Association of complementing circulating tumor DNA and circulating tumor cells load on stable and progressive disease in treated patients.

Abstract

3062 Background: Post curative-intent surgery and therapy, the presence of circulating tumor DNA (ctDNA) load represents Minimal Residual Disease (MRD). Conversely, presence of Circulating Tumor Cells (CTCs) in I-II cancer stage or even in disease free survival (DFS) patients indicates occult Cellular Residual Disease (CRD) with undetectable micro-metastasis. Thus these complementary biomarkers undergoing treatment are the indicators of non-responsiveness outcome suggesting the treatment modifications. Methods: Retrospectively, we monitored a cohort of 46 cancer patients for MRD using ctDNA and CTCs- treated or undergoing treatment (e.g. lung, breast, colon, HNC (n = 14, 7, 6, 4, respectively). OncoMonitor test detected single nucleotide variation (SNVs), small insertions and deletions (INDELs), copy number variations (CNVs), and translocations (fusions). Libraries were prepared using a hybridization-capture method covering 1000 targets with mean sequencing depth 5000X on Illumina Nextseq 2000 in a pair-end mode (150 x2). Variant calling was performed using a proprietary bioinformatics pipeline iCare. CTCs were isolated using the OncoDiscover platform possessing anti EpCAM antibody based immunomagnetic system per 1.5 mL blood. CTCs were confirmed with CK18+, PD-L1 and CD45 using a motorized fluorescence microscope. Results: From ctDNA, 47.82% (n = 22) of patients identified with at least 1 actionable genomic finding. 13.04% (n = 6) patients showed EGFR driver mutations. Also, 19.56% (n = 9) patients were identified with either EGFR driver/KRAS/PI3K passenger mutations with 4.34% (n = 2) identified with ALK-EML4 fusion. The average ctDNA load obtained in patients with progressive disease (n = 26) was 8.2 molecules per 1mL of plasma. At least 1 CTC was detected in 61.53% (n = 16) of progressive disease patients with the highest of 4 CTCs identified in 7.69% (n = 2) of patients. Only 30% (n = 6) of patients with stable disease were identified with at least 1 genomic finding from a total of 20 patients upon ctDNA analysis with an average ctDNA load of 2.2 molecules per 1mL of plasma. Patients with clinically progressive disease showed ctDNA load ~4 fold higher than in patients with stable disease upon treatment. No patients were identified with 4 CTC in the stable disease cohort as opposed to 7.69% in progressive disease patients upon treatment. Conclusions: We observed ctDNA and CTCs complementing MRD status, even post curative-intent surgery and therapy with prophecy for such patients likely to progress. Our findings are strongly indicative of positive correlation between ctDNA load, number of CTC detected, and disease progression from radiological findings for practical and clinical decisions. More studies in this direction are imperative to attain the follow ups for better clinical outcome.