Prevalence and quantity of circulating tumor cells (CTCs) after adjuvant chemotherapy in patients with HER2-negative early breast cancer (EBC).

Abstract

e22075 Background: Prevalence of CTCs after adjuvant chemotherapy in patients with EBC might indicate both treatment response and prognosis. Here we present data on CTC prevalence and quantity assessed after chemotherapy in correlation with tumor characteristics and chemotherapeutic treatment in patients with Her2-negative EBC from the German SUCCESS C study. Methods: The SUCCESS C trial is a randomized, open-label, Phase III study comparing disease free survival (DFS) in patients with HER2-negative EBC treated with either 3 cycles of Epirubicin-Fluorouracil-Cyclophosphamide(FEC) followed by 3 cycles of Docetaxel(DOC), or 6 cycles of a anthracycline-free regimen with Docetaxel-Cyclophosphamide(DOC-C). The CTC status at chemotherapy cycle 6 was prospectively evaluated using the FDA-approved CellSearch System (Veridex, USA). Results: Valid data on CTC status after chemotherapy were available for 2,336 patients (78% estrogen receptor positive, 6% pT3 or pT4, 12% pN2 or pN3). CTCs were found in 278 (11.9%) patients (median 1, range 1 – 69 CTCs). One CTC was detected in 164 (59%), two CTCs in 57 (21%), three to five CTCs in 45 (16%), and more than five CTCs in 12 (4%) of these patients. CTC prevalence was not significantly associated with tumor size (pT1, pT2, pT3, pT4), nodal stage (pN0, pN+), grading (G1, G2, G3), histological type (invasive ductal, invasive lobular, other), estrogen receptor status, progesterone receptor status, or treatment arm (FEC-DOC, DOC-C), as revealed by both univariate analyses (Chi-square tests, all p > 0.1) and a logistic regression with CTC prevalence as dependent variable. Conclusions: In about 12% of patients with Her2-negative EBC, CTCs in the peripheral blood were detected at the end of adjuvant chemotherapy treatment. However, neither CTC prevalence nor quantity of CTCs were related to tumor characteristics or type of chemotherapeutic regimen. The low rate of CTC-positive patients might be attributed to the negative HER2 status and reflects therefore the relatively low risk of these patients to develop metastatic relaps. Clinical trial information: NCT00847444.