Prevalence of Circulating Tumor Cells After Adjuvant Chemotherapy With or Without Anthracyclines in Patients With HER2-negative, Hormone Receptor-positive Early Breast Cancer

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Abstract

Background

Use of anthracycline-based chemotherapy in patients with early breast cancer (EBC) has been well-established but is often associated with cardiotoxicity. Based on data suggesting a limited benefit of anthracyclines in human epidermal growth factor receptor 2 (HER2)-negative patients, the Simultaneous Study of Docetaxel Based Anthracycline Free Adjuvant Treatment Evaluation, as well as Life Style Intervention Strategies (SUCCESS) C study randomized patients to either anthracycline-containing or anthracycline-free chemotherapy. Given the proven prognostic value of circulating tumor cells (CTCs) in EBC, we compared the prevalence of CTCs after chemotherapy between both treatment arms for a preliminary efficacy assessment.

Methods

The SUCCESS C trial (NCT00847444) is an open-label, phase III study randomizing 3547 patients with HER2-negative EBC to either 3 cycles of epirubicin, 5-fluorouracil, and cyclophosphamide followed by 3 cycles of docetaxel (FEC-DOC) or 6 cycles of docetaxel and cyclophosphamide (DOC-C). CTC status was prospectively evaluated in hormone receptor-positive patients at the time of last chemotherapy cycle using the US Food and Drug Administration-approved CellSearch System (Janssen Diagnostics).

Results

Data on CTC status were available for 1766 patients. Overall, CTCs were found in 221 (12.5%) patients. Univariate analyses revealed that presence of CTCs at time of last chemotherapy cycle was not significantly associated with tumor or patient characteristics (all P > .1). There was no significant difference with respect to presence of CTCs between patients randomized to FEC-DOC or DOC-C (11.5% vs. 13.6%; P = .18).

Conclusions

The comparable prevalence of CTCs at the time of last chemotherapy cycle may indicate that anthracycline-free chemotherapy is equally effective to anthracycline-containing chemotherapy in HER2-negative, hormone receptor-positive EBC. However, efficacy data from the final survival analysis of SUCCESS C have to be awaited to confirm these preliminary findings.

Micro-Abstract

The prevalence of circulating tumor cells (CTCs) in patients with human epidermal growth factor receptor 2-negative, hormone receptor-positive early breast cancer after adjuvant chemotherapy was compared between anthracycline-free and anthracycline-containing treatment cohorts within the Simultaneous Study of Docetaxel Based Anthracycline Free Adjuvant Treatment Evaluation, as well as Life Style Intervention Strategies (SUCCESS) C trial and showed no significant difference. Though CTCs have been established as an early treatment monitoring tool, comparison of CTC prevalence after therapy may have clinical implications with respect to equal effectiveness of both treatment regimens.

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