Real-time monitoring of CTC number, biomarker expression, and kinetics as prognostic and predictive markers in patients with GI malignancies
Serial ctDNA testing is slow and costly; this AACR 2024 poster tracked CTC number, biomarker expression and kinetics across 44 patients with advanced or metastatic GI cancers to test CTC analysis as a complementary metric or an alternative to ctDNA.
Presented by RareCyte.
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- CTCs were detected in 93% of patients and 86% of samples, with an average turnaround of 5-7 days. Across a cohort of 44 patients with advanced or metastatic GI cancers, CTCs were found in 41 of 44 patients and in 67 of 78 blood samples collected, and average CTC testing turnaround time was 5-7 days.
- Colorectal carcinoma carried the highest baseline average count — and by far the widest spread. It was the largest subtype at 30 of the 44 patients, averaging 72 CTCs per 7.5 mL of blood at the initial baseline draw, yet its median was just 3 and individual counts ran from 0 to 1378; the seven other GI subtypes each averaged 9 CTCs or fewer.
- Changes in CTCs tracked treatment response — and in one patient, moved ahead of cfDNA. Rapid decline or clearance occurred within days of effective systemic therapy starting; in Patient 11, CTC number and Ki67 positivity indicated early response prior to cfDNA mutational burden analysis, which read 23% at baseline, 1.9% at week 9 and 0.5% at week 13. Biomarker status was quantified on the CTCs themselves using dual assays — Ki67/EGFR or PD-L1/HER2.
