Chemotherapy plays an important role in the treatment of metastatic breast cancer. It is important to monitor chemotherapeutic efficacy, to find a simple and efficient tool to guide treatment, and to predict the efficacy of treatment in a timely and accurate manner. This study aimed to detect mucin-1 (MUC1)– positive circulating tumor cells and MUC1 protein in the peripheral blood of patients with metastatic breast cancer and to investigate their relationship to chemotherapeutic efficacy. MUC1 mRNA was detected in the peripheral blood of 34 patients with newly diagnosed metastatic breast cancer by reverse transcription-polymerase chain reaction. The positive rates of MUC1 mRNA were 88.2% before chemotherapy and 70.6% after chemotherapy, without a significant difference (P = 0.564); MUC1 mRNA expression before chemotherapy had no correlation with treatment effectiveness (P = 0.281). The response rate of MUC1 mRNA-negative patients after first-cycle chemotherapy was significantly higher (P = 0.009) and the progression-free survival (PFS) was clearly longer than those of MUC1 mRNA-positive patients (P = 0.095). MUC1 protein in peripheral blood plasma was detected by an ELISA competitive inhibition assay. The patients with decreased MUC1 protein after chemotherapy had a significantly longer PFS than those with elevated MUC1 protein (P = 0.044). These results indicate that the outcomes of MUC1 mRNA-negative patients after chemotherapy are better than those of MUC1 mRNA-positive patients. In addition, patients with decreased expression of MUC1 protein have a better PFS.

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Objective:The purpose of this study is to explore RT-PCR method to set up the examination platform for detecting circulating tumor cells (CTC) in peripheral blood from metastatic breast cancer patients. The primary endpoint is to find out the correlation of existence of CTC with clinical responses and progression-free survival (PFS).Methods: The breast cancer cell line MCF-7 was serially diluted into the peripheral blood from 45 healthy donors to set up the sensitivity of RT-PCR assay. The expression of CK19 mRNA was amplified from both 49 patients and 45 healthy donors respectively. The CK19 protein quantity from plasma was measured by competitive inhibition ELISA assay.Results: The sensitivity of RT-PCR could reach 1/10 6 −10 7 white blood cells with specificity of 95.6%. The objective response rate (ORR) of patients with CK19 mRNA-negative undertaken one cycle chemotherapy was significantly higher than those with positive (P<0.0001). PFS among CK19 mRNA-negative patients was also increased, although there was no significance (P=0.098). The results of ELISA assay showed that CK19 protein was decreased significantly after one cycle chemotherapy, which gave rise to a little higher ORR (P=0.015) and increased PFS (P=0.016).Conclusion: Patients with unamplified CK19 mRNA after one cycle chemotherapy could achieve better radiographic evaluation and increased PFS, which was showed to be of consistency with the CK19 protein assay among the patients treated.

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