CTC levels could provide a prostate cancer survival clue

New research supports the use of a circulating tumor cell (CTC) blood test, rather than the standard PSA biomarker diagnostic, to predict a patient's odds of surviving prostate cancer.

A team at the University of Southern California Norris Comprehensive Cancer Center (part of the Keck School of Medicine) produced the latest finding. Details were published in the Journal of Clinical Oncology on March 10. There are already plans to move ahead, to study whether choosing a cancer treatment based on changes in CTC counts can improve disease outcomes.

The study used blood samples from prostate cancer patients enrolled in a Phase III clinical trial involving docetaxel. According to USC, the team determined baseline counts of CTCs in blood samples before chemotherapy for 263 men. They took CTC measurements again three weeks after chemotherapy in order to gauge a patient's survival rate. They found that patients with much higher CTC levels after chemotherapy faced a risk of death at least 5 times higher. But patients saw their death risk slashed in half if their CTC levels plunged by 50% or greater.

The test reinforces the notion that CTC levels could serve as a biomarker to assess prostate cancer patients and which treatments might help them survive best. The researchers are plowing ahead, but they need more answers at the molecular level that could help personalize prostate cancer treatment even further. For example, finding out what genes the CTCs express as well as their mutations could enable more customized treatment, the researchers noted.

A CTC test could also be more precise than the standard of care: the prostate specific antigen, or PSA, test. PSA is a protein produced by cells of the prostate gland, and prostate cancer patients are often, but not always, found to have elevated PSA levels. But CTCs are rare in the body, often just 100 in a typical blood sample, and so they are a telling sign because cancer tumors shed them into blood.

Testing for CTCs for prostate and other cancers is gaining steam. Scientists at the University of California, Los Angeles, and Cedars-Sinai Medical Center, for example, developed something dubbed the NanoVelcro Chip that they believe can be used to track CTCs in the blood to monitor the evolution of prostate cancer in the body to provide the right treatment at the right time. Scientists at the University of Texas MD Anderson Cancer Center are also looking at creating a CTC blood test as a marker to predict the outcome of early stage breast cancer. San Diego's Epic Sciences recently inked a deal with global giant LabCorp ($LH) to provide access to its CTC testing technology to make it available to European drug developers focused on a variety of cancers.

- read the release
 here's the journal abstract

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