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Proton-Based Re-Irradiation of Locally Recurrent Pediatric Brain Tumors in Close Proximity to the Brainstem
Insights
Proton therapy re-irradiation effectively controls pediatric brain tumors near the brainstem. This advanced proton therapy (PT) approach shows promising local control and survival rates with minimal toxicity.
Area of Science:
- Pediatric Oncology
- Radiation Oncology
- Neuro-oncology
Background:
- Local recurrence of aggressive pediatric brain tumors presents a significant clinical challenge.
- Re-irradiation strategies are crucial for managing tumor failures, especially near critical structures like the brainstem.
Purpose of the Study:
- To evaluate the efficacy and safety of full-course re-irradiation using proton therapy (PT) for pediatric patients with local tumor failures adjacent to the brainstem.
Main Methods:
- Eleven children with recurrent brain tumors (ependymoma, atypical teratoid rhabdoid tumor, etc.) received fractionated re-irradiation with pencil beam-based PT.
- Treatment planning involved cumulative dose summation and individualized organ-at-risk (OAR) dose constraints, particularly for the brainstem.
- Median prescribed re-irradiation dose was 54.0 Gy(RBE), delivered in fractions of 1.8-2.2 Gy(RBE).
Main Results:
- At a median follow-up of 42.5 months, 82% of patients achieved local control.
- Actuarial 2- and 3-year local control rates were 89% and 76%, respectively.
- No central nervous system (CNS) toxicities of Grade 2 or higher were observed, including no symptomatic brainstem or brain necrosis.
Conclusions:
- Selective re-irradiation with pencil beam proton therapy, employing modified treatment planning, is an effective and safe modality for pediatric brain tumors.
- This approach demonstrates significant local control and survival benefits, even in challenging cases involving tumors abutting the brainstem.
Purpose:
Local recurrence of aggressive, pediatric brain tumors remains a challenge. We offered full-course re-irradiation with proton therapy (PT) to children with local failures in proximity to the brainstem.
Patients And Methods:
Eleven children (7 male, 4 female) underwent fractionated re-irradiation using pencil beam-based PT for local recurrence following maximum prior multidisciplinary treatment for ependymoma (N = 6), atypical teratoid rhabdoid tumor (N = 3), papillary tumor of the pineal region (N = 1) and atypical meningioma (N = 1).Median age at first radiotherapy (RT) was 4.5 years (range: 1.5-14.8); at re-RT was 6.7 years (range: 3.0-18.9); median interval between courses was 21 months (range: 13-160). In 9/11 children Gross Tumor was identifiable.Primary RT was with photons (N = 6) or protons (N = 5). Re-RT planning was based on cumulative dose summation. Permissible re-RT OAR doses were individualized. Median prescription dose was 54.0 Gy(RBE) (range 44.0-54.0). All re-treatments were delivered at 1.8-2.2 Gy(RBE) per fraction. A constant RBE value of 1.1 was used.
Results:
At median follow-up of 42.5 months (range 7-63), 9 /11 children (82%) achieved local control. Actuarial 2- and 3-year local control and overall survival rates were 89% and 76%, and 82% and 73%, respectively.Strategies of balancing target dose with OAR considerations resulted in a median cumulative brainstem surface dose (D0.1cc) of 81.5 Gy(RBE) (range: 65.8-99.48). No CNS toxicities ≥ Grade 2 were observed, specifically no symptomatic brainstem or brain necrosis.
Conclusion:
Selective re-irradiation with pencil beam-based proton radiotherapy, using specifically modified treatment planning approaches, can be effective and safe, even in cases with tumor abutting the brainstem.
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