Nevada Cancer Institute publishes paper on validity of CellSearch

and LDH blood tests

A group of Nevada Cancer Institute physicians and scientists have demonstrated in a recent published study that among 11 blood tests, the CellSearch Circulating Tumor Cell (CTC) assay and the LDH test provide the most prognostic information for prostate cancer patients starting a new line of therapy, particularly as it relates to survival.

The study, titled “Circulating Tumor Cells in Patients with Castration-Resistant Prostate Cancer Baseline Values and Correlation with Prognostic Factors” was published in the June 2009 issue of Cancer Epidemiology, Biomarkers and Prevention, a journal that focuses on cutting-edge biomarkers with the high likelihood of shaping future diagnosis, prognosis and therapeutic decision-making.

The paper details the use of the CellSearch CTC assay in 100 patients with prostate cancer who are no longer responsive to hormonal therapy.  It represented one of the largest single institution experiences with this test.

 “This simple blood test helps guide therapeutic decision making, helping us to identify patients at higher risk from prostate cancer death,” said Dr. Oscar B. Goodman, assistant member, Department of Clinical Oncology.  “It also predicts which patients are at risk of having cancer that has spread and can be picked up by scans.”  

All nine of the physicians and scientists performing this study worked at NVCI during the research stage; they were Oscar B. Goodman, Louis M. Fink, James T. Symanowski, Bryan Wong, Beth Grobaski, David Pomerantz, Yupo Ma, David C. Ward and Nicholas J. Vogelzang.

In early 2008, CTC counting was approved by the FDA for monitoring patients with prostate cancer that has spread outside the prostate gland and no longer responds to initial hormonal manipulation that depletes androgens (male sex hormones, widely held to initially promote the growth of cancer cells).  Much like leukemia, cancer cells circulate in the bloodstream in the majority of these patients and can therefore be detected by a simple blood test.  

After obtaining CTC counts together with 11 other blood tests and an in-depth clinical history, these 100 patients began a new line of therapy that was monitored for up to 26 months with regard to survival.  This study answered a number of questions regarding this test, including its proper usage and how it compared to other conventional blood tests such as the standard PSA with respect to its ability to predict who is at risk of succumbing to prostate cancer.  

In the study, survival for patients with favorable CTC counts (low levels of CTC, less than 4 cells) could not be estimated due to the low number of deaths, while patients with unfavorable counts (high levels of CTC, 4 or more cells) survived a median period (50% percentile) of a little over 8 months. 

 “The results of this study will have far-reaching effects on how we test for prostate cancer and which patients we treat aggressively,” said Dr. Goodman.

From the blood tests performed, only CTC and LDH had independent value at prognosticating outcomes (PSA, the most commonly used biomarker, did not).  Also, in patients without detectable spread of disease on CAT or bone scans, CTC counts were always low, raising the possibility that in select patients this test may be used in lieu of scans.

The abstract can be found HERE.