It is an exciting prospect, because metastasis and not primary tumors frequently represent the most serious threat to patients’ lives.

In the future, CTCs could become a central component of personalized cancer treatments, allowing not just the liquid biopsying of cancers that are inaccessible for tumor biopsy, but even laboratory assessments of which specific treatment regimens will be most effective against primary or metastatic tumors.17,18

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Caution should be taken, however; CTCs’ gene expression profiles are similar—but not identical—to their parent tumors.16 Moreover, it is not yet clear that switching chemotherapy regimens based on CTC values can really improve patient survival times. A phase 3 clinical trial presented at the 2013 San Antonio Breast Cancer Symposium reported that switching patients with elevated CTC counts did not improve patients’ OS or time to progression with metastatic breast cancer, for example (P>0.6; not significant).

But even if that disappointing result proves to be the norm in subsequent studies, CTCs appear poised to spare some patients unnecessary treatment morbidities.


  1. Harouaka R, Kang Z, Zheng SY, et al. Circulating tumor cells: advances in isolation and analysis, and challenges for clinical applications. Pharmacol Ther. 2014;141(2):209-221.
  2. Alix-Panabières C, Pantel K. Circulating tumor cells: liquid biopsy of cancer. Clin Chem. 2013;59(1):110-118.
  3. Krebs MG, Metcalf RL, Carter L, et al. Molecular analysis of circulating tumour cells—biology and biomarkers. Nat Rev Clin Oncol. 2014;11(3):129-144.
  4. Kim K, Lee KH, Lee J, Choi J. Overview of current standpoints in profiling of circulating tumor cells. Arch  Pharmol Res. 2014;37(1):88-95.
  5. Torino F, Bonmassar E, Bonmassar L, et al. Circulating tumor cells in colorectal cancer patients. Cancer Treat Rev. 2013;39(7):759-772.
  6. Raimondi C, Gradilone A, Naso G, et al. Clinical utility of circulating tumor cell counting through CellSearch®: the dilemma of a concept suspended in limbo. OncoTargets Ther. 2014;7:619-625.
  7. Becker TM, Caixeiro MJ, Lim SH, et al. New frontiers in circulating tumor cell analysis: a reference guide for biomolecular profiling toward translational clinical use. Int J Cancer. 2014;134(11):2523-2533.
  8. Friedlander TW, Premasekharan G, Paris PL. Looking back to the future of circulating tumor cells. Pharmacol Ther. 2014;142(3):271-280.
  9. Rhim AD, Thege FI, Santana SM, et al. Detection of circulating pancreas epithelial cells in patients with pancreatic cystic lesions. Gastroenterol. 2014;146(3):647-651.
  10. Cristofanilli M. Circulating tumour cells: telling the truth about metastasis. Lancet Oncol. 2014;15(4):365-366.
  11. Bidard FC, Peeters DJ, Fehm T, et al. Clinical validity of circulating tumour cells in patients with metastatic breast cancer: a pooled analysis of individual patient data. Lancet Oncol. 2014;15(4):406-414.
  12. Alix-Panabières C, Pantel K. Technologies for detection of circulating tumor cells: facts and vision. Lab Chip. 2014;14(1):57-62.
  13. Alunni-Fabbroni M, Muller V, Fehm T, Janni W, Rack B. Monitoring in metastatic breast cancer: is imaging outdated in the era of circulating tumor cells? Breast Care (Basel). 2014;9(1):16-21.
  14. Dawson SJ, Tsui DWY, Murtaza M, et al. Analysis of circulating tumor DNA to monitor metastatic breast cancer. N Engl J Med. 2013;368(13):1199-1209.
  15. Scatena R, Bottoni P, Giardina B. Circulating tumor cells and cancer stem cells: a role for proteomics in defining the interrelationships between function, phenotype and differentiation with potential clinical applications. Biochim Biophys Acta. 2013;1835(2):129-143.
  16. Steinert G, Schölch S, Niemietz T, et al. Immune escape and survival mechanisms in circulating tumor cells of colorectal cancer. Cancer Res. 2014;74(6):1694-1704.
  17. Hughes AD, Marshall JR, Keller E, et al. Differential drug responses of circulating tumor cells within patient blood. Cancer Lett. 2013 Aug 21. DOI: 10.1016/j.canlet.2013.08.026. [Epub ahead of print]
  18. Onstenk W, Gratam JW, Foekens JA, et al. Toward a personalized breast cancer treatment approach guided by circulating tumor cell (CTC) characteristics. Cancer Treat Rev. 2013;39(7):691-700.