ETMR-17. CLINICAL DESCRIPTION OF PEDIATRIC CHOROID PLEXUS PAPILLOMAS FOR IDENTIFICATION AND VALIDATION OF HIGH-RISK CHARACTERISTICS

Abstract

Abstract BACKGROUND Choroid plexus papilloma (CPP) and atypical CPP (aCPP) have an excellent prognosis. However, some CPP/aCPP relapse and may qualify for postoperative treatment. METHODS Patients from the International CPT-SIOP Registry with CPP/aCPP recruited in Germany between 2011–2023 were included and analysed according to initial staging (postoperative residual tumor [R+], meningeosis [M+]), biology, postoperative treatment and outcome. RESULTS Ninety-three patients were identified (male: n=53, female: n=40). Median age at diagnosis was 1.9(0.1–17.6) years. Initial staging was R0/M0 in n=63, R+/M0 in n=21, R0/M+ in n=5 and R+/M+ in n=4. aCPP was diagnosed in n=38. Methylation subtype was available for n=34:”adult” n=3, “pediatric-A” n=19 and “pediatric-B” n=12 (6/12 aCPP). Median follow-up was 5.5(±0.99) years. Twelve tumors relapsed: R0/M0 n=4, R+/M0 n=7, R+/M+ n=1. Two relapsed patients died. Eleven patients initially received ≥1 surgery. Most patients did not receive postoperative treatment (watchful waiting, n=86). Seven patients (R0/M0 n=3, R+/M0 n= 1, R0/M+ n=2, R+/M+ n=1) received chemotherapy. None was irradiated during first-line treatment. Histology and biology had no impact on PFS (5y-PFS: CPP 88.6±4.9%, aCPP 82.7±6.5%, pPFS=0.3; “adult” 33.3±27.2%, “pediatric-A” 93.8±6.1%, “pediatric-B” 72.9±13.5%, pPFS=0.08). Patients with R0/M0-status had better 5y-PFS than those with R+ and/or M+ (90.4±4.1% vs. 77.7±8.1%, p=0.05). Neither incomplete resection alone, nor meningeosis alone did relate to inferior PFS in CPP/aCPP separately analysed (R+: p=0.07/p=0.07, M+: p=0.5/p=0.4). In the whole cohort, R+ was associated with inferior survival (5y-PFS R+ 72.2±9.8% vs. R0 91.3±3.7%, p=0.009). It remains unclear if R+-patients benefit from chemotherapy (5y-PFS watch-and-wait vs. chemotherapy 75.1±9.8% vs. 50.0±35.4% pPFS=0.7). CONCLUSION Incomplete resection appears to have impact on the risk for relapse in CPP/aCPP. It remains unclear whether those patients benefit from postoperative chemotherapy.