ID #759 Outcomes following focal proton therapy for non-metastatic intracranial atypical teratoid/rhabdoid tumor (ATRT)
Daniel Indelicato, Raymond Mailhot-Vega, Elizabeth Thompson, Bryan Johnson, Chris Morris, Darren Klawinski, Nathan Ranalli, Julie BradleyAbstract
Background
In children with non-metastatic atypical teratoid/rhabdoid tumor (ATRT), proton therapy is increasingly utilized worldwide due to the radiosensitivity of afflicted young patients. General questions persist, however, surrounding dose and volume of radiotherapy.
Methods
Between 2009-2024, 39 children from a single institution with non-metastatic intracranial ATRT received focal proton therapy at a median age of 2.4 years (range 0.7-19). Twenty-two patients had supratentorial tumors and 27 had gross/near total resection prior to radiation. Most common chemotherapy regimens were ACNS0333 and SJYC07 (n = 10 each) and Dana-Farber (n = 6). Four patients received consolidative high-dose chemotherapy after radiation. The median radiation dose was 50.4 Gy (range, 50.4-54). The cumulative incidence method assessed freedom from selected endpoints.The Fine-Gray method assessed the level of statistical significance between levels of selected prognostic factors.
Results
With a median followup of 5.2 years (range 0.5-16.2), the 5-yr overall survival, progression-free survival, and local control was 63%, 64%, and 97%, respectively. Thirteen patients developed isolated leptomeningeal failure as first site of recurrence. Only subtotal resection was significantly associated with local recurrence (100% vs 92%, p < 0.05). Patient age, tumor site, extent of resection, radiation dose, and chemotherapy regimen were otherwise not significantly associated with disease control or survival. Four patients experienced symptomatic radiation necrosis, including 1 death: Three of 4 cases received 54 Gy and consolidative intrathecal methotrexate (n = 2) or high dose ACNS0333 intravenous chemotherapy (n = 1, fatal) after radiation. The other patient received 50.4 Gy and necrosis was immediately preceded by ventriculoperitoneal shunt failure. Six patients developed hearing loss requiring aids. One patient developed radiation-induced meningioma a decade following treatment.
Conclusion
This represents the largest experience reporting 5-year outcomes following focal radiation in children with non-metastatic intracranial ATRT. When applied with a variety of modern chemotherapy regimens in real-world settings, focal proton therapy at a dose of 50.4 Gy may offer the best therapeutic ratio but does not eliminate serious toxicity. If avoidance of craniospinal radiation remains an ongoing priority, further improvement in survival will depend upon systemic therapy.