Circulating Tumor Cell Subtypes may Predict Responses to Neoadjuvant Chemotherapy in Locally Advanced Breast Cancer

Background: Neoadjuvant chemotherapy (NCT) is the standard treatment for patients with locally advanced breast cancer (LABC). However, the predictive value of circulating tumor cells (CTCs) with different molecular subtypes in NCT response has not yet been determined, which was, therefore, the aim of this study. Methods: All patients were staged as LABC and received an EC×4 –T×4 NCT regimen. Blood samples were collected from patients at the time of biopsy, and after the first and eighth NCT courses. Patients were divided into High responders (High-R) and Low responders (Low-R) according to Miller-Payne system and changes in Ki-67 levels after NCT treatment. A novel SE-i•FISH strategy was applied to detect CTCs. Subtypes were successfully analyzed in LABC patients undergoing NCT, for the first time. Results: Total CTCs increased continuously and were higher for Low-R patients; while in the High-R group, total CTCs increased slightly during NCT before returning to baseline levels. Triploid and tetraploid chromosome 8 as well as the proportion of each, increased for Low-R but not High-R patients. The number of small CTCs in the Low-R group increased significantly until the last sample, however, remained constant in the High-R group. The patients with more CTCs had shorter PFS and OS than those with less CTCs after the 8th course of NCT. Conclusions: Total CTCs as well as individual subtypes within peripheral blood following NCT were predictive of patient responses to NCT. More detailed characterization of CTC blood profiles may improve predictive capacity and lead to improved LABC treatments.