Circulating Tumor Cells Following First Chemotherapy Cycle: An Early and Strong Predictor of Outcome in Patients With Metastatic Breast Cancer

Abstract

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Weinvestigated the prognostic significance of circulating tumor cells (CTCs) determined immediately before the second cycle of chemotherapy in patients with metastatic breast cancer (MBC). The CTC counts were taken at baseline, before the first cycle of chemotherapy (CTC-0) and on day 21 before commencing the second cycle of chemotherapy (CTC-21) in consecutive MBC patients. The study s primary objectives were to analyze relationships between CTC-21 count and overall survival (OS). Based on the current literature, the CTC measurements were dichotomizedas0 4versus 5CTCs.Of117patients recruited,99were evaluable. Patients with 0 4 CTCs on day 21 had a significantly better OS than those with 5 CTCs (median OS: 38.5 months vs. 8.7months).Theyalsohadasignificantly better progression-free survival (PFS; median: 9.4 months vs. 3.0 months) and clinical benefit rate (77% vs. 44%). The OS of patients whose baseline CTCs were 5 but dropped to 5 on day 21 was apparently similar to those who had 5 CTCs at baseline. In a Cox regression analysis, CTC-21 was the only independent variable significantly predicting OS and PFS. Our data indicate that CTCs determined immediatelybeforethesecondcycle ofchemotherapyisanearly andstrong predictor of treatmentoutcomeinMBCpatients. The Oncologist2013;18:000 000