Interpretive Handbook

Test 89162 :
Circulating Tumor Cells (CTC) for Colorectal Cancer by CellSearch, Blood

Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

According to the American Cancer Society, colorectal cancer claims approximately 50,000 lives each year, the vast majority of which are a result of metastatic disease. Although there are many options for the treatment of metastatic colorectal cancer, oncologists often have to wait several months before they can determine if a specific treatment is beneficial to the patient.


The CellSearch System identifies and enumerates the number of circulating tumor cells (CTCs) in a blood specimen.(1) Studies suggest that the number of CTCs is associated with progression-free and overall survival in patients with metastatic colorectal cancer.(2,3)

Useful For Suggests clinical disorders or settings where the test may be helpful

Aids in monitoring patients with metastatic colon cancer

Interpretation Provides information to assist in interpretation of the test results

Results are reported as favorable or unfavorable. In patients with metastatic colon cancer, the finding of > or =3 circulating tumor cells/7.5 mL of blood is predictive of shorter progression-free survival and overall survival.(2)

Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

This test is FDA approved only for monitoring colon cancer patients with metastatic disease and is not suitable for monitoring colon cancer patients with nonmetastatic disease.


The CellSearch System is FDA approved for breast and prostate cancer.

-For breast cancer patients, order CTCBC / Circulating Tumor Cells (CTC) for Breast Cancer by CellSearch, Blood.

-For prostate cancer patients, order CTCPC / Circulating Tumor Cells (CTC) for Prostate Cancer by CellSearch, Blood.


Patients on doxorubicin (Adriamvcin) must wait a minimum of 7 days after administration before blood can be drawn for this test.


Blood specimens must be drawn into a CellSave tube and be processed in the laboratory within 96 hours of draw.


This test does not provide information about the primary site of a tumor.


This test does not predict whether patients with unfavorable results will have better clinical outcomes if switched to alternative treatment regimens.


Interfering substances may cause the ferrofluid reagent to aggregate, which may compromise results. The analysis process may not be able to detect all CTCs in the sample.

Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

An interpretive report will be provided.

Clinical References Provides recommendations for further in-depth reading of a clinical nature

1. Allard WJ, Matera J, Miller MC, et al: Tumor cells circulate in the peripheral blood of all major carcinomas but not in healthy subjects or patients with nonmalignant diseases. Clin Cancer Res 2004 Oct;10:6897-6904

2. Cohen SJ, Punt CJ, Iannotti N, et al: Relationship of circulating tumor cells to tumor response, progression-free survival, and overall survival in patients with metastatic colorectal cancer. J Clin Oncol 2008 Jul;26(19):3213-3221

3. Cohen SJ, Punt CJ, Iannotti N, et al: Prognostic significance of circulating tumor cells in patients with metastatic colorectal cancer. Ann Oncol 2009;20(7):1223-1229