Sustained Disease Control with Niraparib in a Pediatric Patient withRecurrent Atypical Teratoid/Rhabdoid Tumor: A Case Report

Introduction/Background: Atypical Teratoid/Rhabdoid Tumor (AT/RT) is an aggressive pediatric CNS malignancy. SMARCB1/INI1 loss induces genomic instability and homologous recombination deficiency, supporting the use of PARP inhibitors via synthetic lethality. However, clinical data in children are lacking. We report the first case of sustained response to niraparib in recurrent, radiotherapy-refractory AT/RT. Case Presentation: A 10-year-old boy with INI-1-negative AT/RT recurred post-resection and failed radiotherapy. He received off-label niraparib (100mg/day). Grade 3/4 hematologic toxicity occurred but was manageable. Serial MRIs showed lesion reduction and stabilization. Disease control has been maintained for > 20 months. Conclusion: Niraparib monotherapy can provide durable disease control in molecularly selected pediatric AT/RT, confirming the therapeutic potential of PARP inhibition in INI-1- deficient tumors and highlighting the need for prospective trials.