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e14558 Background: PD-1/PD-L1 checkpoint blockade immunotherapy is revolution- izing the therapeutic strategy of malignancies. Tumor PD-L1 levels have predictive value in PD-1/PD-L1 checkpoint blockade therapies. Whether PD-L1 expression on circulating tumor cells (CTCs) could serve as an alternative biomarker is of great interest, especially in breast cancer. Methods: We established an immunofluorescence assay for semi-quantitative assessment of the PD-L1 expression levels on CTCs with four categories (PD-L1negative, PD-L1low, PD-L1medium and PD-L1high). 20patients with advanced breast cancerwere enrolled who took PD-1 inhibitortherapy. The CTC numeration and the PD-L1 expression levels were analyzedat the begining and ending of treatment . Results: 20 patients were enrolled, 85%(17/20) were triple-negative breast cancer. 65% of patients had visceral metastases, 60% of patients had ≥3 lines of treatment. Prior the treatment of PD-1 inhibitor, 95% (19/20) patients had CTCs, ranging from1 to 53(median 5). 90% (18/20) had PD-L1positive CTCs, and 75% (15/20) had at least one PD-L1high CTCs. The clinical benefit rate(CBR) rate in PD-L1high patients (26.7%) is much higher than the others (0%). we examined the proportion of PD-L1high CTCs relative to total CTCs. The median proportion of PD-L1high CTCs was 33.3%. Patients with ≥33% PD-L1high CTCs had a significantly longer PFS (median 2.6 vs. 1.4 months( P = 0.027). 100% patients with CBR had PD-L1highCTCs decreased and 46.7% of patients without CBR decreased. Further analysis showed that the mean proportion of PD-L1highCTCs at baseline and after treatment was 56.8±20.7%, 19.0±23.7%, p = 0.005. There was no significant difference in the mean proportion of PD-L1highCTCs before and after treatment in the non-CBR group (28.0±26.2%, 30.3±31.5%, p = 0.846). Conclusions: We revealed that the abundance of PD-L1high CTCs at baseline might serve as a predictor to screen patients for PD-1/PD-L1 blockade therapies and measuring the dynamic changes of PD-L1high CTCscould indicate the therapeutic response at early time.

e12084Background: Circulating tumor cell (CTC) and serum HER2 ECD can reflect tumorous biological information in different aspects, however their clinical significance for HER2-positive advanced breast cancer receiving anti-HER2 therapy remain unclear. We performed this prospective, monocenter, double-blinded study to investigate the potential clinical significance of detection of CTC and serum HER2 ECD for advanced breast cancer patients with histological HER2-positivity. Methods: A total of 155 eligible patients were enrolled in the present study from April 2012 to October 2015. We used Cell search system and ADVIA Centaur System to detect CTC and serum HER2 ECD respectively. Patients received systemic treatment according to national and international guidelines. Results: Forty nine (31.6%) patients had ≥ 5 CTC, One hundred and twenty three (79.4%) patients had serum HER2 ECD values of at least 15ng/ml, forty seven (30.3%) patients had both elevated CTC and ECD values, thirty (19.4%) patients had both n...

e12006 Background: The percentage of breast cancer patients exposed to anthracyclines and taxanes in the adjuvant or neoadjuvant chemotherapy is increasing, in metastatic stage using again is limit...