Circulating Tumor Cells versus Imaging—Predicting Overall Survival in Metastatic Breast Cancer

Interreader variability for radiologic responses and CTC counts were 15.2% and 0.7%, respectively. The median overall survival of 13 (9%) patients with radiologic nonprogression and >or=5 CTCs was significantly shorter than that of the 83 (60%) patients with radiologic nonprogression and or=5 CTCs that showed progression by radiology (19.9 versus 6.4 months; P=0.0039).

Assessment of CTCs is an earlier, more reproducible indication of disease status than current imaging methods. CTCs may be a superior surrogate end point, as they are highly reproducible and correlate better with overall survival than do changes determined by traditional radiology.