Abstract 1569: Circulating tumor cells and circulating tumor microemboli in the context of gastric adenocarcinoma

Background: Whereas the pathological aspects of Gastric Adenocarcinomas (GAC) are well defined, there is still an important lack of biomarkers predictive of its occurrence, aggressiveness and response to neoadjuvant treatment. Nowadays, it is known that isolated or clustered Circulating Tumor Cells (respectively CTCs or CTMs, for Microemboli) can be found in the blood of patients many months before tumor detection. In this sense, the identification of CTCs/CTMs in GAC patients has a potential value as biomarkers for tumor growth and invasiveness. Objective: to study the predictive value of CTCs and CTMs from GAC patients, evaluating their presence and correlation with HER2-status and clinical-pathological characteristics. Methods: Blood was prospectively collected from 72 GAC patients (62.5% men) recruited at the Department of Abdominal Surgery of the A.C.Camargo Cancer Center, São Paulo, Brazil, from March 2016 to March 2017, after the signature of informed consent forms previously approved by the institutional review board. Blood was first collected before the first neoadjuvant cycle (at diagnosis) and also before adjuvant treatment (diagnosis of metastasis). The samples were processed and filtered in ISET (Rarecells, France) allowing the isolation and quantification of CTCs and CTMs, and immunocytochemistry (ICC) with anti-HER2. Results: The most common tumor status were T1b (15/20.8%) and N1 (14/19.4%) and diffuse tumors (Lauren's) was the most common subtype (37/51.4%); 55 patients had non-metastatic disease (76.4%) at moment of inclusion. CTCs were found in 61/72 patients (84.7%) with a median of 2.5 CTCs/mL (0-39.6 CTCs/mL). We found more CTC/mL in non-metastatic disease (2.8 CTCs/mL versus 0.9 CTCs/mL, p