It has been estimated for 2012, 73,420 diagnoses of Colorrectal Cancer (CCR) for men and 70,040 for women, representing, in both genders, the third most common type of cancer, and 9% of all cancer cases in the USA. It is believed that the spread of cancer requires the presence of circulating tumor cells (CTCs), which are rare cells surrounded by billions of hematopoietic cells in the bloodstream; thus, the isolation of these cells is a potential strategy for development clinician with non-invasive methods. The primary detection of CTCs may help identify patients in need of additional systemic therapy after surgical resection of the primary tumor. Despite all the therapies being developed to prevent metastatic relapse, the patient selection is based on statistical risk of developing recurrence, without actually knowing if they harbor any CTC. This leads to over treatment of these patients with toxic agents that induce severe side effects. This study aims to: 1) detect CTCs in the peripheral blood of patients with metastatic colorectal cancer and to correlate its levels with imaging and overall survival, progression-free and recurrence-free, 2) verify if the levels of CTCs decrease after chemotherapy; 3) evaluate the correlation between the expression of MRP5 carrier and the drug resistance genes (ERCC1, TS, KRAS) in CTCs; 4) establish counting system of CTCs and analysis that can be safely used in clinical practice. It will be analyzed samples from approximately 100 patients. The counting and analysis of CTCs will be performed using MACS system (Carcinome Cell Enrichment and Detection Kit, Miltenyi Biotec, Germany) at three different moments, before the start of chemotherapy and every two months, using 8 mL of blood. At first will additional 8 mL of blood will be collected in a filtration membrane at the ISET device, and this membrane will capture those antigenes and antibodies chosen by the researcher. We will perform the analysis on custom built immunohistochemical tissue microarray (TMA), which will evaluate the expression of the following proteins: MRP5, ERCC1, TS and KRAS. All reactions will have a negative control (blood of healthy individuals) and positive control (the same blood plus colon tumor cells maintained in culture). In the period May '12 to March '13, 28 patients with a diagnosis of cancer of the colon and /or rectum were analyzed. The chi-square method was used to correlate the number of CTCs with: Stadium, TNM, and PFS. The correlation with significant result was the "N" (regional lymph node metastasis), where five patients (62.5%) with <27 CTCs presented as N: 2 and seven patients (63.6%) presented with e 27 CTCs N: 0 in the first test (p = 0.04).
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