Abstract P2-10-26: Association between circulating tumor cells and molecular breast cancer subtypes

Abstract Background and Objective: Circulating tumor cells (CTCs) provide crucial information for the management of breast cancer patients. CTCs analysis can be used as a liquid biopsy approach for prognostic and predictive purposes in breast and other cancers. Several contradictory results presented about the breast cancer subtypes of CTCs recently. The aim of this study was therefore to analysis the association between the CTCs and molecular breast cancer subtypes. Methods: Blood samples were obtained from 143 breast cancer patients admitted to Breast Surgery Department, Affiliated Hospital of Medical College, Qingdao University. CTCs were detected by using immunomagnetic enrichment and a commercial kit, based on RT-PCR, was used to characterize CTCs. The expression of ER, PR, HER2 was detected by immunohistochemistry. The molecular subtypes were defined as: luminal A (ER+ and/or PR+, HER2−), luminal B (ER+ and/or PR+, HER2+), TNBC (ER−, PR−, HER2−), and HER2+, (ER−, PR−, and HER2+). The relations between the positive rate of CTCs and clinicopathological characteristics of primary tumor and molecular subtypes of breast cancer patients were analyzed. Results: Overall positive rate of CTCs was 39.8% (57/143). The positive rate of CTCs in patients with Luminal A, Luminal B, HER2+ and TNBC subtype was 33.8% (26/77), 47.1% (8/17),50.0% (6/12) and 45.9%(17/37). There was significant difference in positive rate of CTCs by different molecular subtypes (P = 0.0415), especially at different AJCC stages (P = 0.004). The positive rate of CTCs in patients with Luminal A subtype was significantly lower than patients with the others breast cancer subtypes (p = 0.0387). Conclusion: Our study suggests that presence of CTCs was more frequently found in patients with HER2+ and Luminal B subtypes. The presence of CTCs in patients with TNBC subtype was not as high as we wished. Theoretically, the positive rate of CTCs in TNBC subtype should be higher than that of others subtypes for being more aggressive histologically features and having increased potential to be invasive. One possible explanation for this might because of lacking epithelial markers expression and epithelial-mesenchyme transition (EMT) characteristics, CTCs of TNBC subtype are missed when using the standard EpCAM-based method. Shortage of patient's number was another possible reason. Further research on the Association between CTCs and molecular breast cancer subtypes will contribute to a better understanding of the biology of metastatic development in cancer patients. Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P2-10-26.