09/2023. RESULTS Twenty-four patients (21M:3F) included, 14 localised (4xHR), 10 (including 2 incompletely staged) treated as metastatic (3xHR). Median age 11 years, median follow-up 16 months (m). Primary sites: 13 pineal, 5 pituitary/suprasellar, 6 bifocal. Patients were treated according to CCLG guidance. One received FRT without WVRT. One incompletely staged bifocal standard-risk (SR) NGGCT after partial response to PEI had surgery, local+metastatic progression, then second-line chemotherapy before CSI. All seven HR patients received intensified chemotherapy. Nine had post-chemotherapy surgery for residual, two showing necrosis/inflammation, three mature teratoma, two mixed viable GCT. Three relapses (1/17 SR, 2/7 HR) made early EFS 0.875. Of 13 localised patients receiving WVRT, 2 progressed. One bifocal SR patient developed spinal metastases at 5.0m and died despite chemotherapy+spinal irradiation. One unifocal HR patient developed posterior parafalcine metastasis at 3.9m, received GemPOx (Gemcitabine-Paclitaxel-Oxaliplatin), surgery, high dose Carboplatin-Etoposide-Thiotepa with stem-cell rescue, and photon CSI and remains disease-free at 13.2m. One metastatic HR patient progressed at 0.9m and died at 3.0m despite chemotherapy. Acute toxicities were grade 3 lymphopenia in two CSI patients. CONCLUSIONS Despite short follow-up, initial EFS is excellent in SR disease. No localised WRVT-receiving NGGCT patient progressed within the ventricular volume, suggesting benefit of low-dose WVRT.
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