Pediatric metastatic medulloblastoma: upfront biopsy followed by oncological treatment without excision of the primary tumor

OBJECTIVE: Advancements in medulloblastoma management have improved survival; however, high-risk metastatic cases remain challenging, with approximately 60% 5-year event-free survival and significant long-term toxicity. Standard treatment includes resection of the posterior fossa tumor, followed by multimodal oncological therapy. Yet, primary tumor resection can result in treatment delay and sometimes surgical morbidity. The aim of this study was to evaluate outcomes and assess the potential of a treatment approach that includes biopsy only followed by chemotherapy and radiation therapy as a viable alternative in selected clinical scenarios. METHODS: This retrospective study included pediatric patients (age < 18 years) who were diagnosed with metastatic medulloblastoma and underwent biopsy (with or without CSF diversion) without primary tumor resection at a tertiary pediatric center between 2010 and 2023. Clinical, surgical, pathological, molecular, and imaging data were analyzed. Tumor response was evaluated on MRI. RESULTS: During the study period, 60 patients with medulloblastoma were treated at the medical center; 12 male patients (mean age 6.5 years, range 1.1-16.1 years) with metastatic disease who were treated with the upfront biopsy-only approach met the inclusion criteria. The median follow-up duration was 3.2 years. At the time of analysis, 9 patients (75%) were alive, with an estimated 5-year survival rate of 63%, and 3 patients had died (2 with very high-risk MYC-amplified tumors and 1 with a late supratentorial relapse). No cases of posterior fossa syndrome were observed. All surviving patients showed stable or resolving residual abnormalities on MRI without progressive disease. CONCLUSIONS: In pediatric patients with metastatic medulloblastoma, primary tumor resection might be avoidable. A biopsy-based approach followed by timely multimodal therapy can preserve survival outcomes while minimizing surgical risks, as long-term prognosis is likely related to the disease subtype and prompt oncological treatment. The proposed strategy warrants further investigation and might have broader implications for medulloblastoma treatment paradigms.