Circulating Tumor Cells Provide Information about Prognosis

The number of cancer tumor cells circulating in the bloodstream can provide information about prognosis and survival for people with metastatic colorectal cancer.  Measuring circulating tumor cells before beginning a treatment and then during treatment can help doctors decide if the therapy is working or whether cancer is getting worse.

Tumor cells can be found in the blood of cancer patients, but are very rare in healthy people.  Using a technique that identifies and magnetically separates circulating tumor cells, researchers were able to measure the number of circulating cells in a standard amount of blood. They measured circulating tumor cells before treatment began and again several times during treatment.

CT scans were used to measure cancer that wasn’t responding to treatment and was getting worse (progression.) The number of circulating tumor cells (CTCs) was then correlated to progression and then to overall survival.

Three or more cells in 7.5 ml of blood indicated a poor prognosis.

Circulating Tumor Cells to Forecast Prognosis

Before treatment began, about a quarter of patients (26 percent) had three or more CTC’s.  Their progression-free survival and overall survival was significantly poorer than those with fewer CTC’s.  Median progression-free survival was 4.5 months compared to 7.2 months.  Survival  was 9.4 months versus 15.5 months in patients with fewer circulating tumor cells.

Circulating Tumor Cells to Predict Successful Treatment

Blood was drawn and CTCs counted at successive points during treatment.  When the number of cells remained below 3, both progression-free and overall survival were significantly longer.  As the number of cells increased, survival time fell.

Favorable (less than 3) or unfavorable (3 or more) circulating tumor cells could be combined with information from imaging scans to predict median survival time.

• The best survival (18.8 months) occurred when their was no progressive disease found by the first scan after treatment began and CTC was favorable.
• Even in the presence of progressive disease on the initial scan, favorable CTC predicted longer survival (8.3 months).
• When there were unfavorable CTCs and no change on scans, survival was 7.1 months.
• The worst (3.1 months) was when cancer had progressed on the first scan and there were also unfavorable CTC counts.

The research team points out that a variety of chemo regimens were used in determining results in their study which was a drawback.  Survival times varied among regimens, but the trends found by measuring CTCs still were able to provide information about life expectancy for people with metastatic colorectal cancer.

Stephen Cohen M.D. and his colleagues in the United States and the Netherlands concluded,

The number of circulating tumor cells before and during treatment is an independent predictor of progression-free survival and overall survival in patients with metastatic colorectalcancer. CTCs provide prognostic information in addition to that of imaging studies.

SOURCE: Cohen et. al., Journal of Clinical Oncology, Volume 26, Number 19, July 1, 2008.

Watch a video produced by Veridex CellSearch about how circulating tumor cells are analyzed.