Changes in circulating tumor cell levels may predict treatment outcomes in castration-resistant prostate cancer more accurately than changes in prostate-specific antigen (PSA) levels, according to a study presented at the 13th Central European Meeting of the European Association of Urology in Prague, the Czech Republic.

Circulating tumor cell levels have prognostic significance in patients with breast and colorectal cancer, and may also be important in prostate cancer. However, circulating tumor cell levels are not being used to guide treatment decisions on a routine basis.

“The research of the circulating tumor cells is of utmost importance, because nowadays there is no reliable marker of both cancer-specific or overall survival in castration-resistant prostate cancer patients,” said Otakar Čapoun, MUDr, Department of Urology at General Teaching Hospital Charles University in Prague, Czech Republic and lead author of the study.

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Čapoun said that the goal is to individualize management of prostate cancer that is castration-resistant. If men do not respond to chemotherapy with a decrease in circulating tumor cell levels early in the course of treatment, then another therapy may need to be considered.

In this study, peripheral blood was collected from 17 men with metastatic castration-resistant prostate cancer prior to docetaxel therapy and after the fourth cycle of chemotherapy. Circulating tumor cells were detected using immunomagnetic separation, and multiplex-PCR was performed after cytolysis of the cells to quantify tumor-associated antigens (prostate specific antigen, prostate specific membrane antigen, and epidermal growth factor receptor).

A favorable change in circulating tumor cell levels occurred in more than half of the men during chemotherapy. However, the change in circulating tumor cell levels did not correlate with changes in the serum prostate specific antigen level.

“This research project is divided into several arms, among others, we are investigating the feasibility of circulating tumor cell cultivation and genetic profiling,” Čapoun said. “This gene profile will be compared with primary tumor at the time of diagnosis. In the future, this circulating tumor cell profiling might be useful for even more accurate and better tailored selection of treatment for castration-resistant prostate cancer.”