a, Ptch+/−/Math1-SB11/T2Onc mice with medulloblastoma underwent subtotal tumour removal (n = 38) and received multi-fractionated CSI post-operatively. Radiation was delivered under computed tomography (CT) guidance. b, Microneurosurgery and CSI strikingly improves tumour-free survival as compared to untreated controls (P = 0.0001, log-rank test, n = 64). Inset schematic indicates the fractionation schedule. c, Venn diagrams demonstrate the paucity of overlap in the gCISs between primary tumours and their recurrences. d, Drosophila brain tumours harbouring wild-type P53 displayed massive apoptosis in response to 40 Gy irradiation. e, Dominant negative P53 (p53R159N) essentially abrogated the radiation-dependent cell death. Scale bar, 50 µm.