Assessment of circulating tumor cells in breast cancer patients undergoing neoadjuvant chemotherapy

Abstract

10079 Background: Circulating tumor cells (CTCs) are a valuable prognostic factor in metastatic breast cancer, suggesting that CTCs, if present, may be clinically useful in other breast cancer (BC) settings. This study prospectively evaluated CTCs before and after neoadjuvant chemotherapy (NACT) in patients with operable breast cancer. Methods: 7.5 or 30ml of blood were drawn in CellSave tubes from 26 Pts about to receive NACT (docetaxel + capecitabine followed by adriamycin + cytoxan) followed by surgery. CTC analysis is being performed at multiple time points. Data presented are from baseline (prior to first dose), post-NACT, and 3 months after surgery. CTCs were measured by immunomagnetic separation and automated fluorescent microscopy using the CellSearch System (Veridex/Immunicon Corp). Results: Baseline CTCs: For the first 11 pts CTCs were analyzed from 7.5ml of blood. 36% (4/11) had ≥1 CTC, 27% (3/11) had ≥2 CTCs. Of pts with detectable CTCs, the mean was 2.75 CTCs/7.5ml (range 1–4). To improve baseline sensitivity, 30ml blood was drawn from the subsequent 15 pts. One sample was not evaluable. 50% (7/14) had ≥1 detectable CTC and 29% (4/14) had ≥2 CTCs. Of pts with detectable CTCs, the mean was 3.0 CTCs/30ml (range 1–10). CTCs post-neoadjuvant therapy: All 26 pts had 30ml of blood drawn for CTC analysis. 27% (7/26) had ≥1 CTC, and 8% (2/26) had ≥2 CTCs. Using as threshold of ≥2 CTCs to define elevated, CTCs post-chemotherapy were compared to the pathologic complete response (pCR). Sensitivity was 10% (2 of 18 pts with residual disease had elevated CTCs). Specificity was 100% (0 of 7 pts with a pCR had elevated CTCs). This correlated to a positive predictive value of 100% and a negative predictive value (NPV) of 28%. CTCs 3 months after surgery: Of 21 pts analyzed, only one pt (5%) had a single CTC. Long-term follow-up blood collection is ongoing. Conclusions: CTCs are detectable in ∼30% locally advanced BC. All patients with CTCs after NACT had residual disease at surgery, and no CTCs were detected in patients with pCR. However, the absence of CTCs after NACT did not predict pCR. Pts will be followed to determine if CTCs correlate with recurrence and survival. [Table: see text]