Research On Detection And Clinical Significance Of CTC In Peripheral Circulation Of Patients With Esophageal Squamous Cell Carcinoma

BackgroundEsophageal cancer is current the 8th most common malignant cancer and the 6th common cause of cancer-related death globally. There is difference in the prevalence of esophageal cancer between Eastern and Western countries, and the incidence of and mortality rates associated with esophageal adenocarcinoma have become dominant in North America and Europe. In Asian countries, esophageal squamous cell carcinoma(ESCC) account for more than 90% of all cases of esophageal cancer. A major cause of death in ESCC patients is distant metastases, so ESCC patients have poor prognosis and overall 5-year survival rate is less than 30%. It’s difficult for traditional imaging tests and tumor markers to timely find metastasis or recurrence of the tumor.Circulating tumor cells(CTC) in peripheral blood play an important role in tumor metastasis or recurrence. Separating from the primary tumor into the circulatory system for some reason, CTC finally reached the new organization for the development of metastases.Among a series of CTC capture technologies in accordance with the different principle, two main methods have been employed based on either tumor associated marker-dependent and-independent. The representative of former is now relatively mature testing platform Cell Search system, and isolation by size of epithelial tumor cells(ISET) is a detection technology based on different diameters of tumor cells and blood cells to separate CTC/CTMthrough membrane filtration. Recent studies on breast, lung cancer and colorectal cancer confirm that CTC is an independent prognostic factor in patients with cancer and the marker and target of targeted therapy. Monitoring CTC may have important clinical significances on detection of tumor micrometastasis, assessment prognosis, monitoring therapeutic efficacy and so on. Unlike the other malignancies, there had been only a few reports on CTC isolation from the ESCC patients. In Pub Med retrieval system, using the Cell Search system for study of CTC in the ESCC is relatively less, and there is no report on ISET method for CTC study in the research field of the ESCC, and the clinical application value of these two detection methods in the ESCC is unclear.Objective1. To detect and investigate the prevalence of CTC in peripheral blood of patients with ESCC using Cell Search system and ISET method respectively.2. To evaluate the correlation of CTC results with the clinicopathological characteristics, and to discuss the clinical significance of CTC detection in peripheral blood of patients with ESCC.MethodsA total of 61 consecutive patients with primary ESCC at the Shandong Cancer Hospital and Institute from May to December 2014 were enrolled in this prospective study. There were also 22 healthy volunteers as control. After informed consent was obtained for participant in this study and prior to the initiation of treatment, 7.5 ml peripheral blood was drawn via the elbow vein of participants and analyzed by the Cell Search system. Simultaneously 5 ml peripheral blood were detected by the CTC-Biopsy system(ISET method) in the Center Laboratory of Shandong Cancer Hospital and Institute.The χ2analysis or Fisher’s exact test was used to explore the correlation between CTC detected by ISET method and patient’s characteristics. Student’s t-test was used for continuous variables.Results1. The results of CTC in peripheral blood of healthy volunteers using the Cell Search system and the ISET methodNo CTC was found in peripheral blood of 22 healthy volunteers using the Cell Search system and ISET method respectively.2. The results of CTC in peripheral blood of patients with ESCC using the Cell Search system and the ISET method1) In 61 patients with ESCC, using the Cell Search system, CTC was detected in peripheral blood from one patient with IV stage, the CTC detection rate was 1.6%(1/61) in all patients.2) In 61 patients with ESCC, using the ISET method, more than one CTC were detected in 20 patients, the CTC detection rate was 32.8%(20/61) in all patients, according to the pathological stage, the CTC detection rate of I-IV stages were 0.0%(0/4), 30.8%(4/13),31.4%(11/34), 50.0%(5/10) respectively; Circulating tumor microemboli(CTM) were observed in 3 patients, the CTC detection rate was 4.9%(3/61) in all patients, according to the pathological stage, and the CTM detection rate of I-IV stages were 0.0%(0/4), 7.7%(1/13),2.9%(1/34), 10.0%(1/10) respectively.3. Correlation between the presence of CTC and clinicopathological characteristics1) The CTC positive cases using the Cell Search system were too few, so that to sieve out the influential variables.2) Correlation analysis showed that the positive rate of CTC by ISET method was associated with pathological staging. In addition, between patients with positive and negative CTC, the average baseline number of platelets was significant differences(P<0.05). However,clinical features of patients and positive rates of CTC were not significantly correlated with patient age, gender, ECOG, smoking, alcohol consumption, serum CEA, baseline hemoglobin level and neutrophil/lymphocyte ratio(N/L). Also, there was no significant correlation between positive rate of CTC and pathological features, such as tumor location, tumor size,grade of differentiation, tumor depth, lymphatic or venous invasion, the lymph node metastasis.Conclusions1. The specificity of CTC detection by Cell Search system in peripheral blood of ESCC was 100%, but the sensitivity was very low(1.6%). The sensitivity of CTC detection by ISET method in peripheral blood of ESCC was 32.8%(20/61), and the specificity was 100%, so detection of CTC in peripheral blood of patients with ESCC by ISET was feasible.2. Much of the discrepancy of CTC detection rate between Cell Search system and ISET method may be due to the markedly different capture mechanisms used by the two assays.3. To our knowledge, this is the first report of CTM detected in the ESCC research, but CTM were undetectable by Cell Search.4. The result of CTC in peripheral blood of ESCC by ISET method was associated with pathological stage, baseline number of platelets, illustrating the level of CTC may be a useful complement to the more accurate stages of ESCC, and also illustrating the blood-borne metastasis of ESCC may be relevant with pre-treatment thrombocytosis.