Abstract BACKGROUND Atypical choroid plexus papilloma (ACPP) and choroid plexus carcinoma (CPC) are rare malignant tumors of the central nervous system. Complete resection, the most important prognostic variable for long-term survival, is often limited by tumor vascularity and voluminous size in children. While systemic chemotherapy is known to reduce tumor volume and intra-operative blood loss, children often experience dose-limiting side effects. We hypothesize the use of intra-arterial (IA) chemotherapy for newly diagnosed, recurrent, or residual CPC/ACPP would increase likelihood of achieving complete resection in a safer manner. OBJECTIVE To assess the safety, feasibility, and effect of pre-operative IA chemotherapy for CPC/ACPP. METHOD The patient was treated according to phase I clinical trial protocol (NCT04994977) which consists of a single IA chemotherapy administration of melphalan, topotecan, and carboplatin followed by MRI-based response assessment to determine eligibility for second-look surgery. Primary endpoints are serious adverse events, and secondary endpoints include angiographic procedural success, tumor volume reduction on MRI, extent of resection and caclulated blood loss (CBL), and pathologic correlates of vascularity and tumor viability. RESULT 7-year-old male with Li-Fraumeni syndrome was enrolled for residual CPC (4.8 x 4.6 cm) after three prior resection attempts were limited by significant blood loss. Pre-operative IA chemotherapy was delivered to two targets without complication: the right posterolateral and anterior choroidal arteries. Five weeks later, MRI confirmed tumor volume reduction of 6.3%. On angiographic evaluation for administration of pre-surgical embolization, a significant reduction in angiographic hypervascularity was found, and liquid embolic embolization was not pursued. Craniotomy resulted in gross total resection without transfusion requirement and minimal CBL. Pathology demonstrated reduced proliferative index (Ki67 4% versus 10% in prior tissue). CONCLUSION Early phase results indicate pre-operative IA chemotherapy for residual CPC/ACPP may serve as safer bridge to second look surgery by decreasing tumor volume and vascularity.