MDB-09. WNT and Group 4 Medulloblastomas of Early Childhood Treated With High Dose Chemotherapy and Craniospinal Irradiation Sparing Approach

BACKGROUND WNT and group 4 medulloblastoma (MB) are rare in young children and their outcome when treated with radiation avoidance infant strategies is unknown. METHOD This retrospective international cohort included children less than 7 years of age, with molecularly characterized group 4 or WNT MB, treated with high-dose chemotherapy(HDC) and CSI sparing approach. RESULTS The current cohort includes 29 patients (19M/10F). For the 26 patients with group 4 MB (median age at diagnosis 45.9 months), 16 (61.5%) were M0 and 17 (65.3%) underwent initial gross total resection (GTR). The most common consolidation regimen used was three cycles of high dose carboplatin and thiotepa (65.5%) or a single cycle of high dose of carboplatin, etoposide and thiotepa (31%).Two received adjuvant focal radiotherapy. Sixteen patients (61.5%) relapsed at a median time of 21.4 months from diagnosis (median age of 5.2 years). Relapse was local for 50% of the patients. One patient underwent palliative management and 15 received radiation-based salvage therapy (2 focal, 13 CSI+/- boost).The median dose of CSI was 36Gy (18-36). Five of the 15 died of disease. Overall, at a median follow-up of 37.9 months from diagnosis, 17/26 (65.3%) patients were alive, six had died of disease and two of toxicity. All 3 WNT patients (median age at diagnosis 57.8 months) underwent GTR and two were M0. Two received sequential high dose carboplatin and thiotepa. One patient with initial partial response, progressed 2 months after treatment completion and received salvaged CSI (18Gy). All of them were alive at a median follow up of 88 months from diagnosis. CONCLUSIONS HDC and CSI sparing approaches led to a high rate of relapse for young patient with group 4 (61.5%). However, 2/3 were salvaged with radiation-based therapy given at a median age 5.2 yrs. Additional WNT patients are needed to better describe their management.