Incidence and initial characterization of circulating tumor cells in different cancer entities.

Abstract

e21083 Background: Circulating tumor cell (CTC) quantification has been approved for monitoring of blood from metastatic breast, colon and prostatic cancer patients. In other cancers little is known about the presence of CTCs. CTCs might represent a potential alternative to invasive biopsies and assessment of their receptor profile may be helpful in planning and monitoring treatment strategies. This study was undertaken to investigate prevalence and characteristics of CTCs in a variety of solid tumors. Methods: After informed consent, fifty consecutive 20 mL-peripheral blood samples were collected from 38 patients with different metastatic epithelial cancers (n = 30) or metastatic melanoma (n = 8). After lysis of erythrocytes, cells were enriched for tumor cells by CD45 depletion. Cells were stained for CD45 to exclude leukocytes from the analysis and for the epithelial markers EpCAM and Cytokeratin 7, 8 or the melanoma marker HMW-MAA/MCSP, respectively. In 16 samples from patients affected by epithelial cancers a co-staining for EGFR was carried out. Control tubes including appropriate isotypic controls were added. Cells were analysed on a FACSCanto II. CTCs were defined EpCAM+Cytokeratin+CD45- in case of epithelial cancers or as HMW-MAA/MCSP+CD45- in case of melanoma. Results: In blood from patients with epithelial cancers CTCs were detected in 20/40 samples (50%). The absolute number of CTCs ranged from 2 to 37 (median 3) per 10 mL of blood. Besides breast cancer (5/9) and colon cancer (3/11) samples, CTCs were also detected in ovarian (4/8), cervix (2/4), head and neck (3/3), gastric (2/3) and non-small cell lung cancer (1/2) samples. In ten out of 16 samples (62.5%) CTCs were positive for EGFR (4 breast cancer, 2 head and neck, 2 ovarian, 1 gastric and 1 cervix cancer sample). In blood from melanoma patients CTCs were detected in 6/10 samples (60%). The absolute number of CTCs ranged from 5 to 551 (median 19) per 10 mL of blood. Conclusions: CTCs can often be detected in blood from patients with metastatic epithelial cancer or melanoma. CTCs were more abundant in melanoma compared to epithelial cancers. Phenotypic characterization identified EGFR as potential target to eradicate the EGFR-positive pool of CTCs. Author Disclosure Employment or Leadership Position Consultant or Advisory Role Stock Ownership Honoraria Research Funding Expert Testimony Other Remuneration Merck Serono Merck Serono Merck Serono