Prognostic value of circulating tumor cells in advanced gastric cancer patients receiving chemotherapy

The identification of circulating tumor cells (CTCs) may provide important prognostic information in several types of solid tumors, including gastric cancer. The aim of this study was to investigate whether CTC count may be used to predict survival in patients with advanced gastric cancer treated with chemotherapy. The CELLection (TM) Epithelial Enrich kit was used to isolate and purify CTCs from samples of peripheral blood. Immunofluorescent staining was used for CTC counting. High CTC counts were associated with poor tumor differentiation and high serum CEA levels (P=0.021 and 0.005, respectively). After 3 months, 16 patients with decreasing CTC counts after the first cycle of chemotherapy obtained complete response, partial response or stable disease, while 13 patients with increasing CTC counts developed progressive disease. The patients with decreasing CTC counts also exhibited longer progression-free survival (PFS) (P <= 0.001) and overall survival (OS) (P=0.002) compared with those with increasing CTC counts. Among all 59 patients, those with a CTC count of <= 2 cells/5 ml blood exhibited longer PFS (P <= 0.001) and OS (P <= 0.001) compared with those with a CTC count of >2 cells.5 ml blood. The multi-variate analysis suggested that an increase of the CTC count after the first cycle of chemotherapy was only an independent prognostic marker of poor PFS (P=0.019). However, a baseline CTC count of >2 cells.5 ml blood was an independent poor prognostic marker for PFS (P=0.008) and OS (P=0.001) in all 59 patients. Our study suggested that patients with a low baseline CTC count or decrease of the CTC count after the first cycle of chemotherapy may benefit significantly from palliative chemotherapy. In conclusion, CTC count may be a good chemotherapy monitoring marker and an ideal prognostic marker for patients receiving palliative chemotherapy.