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Interpretive Handbook

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Test 60142:
Circulating Tumor Cells (CTC) for Prostate 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, prostate cancer claims approximately 28,000 lives each year, the vast majority of which are a result of metastatic disease. Although there are many options for the treatment of metastatic prostate cancer, oncologists often have to wait several months after initiation of treatment before they can determine if the 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 prostate cancer.(2,3)

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

An aid in the monitoring of patients with metastatic prostate cancer

Interpretation Provides information to assist in interpretation of the test results

In patients with metastatic prostate cancer, the finding of > or =5 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 prostate cancer patients with metastatic disease and is not suitable for monitoring prostate cancer patients with nonmetastatic disease.

 

The CellSearch System has also been FDA approved for breast and colon cancer. For breast cancer patients, order #89089 Circulating Tumor Cells (CTC) for Breast Cancer by CellSearch, Blood. For colon cancer patients, order #89162 Circulating Tumor Cells (CTC) for Colorectal 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 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 regiments.

 

The presence of ferrofluid aggregates observed after processing a patient specimen may lead to false negative results. A result from a specimen in which aggregation is observed and the CTC count is below 5 is invalid and the test is canceled per manufacturer's instructions. A retest is advised.

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. deBono JS, Scher HI, Montgomery RB, et al: Circulating tumor cells predict survival benefit from treatment in the metastatic castration-resistant prostate cancer. Clin Cancer Res 2008 October 1;14(19):6302-6309

3. Danila DC, Heller G, Gignac GA, et al: Circulating tumor cell number and prognosis in progressive castration-resistant prostate cancer. Clin Cancer Res 2007 December 1;13(23):7053-7058