TABLE 1.

Clinical ctDNA studies in pediatric cancer.

Cancer	Number of patients	Method of ctDNA detection	Target	Prognostic value	Reference(s)
Neuroblastoma	267	RQ-PCR	MYCN	Disease monitoring in patients with late-stage but not localized disease	Combaret et al., (2009)
Neuroblastoma	24	Microsatellite analysis (PCR)	11q loss	Treatment stratification	Yagyu et al., (2011)
Wilms tumor	120	Bi-sulfite sequencing	Differentially methylated regions (DMR)	Treatment stratification	Charlton et al., (2014)
Neuroblastoma	70	NGS	Copy number	Reflects tumor heterogeneity with potential for relapse prediction	Chicard et al., (2016)
Ewing sarcoma	20	ddPCR	EWSR1 fusions	Treatment response	Krumbholz et al., (2016)
Osteosarcoma	10	NGS	7 somatic aberrations	Potential for prognostic indication as ctDNA was detected before radiologic detection	Barris et al., (2018)
Osteosarcoma, neuroblastoma, Ewing sarcoma, Wilm’s tumor and alveolar rhabdomyosarcoma	46	NGS and ddPCR	Copy number variants and translocations	Treatment response and monitoring disease burden	Klega et al., (2018)
Ewing sarcoma and osteosarcoma	166	NGS	STAG2 and TP53 mutations, 8q gain	Potential for risk stratification	Shulman et al., (2018)
Diffuse intrinsic pontine glioma	15	NGS and ddPCR	H3K27M, TP53, PDGFRA, and ATRX mutations	Potential for guiding treatment decisions	Mueller et al., (2019)
Diffuse gliomas	85	NGS	IDH1, 1p/19q codeletion, TP53, TERT, ATRX mutations	Potential for disease monitoring	Miller et al., (2019)
CNS tumors	29	PCR	BRAF V600E	Potential for guiding treatment decisions	García-Romero et al., (2020)
Medulloblastoma	13	NGS and ddPCR	TP53 and PTCH1 mutations; MYCN and GLI2 amplifications; SUFU deletions and 17p loss	Diagnosis and MRD detection	Escudero et al., (2020)
Neuroblastoma	11	NGS	KMT2C, NOTCH1/2, CREBBP, ARID1A/B, ALK, FGFR1, FAT4 and CARD11	Potential for treatment stratification	Cimmino et al., (2020)
Neuroblastoma	32	NGS	5-Hydroxymethylcytosine (5-hmC)	Treatment response	Applebaum et al., (2020)
Hepatoblastoma	3	ddPCR	CTNNB1	Treatment response	Kahana-Edwin et al., (2020)
Neuroblastoma	56	RQ-PCR	RASSF1A	Disease monitoring	van Zogchel et al., (2020)
Ewing sarcoma	20	ddPCR	EWSR1 fusions	Treatment response	Schmidkonz et al., (2020)
Diffuse midline glioma	10	ddPCR	H3.3K27M mutation	Potential for monitoring disease and treatment response	Li et al., (2021)
Ewing sarcoma and other pediatric sarcoma	126	NGS	ctDNA fragmentation	Disease monitoring and treatment response	Peneder et al., (2021)
Neuroblastoma	13	ddPCR	MYCN, ALK and segmental chromosomal aberrations	Risk stratification and diagnosis	Kahana-Edwin et al., (2021b)
Diffuse midline glioma	32	ddPCR	Hotspot driver mutations and single fusion events	Disease monitoring and treatment response	Izquierdo et al., (2021)
Ewing sarcoma, osteosarcoma, rhabdomyosarcoma and synovial sarcoma	17	NGS	Translocations and complex chromosomal rearrangements	Treatment response and early detection of relapse	Shah et al., (2021)

Myelocytomatosis viral oncogene neuroblastoma derived homolog (MYCN), Stromal antigen (STAG2), Tumor protein p53 (TP53), Lys-27-Met mutations in histone 3 (H3K27M), Platelet-derived growth factor receptor A (PDGFRA), ATP-dependent helicase (ATRX), Isocitrate dehydrogenase 1 (IDH1), Telomerase reverse transcriptase (TERT), Proto-oncogene B-Raf and v-Raf murine sarcoma viral oncogene homolog B (BRAF), Patched 1 (PTCH1), GLI family zinc finger 2 (GLI2), Lysine Methyltransferase 2C (KMT2C), Notch receptor 1/2 (NOTCH1/2), Cyclic adenosine monophosphate Response Element Binding protein Binding Protein (CREBBP), AT-rich interactive domain-containing protein 1A (ARID1A), Anaplastic lymphoma kinase (ALK), Fibroblast growth factor receptor 1 (FGFR1), FAT atypical cadherin 4 (FAT4), Caspase recruitment domain family member 11 (CARD11), Catenin beta 1 (CTNNB1), Ras association domain family member 1 (RASSF1).