The Potential Clinical Implications of Circulating Tumor Cells and Circulating Tumor Microemboli in Gastric Cancer

Abstract

Background: Gastric adenocarcinoma (GAC) is the third deadliest malignant neoplasm worldwide, mostly because of late disease diagnosis, low chemotherapy response rates, and an overall lack of tumor biology understanding. Therefore, tools for prognosis and prediction of treatment response are needed. Quantification of circulating tumor cells (CTCs) and circulating tumor microemboli (CTM) and their expression of biomarkers has potential clinical relevance. Our aim was to evaluate CTCs and CTM and their expression of HER2 and plakoglobin in patients with nonmetastatic GAC, correlating the findings to clinicopathological data.

Materials and methods: CTC enrichment was performed with isolation by size of epithelial tumor cells, and the analysis was performed with immunocytochemistry and microscopy. Two collections were made: one at diagnosis (55 samples before neoadjuvant treatment) and one after surgery and before adjuvant therapy (33 samples).

Results: A high detection rate of CTCs (90%) was observed at baseline. We evaluated HER2 expression in 45/55 biopsy samples and in 42/55 CTC samples, with an overlap of 36 subjects. Besides the good agreement observed for HER2 expression in primary tumors and paired CTCs for 36 cases (69.4%; κ = 0.272), the analysis of HER2 in CTCs showed higher positivity (43%) compared with primary tumors (11%); 3/5 patients with disease progression had HER2-negative primary tumors but HER2-positive CTCs. A significant CTC count drop in follow-up was seen for CTC-HER2-positive cases (4.45 to 1.0 CTCs per mL) compared with CTC-HER2-negative cases (2.6 to 1.0 CTCs per mL). The same was observed for CTC-plakoglobin-positive cases (2.9 to 1.25 CTCs per mL).

Conclusion: CTC analysis, including their levels, plakoglobin, and HER2 expression, appears to be a promising tool in the understanding the biology and prognosis of GAC.

Implications for practice: The analysis of circulating tumor cell levels from the blood of patients with gastric adenocarcinoma, before and after neoadjuvant treatment, is useful to better understand the behavior of the disease as well as the patients more likely to respond to treatment.

Keywords: Circulating tumor cells; Circulating tumor microemboli; Gastric adenocarcinoma; HER2; Plakoglobin.

Conflict of interest statement

Disclosures of potential conflicts of interest may be found at the end of this article.

© AlphaMed Press 2019.

Figures

Figure 1.

Flow chart of patients enrolled in this study. 55 patients with gastric cancer were included before the beginning of neoadjuvancy (baseline); 73.8% of them received FOLFOX or XELOX‐based chemotherapy; 94.5% of all patients was submitted to surgical procedure. The follow‐up was made for 33 patients before the beginning of adjuvant chemotherapy, where FOLFOX and XELOX were also more commonly used (77.4%). The median time between baseline and follow‐up was 2.7 months (minimum 1.78 and maximum 4.84 months). Abbreviations: CF/XP, cisplatin and 5‐fluorouracil or cisplatin and capecitabine; FOLFOX, folinic acid, 5‐fluorouracil and oxaliplatin; GC, gastric cancer; XELOX, capecitabine and oxaliplatin.

Figure 2.

PFS analysis of patients with nonmetastatic gastric cancer in relation to isolated CTCs and CTM at baseline. (A): Patients with the count of CTCs above 2.8 per mL versus those with count of CTCs under 2.8 per mL: median PFS not achieved for both (p = .103). (B): Patients with CTM presence had poor mean PFS in relation to those with CTM absence (18.7 months vs. 21.6 months, respectively; p = .258). Abbreviations: CTCs, circulating tumor cells; CTM, circulating tumor microemboli; PFS, progression‐free survival.

Figure 3.

PFS analysis of patients with nonmetastatic gastric cancer in relation to the expression of HER2 protein in isolated CTCs, and plakoglobin protein in CTM at baseline. (A): Patients with HER2‐positive CTCs and patients with HER2‐negative CTCs: median PFS not achieved for both (p = .092). (B): Patients with plakoglobin‐positive CTM and patients with plakoglobin‐negative CTM: 16.3 months versus not achieved, respectively (p = .114). (C): Patients with diffuse histological subtype evaluated for HER2 in CTCs and plakoglobin in CTM: patients with both proteins negative had better PFS than patients with one or the other positive (PFS not calculated; p = .027). Abbreviations: CTCs, circulating tumor cell; CTM, circulating tumor microemboli; HER2, human epidermal growth factor receptor 2; PFS, progression‐free survival.

Figure 4.

Immunostaining of CTCs and CTM from patients with gastric cancer. (A, B): CTCs visualized with hematoxylin‐eosin (×40). (C): CTM visualized with hematoxylin‐eosin (×40). (D): CTC stained with anti‐HER2 antibody, visualized with DAB, and counterstained with hematoxylin‐eosin (×40). (E): CTC stained with antiplakoglobin antibody, visualized with DAB, and counterstained with hematoxylin‐eosin (×40). (F): CTM stained with antiplakoglobin antibody, visualized with DAB, and counterstained with hematoxylin‐eosin (×20). All images were analyzed on Research System Microscope BX61 (Olympus) coupled to a digital camera (SC100; Olympus). Abbreviations: CTCs, circulating tumor cells; CTM, circulating tumor microemboli; DAB, diaminobenzidine; HER2, human epidermal growth factor receptor.