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.

References

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