CPT-SIOP registry: evaluation of risk factors for disease progression in pediatric choroid plexus papilloma.

PURPOSE: Choroid plexus papilloma (CPP) and atypical choroid plexus papilloma (aCPP) have excellent outcomes. However, some CPP/aCPP relapse and may qualify for postoperative adjuvant treatment. METHODS: German patients from the International CPT-SIOP Registry diagnosed with CPP/aCPP between 2011 and 2023 were included and analysed according to initial staging (postoperative residual tumor [R+], metastases [M+]), biology, postoperative treatment strategy and outcome. Additionally, patients from the published CPT-SIOP-2000 trial (PMID34997889) were combined with the registry cohort for validation purpose. 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 = 61, R+/M0 in n = 24, R0/M + in n = 5 and R+/M + in n = 3. aCPP was diagnosed in n = 38 patients. Molecular subgroup was available for n = 36: ”adult” n = 3, “pediatric A” n = 21 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. One patient with relapse died. Most patients did not receive postoperative treatment (n = 88). Five patients (R0/M + n = 2; R+/M + n = 1; R0/M0 n = 2) received postoperative chemotherapy. None was irradiated during first-line treatment. In the enlarged cohort (n = 197), histological diagnosis had a significant impact on PFS (5y-PFS: CPP 90 ± 3.1, aCPP 78.6 ± 4.6, PFS = 0.01). Both, R+ (5y-PFS: R0 90.6 ± 2.6, R + 69.1 ± 7.0, PFS = 0.01) as well as molecular subgroup “pediatric B” (5y-PFS: pediatric A 95.2%±3.3%, pediatric B: 69.5 ± 8.6%, PFS = 0.02), were associated with inferior PFS, especially in aCPP. CONCLUSION: Incomplete resection and biology impact on PFS especially in aCPP. These results extend the evidence for current stratification and treatment strategies.