Background
Prospective institutional series. 60 children and young adults (median age 7 years) with intracranial ependymoma treated with proton RT at MGH 2000–2012. First large series to report outcomes and toxicity profile of proton therapy specifically for ependymoma, with dosimetric comparison to photon conformal RT.
Interventions and follow up
Arm A: Proton RT 55.8 Gy(RBE) (grade II/low-grade) or 59.4 Gy(RBE) (grade III/anaplastic) in 1.8 Gy fractions, pencil-beam scanning or passively scattered proto
Primary endpoint: Local control, EFS, OS, and neurocognitive outcome
mFollow up: 5.1 year
Primary endpoint: Local control, EFS, OS, and neurocognitive outcome
mFollow up: 5.1 year
Results
5-yr local control: 78% (grade II) vs 58% (grade III)
5-yr EFS: 76% (grade II) vs 46% (grade III)
5-yr OS: 95% (grade II) vs 67% (grade III)
Neurocognitive: IQ relatively stable compared to historical photon cohorts; mean FSIQ −0.6 points/year
5-yr EFS: 76% (grade II) vs 46% (grade III)
5-yr OS: 95% (grade II) vs 67% (grade III)
Neurocognitive: IQ relatively stable compared to historical photon cohorts; mean FSIQ −0.6 points/year
Adverse events
Main adverse events: Grade ≥3 late toxicity in 10%: hearing loss 7%, growth hormone deficiency 8%. Significant reduction in dose to cochlea, hypothalamus, and contralateral temporal lobe vs photon RT. No radiation necrosis requiring intervention.
Conclusions
Proton RT achieves local control and survival outcomes comparable to photon conformal RT in pediatric ependymoma while significantly reducing dose to critical normal structures. The reduced neurocognitive decline rate supports proton therapy as the preferred modality for this population.
Key Limitations
Key Limitations: Single-institution series without randomized comparison to photon RT. Selection bias possible (patients able to travel to proton center). Neurocognitive comparison to historical photon cohorts is limited by era effects and differences in testing protocols.
Clinical Context
MGH data, along with similar series from St. Jude and MD Anderson, drove adoption of proton therapy as preferred modality for pediatric ependymoma at major pediatric oncology centers. The NRG/COG ACNS1123 trial (proton vs photon) is ongoing. Current NCCN and COG guidelines support proton therapy when available.
References
References: MacDonald SM et al, IJROBP 2013 (MGH proton)