Circulating tumor cells (CTCs) are cells that have detached from a primary tumor and circulate in the bloodstream. Whetehr these cells are viable and can establish metastatic foci or whether they can serve a predictors of metastatic disease has and is still being studied. The U.S. Food and Drug Administration (FDA) only cleared the Cell Search (other available systems are AdnaTest BreastCancer® and OncoQuick™ ) system.and it appears to be able to serve as a strong prognostic factor for overall survival in patients with metastatic breast, colorectal or prostate cancer. What is not as clear is how to use this information clinically. Guidelines had not been supportive. In their 2007 update, ASCO made the following recommendations regarding testing for circulating tumor cells (CTCs) in breast cancer (Harris, et al., 2007):
• The measurement of CTCs should not be used to make the diagnosis of breast cancer or to influence any treatment decisions in patients with breast cancer.
• The use of CellSearch Assay in patients with metastatic breast cancer cannot be recommended until additional validation confirms the clinical value of this test.
• There are no data yet generated to prove that the use of CTCs testing will lead to a longer survival time or improved quality of life for the patient with metastatic breast cancer.
• While studies of CTCs testing of patients with early-stage breast cancer suggest their potential utility, additional studies are necessary to determine the utility of CTCs in early breast cancer.
The National Academy of Clinical Biochemistry (NACB): the NACB published Laboratory Medicine Practice Guidelines for Use of Tumor Markers in Testicular, Prostate, Colorectal, Breast, and Ovarian Cancers (NACB, 2009). The guideline includes the following recommendations:
• Regarding measurement of circulating prostate cancer cells in peripheral blood, it is noted, “While initial results are encouraging, these techniques are not yet sufficiently validated to warrant recommendations their application in routine clinical practice.”
• Regarding detection of tumor cells in circulation in breast cancer, it is noted that, this testing is undergoing evaluation; it is available but not widely used in clinical practice; and prospective randomized trial are underway.
In conclusion, CTC analysis is promising but not been proven as a clinically meaningful tool.
Hayes DF, Smerage J. (2008). “Is There a Role for Circulating Tumor Cells in the Management of Breast Cancer?”. Clin Cancer Res 14 (12): 3646–50.
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Pantel K, Riethdorf S. (2009). “Pathology: are circulating tumor cells predictive of overall survival?”. Nat Rev Clin Oncol. 6 (4): 190–1.
Panteleakou Z, Lembessis P, Sourla A, et al. (2009). “Detection of circulating tumor cells in prostate cancer patients: methodological pitfalls and clinical relevance”. Mol Med 15 (3-4): 101–14.
Harris L, Fritsche H, Mennel R, Norton L, Ravdin P, Taube S, et al. ; American Society of Clinical Oncology. American Society of Clinical Oncology 2007 update of recommendations for the use of tumor markers in breast cancer. J Clin Oncol. 2007 Nov 20;25(33):5287-312.
National Academy of Clinical Biochemistry (NACB). Laboratory Medicine Practice Guidelines for use of tumor markers in testicular, prostate, colorectal, breast, and ovarian cancers. Sturgeon CM, Diamandis EP editors. 2009. Accessed January 4, 2012. Available at URL address: http://www.aacc.org/members/nacb/LMPG/OnlineGuide/PublishedGuidelines/major