ERBB2 and metastatic neoplasm: Regardless of histology, hormone receptor and HER2/neu status, or whether the patient had recurrent or de novo metastatic disease, those with <5 CTCs at baseline, and more importantly, at first follow-up after beginning a new treatment regimen, had superior progression free (PFS) and overall survival (OS) (7 vs 2.1 months [p < 0.001] and 10.1 vs >18 months, [p < 0.001], respectively).