RESUMO
Background: Circulating tumor cells (CTCs) play an important role in progression and metastasis, particularly in form of cluster, which is called circulating tumor microemboli (CTM), and can be found in the peripheral blood of cancer patients. The aim of this study was to evaluate the presence of CTCs and CTM, and its influence on tumor progression in lung cancer patients. Methods: CTCs were isolated by Isolation by Size of Epithelial Tumor cells (ISET®) Technology. The samples of metastatic lung cancer patients were collected before the beginning of systemic chemotherapy. CTCs and CTM were identified according to their morphological features. Results: Fifteen patients were analyzed. Patients who had CTM in blood previously the beginning of systemic therapy had poor progression-free survival (PFS) compared to those with absence of CTM, although without statistical significance (median PFS 3.1 months × 6.7 months, p = 0.29). Moreover, patients without any prior treatment had less than 3 CTCs/mL compared to patients previously exposed to chemotherapy, who had 3 CTCs/mL or more (p = 0.31). Additionally, these patients, with prior treatment, showed poor PFS, compared to chemo-naive patients, although without statistical significance (mean PFS: 4.6 months × 7.3 months, p = 0.47). Conclusions: We identified, even in a limited number of samples, that an elevated baseline levels of CTCs and the presence of CTM were associated with poor prognosis in patients with metastatic lung cancer. In addition, we showed that an increase of CTCs counts could indicate a pre-existing resistance. However, further studies with a large cohort are needed to support this information