Table 2.
CTC detection in glioblastoma multiforme (GBM) patient blood.
| CTC isolation/ID Method (Reference) | Patient No. | CTC Counts # | Efficiency * | Biomarker Tested | Clinical Utility | Limitations |
|---|---|---|---|---|---|---|
| Lentiviral telomerase reverse transcriptase (TERT)-promoter based detection [7] | 11 | 8.8 (pre-RT) | pre-RT: 72% (8/11) post RT: 8% (1/11) |
Epidermal growth factor receptor (EGFR) amplification | Prognostic marker (increased CTC count with recurrence) | Small cohort size, requires viral transduction limited to viable cells, may affect biomarker detection |
| Gradient PBMCs/CTC enrichment, immunocytostainig for glial fibrillary acidic protein (GFAP) [11] |
141 | 0.1–2.2 | 20.6% (29/141) | EGFR amplification | No correlation with OS | GFAP heterogeneous in GBM, use as sole ID marker may under-estimate CTC counts |
| CTC-ichip leucocytes depletion, CTC ID with probing for SOX2, Tubulin b-3, EGFR, A2B5 and c-MET [72] | 33 | 11.8 (progressive disease) 2.1 (stable disease) |
39% (13/33) | N/A | Prognostic marker (progressive disease with greater frequency of CTCs) | Small cohort size |
| FISH CTC detection (chromosome 8 polyploidy) and exclusion of CD45+ cells [69] |
31 | 0.13–1.33 | 71% (24/31) | N/A | CTC count decreases post adjuvant therapy, CTCs may help distinguish radio-necrosis from true tumor progression | Small cohort size |
| Parsortix platform for size based CTC capture, CTC ID testing by EGFR, Ki67, EB1 probing [73] | 13 | 0.3, 1 patient: CTC clusters | 53.8% (7/13) | NGS: APC, XPO1, TFRC, JAK2, BRCA2, ERBB4 and ALK | N/A | Small cohort size |
| VAR2CSA malaria protein based targeted immunomagnetic isolation [74] | 5 (GBM) | 3.5~ | 80% (4/5) | NGS: IDHI, RB1, ALK, LOH 1p/19q, MGMT | N/A | Small cohort size, use of VAR2CSA for both isolation and ID may reduce specificity of CTC detection |
| MCAM, MCSP targeted immunomagnetic isolation, GFAP and GLAST probing [75] | 13 (15 samples) | 1.5 | 60% (9/15) | N/A | No correlation of CTC counts with PFS/OS | Small cohort size |
ID CTC identification, # Average CTC counts detected normalised per 1 mL blood; * proportion of CTC positive patients; RT radiotherapy; N/A not applicable; ~estimated from graph in [74] for 5 GBM patients.