Circulating tumor cells at each follow-up time point during therapy of metastatic breast cancer patients predict progression-free and overall survival

Purpose: We reported previously that >= 5 circulating tumor cells (CTC) in 7.5 mL blood at baseline and at first follow-up in 177 patients with metastatic breast cancer (MBC) were associated with poor clinical outcome. In this study, additional follow-up data and CTC levels at subsequent follow-up visits were evaluated. Experimental Design: CTCs were enumerated in 177 MBC patients before the initiation of a new course of therapy (baseline) and 3 to 5, 6 to 8, 9 to 14, and 15 to 20 weeks after the initiation of therapy. Progression-free survival (PFS) and overall survival (OS) times were calculated from the dates of each follow-up blood draw. Kaplan-Meier plots and survival analyses were done using a threshold of >= 5 CTCs/7.5 mL at each blood draw. Results: Median PFS times for patients with <5 CTC from each of the five blood draw time points were 7.0, 6.1, 5.6,7.0, and 6.0 months, respectively. For patients with >= 5 CTC, median PFS from these same time points was significantly shorter: 2.7,13,11.4, 3.0, and 3.6 months, respectively. Median OS for patients with <5 CTC from the five blood draw time points was all >18.5 months. For patients with >= 5 CTC, median OS from these same time points was significantly shorter: 10.9, 6.3, 6.3, 6.6, and 6.7 months, respectively. Median PFS and OS times at baseline and up to 9 to 14 weeks after the initiation of therapy were statistically significantly different. Conclusions: Detection of elevated CTCs at any time during therapy is an accurate indication of subsequent rapid disease progression and mortality for MBC patients.