RARE-12. Pineoblastoma of children and young adults in a national population: An analysis of the HIT-MED study cohort

BACKGROUND: Pineoblastoma is a malignant tumor of the pineal gland and accounts for <1% of all pediatric brain tumors. PURPOSE/METHODS: Patients <21 years (y) with pineoblastoma confirmed by central neuropathology review between 2001–2021 and included into the HIT2000 trial, HIT2000interim- or I-HIT-MED-registries were eligible. RESULTS: 88 patients were identified. Age at diagnosis was 0.01–20.71y (median 9.34y), median follow-up was 6.54y (IQR 1.78–12.41y) in 48 patients alive at last follow-up. 20 patients were <4y and received chemotherapy with intent to avoid radiotherapy. Of these, 7 patients were alive at last follow-up, two patients were radiotherapy-naïve and 5 patients had undergone CSI + boost (4 after incomplete response and one after progression). 5-y-PFS/OS in 68 patients >4y differed according to metastatic status (M0 (n=40) 72.7±8.3%/75.0±8.3%; M+ (n=28) 28.7±10.3%/40.8±10.9%, p=0.001/0.001). Therapy escalation in M0 patients by giving SKK chemotherapy before radiotherapy did not improve PFS/OS compared to upfront radiotherapy (5-y-PFS/OS 70.7±14.3%/70.0±14.5% vs 74.2±10.1%/78.9±9.4%, p=0.61/0.73). Applied CSI dosages were 24–50Gy (mean 35.6Gy) with no prognostic value of specific dosages being observed. Similarly, in M0 patients hyperfractionated radiotherapy (2x1.0Gy/d, total dose (TD) 36Gy, n=23) was not superior to conventional radiotherapy (1.6Gy/d, TD 35.2Gy, n=7). In all patients, favorable prognostic factors were age >4y (5-y-PFS/OS 54.1±7.0%/60.0±7.0% vs 30.0 ±10.2%/35.0±10.7%, p=0.012/0.053) and radiotherapy in primary therapy (5-y-PFS/OS 55.8±6.5%/61.4±6.4% vs 14.4±9.4%/21.4±11.0%, p<0.001/=0.003), whereas unfavorable prognosis was associated with metastatic disease (5-y-PFS/OS 33.6±9.0%/45.9±9.3% vs 58.8±7.6%/59.3±7.7%, p=0.028/0.086). CONCLUSION: Survival is poor in pineoblastoma patients <4y treated without radiotherapy. Unfavorable prognosis was associated with metastatic disease, especially in older children. Chemotherapy combined with CSI is effective for non-metastatic patients at age >4y. Further research will consider biological subgroups to enhance risk stratification and identify approaches for therapy improvements.