Circulating Tumor Cells
Circulating tumor cells (CTC) are cancer cells that have become separated from a solid tumor site and are circulating in the bloodstream. The level of circulating tumor cells can be measured from a blood specimen in patients with metastatic breast, colon, or prostate cancer. Measuring CTC can provide information for assessing disease status as well as a patient’s prognosis, thereby providing recommendations for each patient’s individual care.1-3 The CTC assay is FDA-cleared for metastatic breast, prostate, and colon cancers. CTC measurements may have utility for clinical trials in a number of areas including service as a surrogate marker for clinical outcome and for additional assays on the CTC specimen (e.g., RT-PCR).
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Clinical Relevance
- Detecting CTC in a patient’s blood helps the clinician understand the patient’s likely prognosis as well as overall survival rate. Patients with high CTC counts generally have a poor prognosis. (≥ 5 for breast, prostate ≥ 3 for colon)
- Measuring CTC provides information about a patient’s prognosis, both before and after the initiation of therapy.
- Evaluating CTC in breast cancer patients provides prognostic information similar to imaging and predicts survival at least as well as serial radiographic assessment; it is also more reproducible than radiologic evaluation.
- Enumerating CTC provides clinicians with information that may help them develop individualized therapy strategies for their patient.