Quantification of disseminated tumor cells in the bloodstream of patients with hormone-refractory prostate carcinoma undergoing cytotoxic chemotherapy

Only very limited data are available on the presence of circulating tumor cells during cytotoxic chemotherapy for hormone-refractory prostate cancer. We analyzed 241 blood samples from 32 patients with hormone-refractory PCa under a chemotherapy schedule. The etoposide, estramustine phosphate and paclitaxel scheme as well as the mitoxantrone and prednisone schedule were used to treat patients with advanced prostate cancer. The pre-therapy serum PSA values were in the range from 1.4 ng/ml to 2,870.9 ng/ml (median 74.5 ng/ml). We isolated the CD45-negative cell population by immunomagnetic depletion from 16 ml of peripheral blood samples. These cells were stained for pan-cytokeratin and evaluated. Patients were observed for an average of 67 weeks (range 16-120). In 77 (32%) samples originating from 27 (84%) patients, tumor cells were detected at least once. Twenty of these patients had shown an initial response to therapy as indicated by a ≥50% decrease of the pre-therapy PSA value. Of these, 14 patients experienced a biochemical and/or a clinical progression. For 13 (93%) of them, circulating tumor cells were detectable during the time of PSA response, i.e. during the PSA decline and before a biochemical or clinical progression. However, we could not correlate the amount of circulating tumor cells with the observed PSA levels. This study demonstrates that circulating tumor cells are detectable during chemotherapy for hormone-refractory prostate cancer regardless of the degree of PSA response.