Craniospinal Irradiation Dose for Ependymoma with CSF Involvement
For ependymoma with CSF or spinal dissemination, craniospinal irradiation (CSI) of 36 Gy is recommended, followed by a boost to focal lesions up to 45-54 Gy. 1
Adult Patients
- Deliver 36 Gy CSI to the entire craniospinal axis when CSF cytology is positive or spinal MRI demonstrates dissemination 1
- Follow with a boost of 45-54 Gy to all focal lesions identified on imaging 1
- The total dose to the primary tumor bed should reach 54-60 Gy depending on WHO grade (60 Gy for grade III, 54-59.4 Gy for grade II) 1
- Use standard fractionation of 1.8-2.0 Gy per fraction 1
Pediatric Patients
- CSI is recommended for children with CSF or spinal dissemination, with boost doses on focal lesions adapted to patient age 1
- The specific CSI dose for children is not explicitly stated in the guidelines, but the boost to focal lesions follows age-adapted protocols 1
- For children >18 months without dissemination, local conformal RT up to 59.4 Gy is standard 1
- For children 12-18 months or those with poor neurological status, 54 Gy is recommended 1
Critical Staging Requirements Before Treatment
- Wait 2-3 weeks after surgery before performing staging studies to avoid false-positive results from post-operative changes 1
- Mandatory staging includes both craniospinal MRI with contrast AND CSF cytology to detect dissemination 1
- CSF sampling should be performed via lumbar puncture after spine imaging is completed 1
Evidence Quality and Nuances
The 36 Gy CSI dose recommendation comes from the 2018 EANO guidelines published in Neuro-Oncology, which represents the most authoritative and recent guideline evidence available 1. This recommendation applies uniformly to both adults and children when dissemination is documented.
The boost dose range of 45-54 Gy to focal lesions allows flexibility based on lesion location and patient tolerance, but the lower end (45 Gy) should be reserved for spinal metastases while the higher end (54 Gy) is appropriate for intracranial sites 1.
Common Pitfalls to Avoid
- Do not perform CSF cytology or spinal MRI immediately after surgery - wait the full 2-3 weeks to prevent false-positive findings from surgical contamination 1
- Do not use CSI prophylactically in the absence of documented dissemination - historical data show no benefit and increased toxicity 2, 3, 4
- Do not omit the focal boost - all recurrences occur locally even after CSI, making adequate boost doses essential 1, 2, 4
- In children, do not compromise on the CSI dose to reduce toxicity - local control remains the primary determinant of survival 1, 5
Pattern of Failure Data
Retrospective analyses consistently demonstrate that local recurrence within the primary tumor bed remains the dominant failure pattern even when CSI is administered 2, 3, 4. Out-of-field spinal failures without local recurrence are exceedingly rare 4. This underscores why adequate boost doses to the primary site are non-negotiable even when treating the entire neuraxis 1, 2.