ID #552 Pediatric Metastatic Medulloblastoma: Upfront biopsy followed by oncological treatment without excision of the primary tumor

Objectives Advancements in medulloblastoma management have improved survival; however, high-risk metastatic cases remain challenging, with ∼60% 5-year event-free survival and significant long-term toxicity. Standard treatment includes resection of the posterior fossa tumor, followed by multimodal oncologic therapy. Yet, primary tumor resection may result in treatment delay, and sometimes surgical morbidity. We hypothesize that a biopsy-only approach may enable prompt oncologic treatment in patients with metastatic disease and minimize surgical morbidity, without compromising long-term survival. Methods We retrospectively reviewed medical records from a tertiary pediatric center (2010–2023) for patients under 18 years diagnosed with metastatic medulloblastoma who underwent biopsy (± CSF diversion) without primary tumor resection. Clinical, surgical, pathological, molecular, and imaging data were analyzed. Tumor response was evaluated via MRI. Results Between 2010 and 2023, 50 study eligible patients with medulloblastoma were treated at our medical center (70% males). Out of those 12 male metastatic patients met the inclusion criteria (mean age 6.5 years, range 1.1–16.1). Median follow-up was 3.2 years. At analysis, 9 patients (75%) were alive, with an estimated 5-year survival of 63%. Three deaths occurred; two in patients with ultra-high-risk MYC-amplified tumors, and one in a patient with a late supratentorial relapse. No cases of posterior fossa syndrome were observed. All survivors showed stable or resolving residual MRI abnormalities without progressive disease. Conclusion In metastatic pediatric medulloblastoma patients, primary tumor resection may be avoidable. A biopsy-based approach followed by timely multimodal therapy may preserve survival outcomes while minimizing surgical risks, as long-term prognosis is probably related to disease subtype and prompt oncologic treatment. This strategy warrants further investigation and may have broader implications for medulloblastoma treatment paradigms.