Circulating Tumor Cells: Beyond Isolation and Detection

Abstract

Circulating tumor cells (CTCs) are the precursors to metastases and increased numbers of CTCs in the peripheral circulation 
have been shown to correlate with decreased progression-free and overall survival. Although the current clinical utility has been 
focused on the prognostic significance, other clinical applications are being explored, such as determining if a patient is a candidate 
for treatment, determining the efficacy of treatment, evaluation for resistance to therapy, prediction of metastatic site, or as an 
early predictor of metastases. Current methodologies are based on quantifying CTCs and include technologies based on physical, 
immunological, and molecular techniques. However, these have limitations, of which most of them do not have the ability to 
perform morphological evaluation. Using morphological evaluation, CTCs in body fluids could be used for primary diagnosis in 
the setting of cancer of unknown primary (CUP) or in initial or early diagnostic scenarios. Additionally, cytological specimens have 
been shown to be useful for ancillary testing in patients when surgical resection specimens or biopsies are not available. Evaluation 
of CTCs should incorporate histological, immunehistochemical, and molecular characterization to enable clinicians to obtain the 
comprehensive diagnostic, prognostic and therapeutic information necessary to provide appropriate personalized care to cancer 
patients