Researchers have, for nearly the past 30 years, evaluated circulating tumor cells (CTCs) as a biomarker for cancer progression, particularly in prostate cancer.1 This measurement estimates the number of free-flowing cancer cells in a patient’s bloodstream based on blood draws taken at multiple time points, and can help predict, based on the number of these cells, the degree at which the disease may be advancing.

Yet the metric has come under significant scrutiny since the early investigations into its utility in the 1990s. The test’s reliability as a prognostic tool is still under development, as is the issue of which assays/platforms are best for determining CTC counts.2 It’s unknown, for example, whether CTC counts in patients with early or localized disease are as useful a metric as these counts are in the metastatic setting.2

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A recent paper published in JCO Precision Oncology, however, noted that 1 platform in particular — the Epic Sciences platform — may be able to identify which cases of untreated, high-risk prostate cancer are likely to recur after radiotherapy or radical prostatectomy.3

“The Epic platform is quite unique and likely one of the most sensitive platforms for identifying CTCs,” said Todd Morgan, MD, associate professor of urology at the University of Michigan in Ann Arbor, and final author of the study, in an email to Cancer Therapy Advisor. “It evaluates whole blood without a specific enrichment step, and then relies on staining, morphology, and subsequent digital algorithms to identify CTCs.”

Using the platform, the researchers evaluated blood samples collected (at a median follow-up of 14.2 months) from 45 patients with localized, high-risk disease prior to and during treatment. The investigators grouped the patients according to the type of treatment received: either radiotherapy plus androgen deprivation or radical prostatectomy with curative intent.

Samples from evaluable patients showed a diversity of CTC subtypes, including androgen receptor (AR)-positive, cytokeratin (CK)-positive, and CK-negative cells. Patients who underwent radical prostatectomy (15 of 26) were much more likely to have biochemical recurrence than were patients who received radiotherapy (1 of 19). The researchers also noted more metastatic events in the prostatectomy group (5 of 26) than in the radiotherapy group (1 in 19).