medwireNews: Study results add further support to the use of circulating tumor cells (CTCs) as an effective prognostic marker in prostate cancer, and suggest that they could be used to monitor metastatic disease progression.
Baseline CTC count had significant ability to discriminate between poor and good survival, was greatest in patients with bone metastases, and also correlated significantly with Gleason scores. However, in contrast to some previous findings, it only had a weak relationship with prostate-specific androgen (PSA) levels.
"Collectively, these data reinforce the idea that the PSA level alone is not of sufficient prognostic value and must be considered in conjunction with additional biomarkers," say Robert Amato (University of Texas, Houston, USA) and colleagues.
The study included 202 patients with prostate cancer, of whom 164 (81%) had received previous localized treatment for prostate cancer. Overall, 40 (20%) patients had bone-only metastases, 15 (7%) had lymph node-only metastases, and 24 (12%) had bone and lymph node metastases.
Among patients with CTC counts over 100/7.5 mL blood (n=7), the median overall survival was 70.7 months, while survival among patients with 5-100 CTCs/7.5 mL (n=21), and fewer than five CTCs/7.5 mL (n=18) was significantly greater at a median 73.3 and 78.5 months, respectively. Among patients with undetectable CTC counts (n=46), the median overall survival was not reached during follow up.
Additionally, the authors found that patients with bone-only metastases or bone and lymph node metastases had greater CTC numbers than those with lymph node-only metastases (mean 41.1 and 57.0 vs 2.5 cells/7.5 mL).
They also report that androgen-depleted patients had a greater mean CTC count than nonandrogen-depleted patients (26.4 vs 2.7 cells/7.5 mL), and there was a significant correlation between Gleason scores and CTC count. Meanwhile, there was only a weak, positive correlation between CTC counts and PSA level.
Amato and colleagues, writing in Urology, say that their results indicate that increased CTC burden is associated with disease progression and metastatic spread. Therefore, CTCs could provide a valuable means to tailor therapy according to progression.
"Measuring CTC levels, the 'liquid biopsy,' has the potential to be an informative biomarker in monitoring metastatic disease progression," they conclude.
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