Circulating Tumor Cells (CTC) are tumor cells which are released by primary tumor into the bloodstream. Recent research over the years has shown that CTC plays a vital role in cancer metastasis, which means that CTC is responsible for the spread of cancer from the primary tumor to other organs. CTC are rarely found in healthy people or in people with nonmalignant tumors. A scientific study conducted by Allard et al. (2004)1, reported that only 1 out of 344 (0.3%) healthy individuals and those with non-malignant disease had >1 CTC detected in their blood, when they underwent the CELLSEARCH® Circulating Tumor Cell Test.
The monitoring of a cancer patient’s response to treatment is essential. While imaging techniques and protein markers may reflect cancer progression, these conventional methods have their limitations— Imaging techniques reflect the endpoint of cancer spread, but do not reveal the process of cancer progression, which may indicate treatment resistance.
A landmark study published in JAMA Oncology 2018, Sparano et al.2, reported that CTC counting reveals the risks of cancer recurrences in women 5 years after diagnosis of hormone receptor–positive breast cancer.