ACNS0121

Background

Phase II single-arm trial. 356 children (1–21 years) with intracranial ependymoma (grade II or III, supratentorial or infratentorial). Enrolled 2003–2010. Goal: evaluate conformal RT after surgery with standardized neuroimaging and surgical definitions; assess local control with modern conformal techniques.

Interventions and follow up

Arm A: Conformal RT 59.4 Gy in 33 fractions (1.8 Gy/fraction) to a 1.0 cm CTV margin around postoperative tumor bed
Primary endpoint: Local failure-free survival (LFFS)
mFollow up: 7.0 year

Results

5-yr LFFS: 69.1% (grade II) vs 56.8% (grade III)
5-yr EFS: 57.8% overall
5-yr OS: 81.0% overall
Gross total resection 5-yr LFFS: 76.0% vs subtotal resection 43.0%

Adverse events

Main adverse events: Acute: fatigue, nausea. Late: neurocognitive decline reported separately; grade ≥3 late toxicity uncommon in this report. Endocrine deficiency in 17% at 5 years.

Conclusions

Conformal RT to 59.4 Gy achieved durable local control in pediatric ependymoma, particularly after gross total resection. The 1.0 cm CTV margin with conformal technique allowed adequate dose delivery with acceptable toxicity.

Key Limitations

Key Limitations: Single-arm design without randomization limits interpretation. Surgical completeness varied and was a dominant predictor of outcome — surgical quality was not prospectively standardized. Grade II vs III distinction was based on WHO 2000 criteria; current WHO molecular classification (RELA fusion, YAP1 fusion) was not available, potentially mixing prognostically distinct entities.

Clinical Context

Established 59.4 Gy conformal RT as the standard adjuvant approach for pediatric ependymoma after maximal safe resection. GTR followed by RT is the current standard; role of chemotherapy remains unclear. Proton therapy has been adopted at many centers to reduce dose to normal brain.

References

References: Merchant TE et al, JCO 2015 (ACNS0121)