Circulating tumor cell counts predict course of hard-to-treat prostate cancer

July 7, 2008

NEW YORK (Reuters Health) - In patients with castration-resistant prostate cancer, changes in the number of circulating tumor cells are a valuable means of monitoring response to chemotherapy and predicting survival, according to research presented Sunday in Lugano, Switzerland at a conference organized by the European Society for Medical Oncology.

"Assessment of treatment benefit represents a major challenge in castration-resistant prostate cancer," Dr. David Olmos from The Royal Marsden NHS Foundation Trust in the UK and colleagues note in a meeting abstract.

"Our study shows that circulating tumor cell counts can provide prognostic information about how patients are responding to therapy much earlier than other markers, such time-to-disease progression," Dr. Olmos noted in a telephone interview with Reuters Health.

Dr. Olmos and colleagues collected circulating tumor cells from 119 men with castration-resistant prostate cancer at baseline and after 1 and 2 cycles of chemotherapy.

In a Cox regression model, median overall survival was greater than 30 months in patients with less than 5 circulating tumor cells at baseline. A circulating tumor cell count greater than 5 at all time points was significantly associated with shorter overall survival.

Median overall survival for patients with circulating tumor cell counts greater than 50 at baseline was 6.3 months; it was 21.1 months for patients with circulating tumor cell counts greater than 5 but less than 50.

Change in circulating tumor cell counts at all evaluated post-treatment time points showed that increasing counts predicted worse outcome while decreasing counts predicted better outcome.

Moreover, prediction of overall survival based on circulating tumor cells was "in keeping with prediction based on time-to-progression," Dr. Olmos and colleagues report.

"We have observed that patients with declining numbers of circulating tumor cells can see a change in their initial prognosis, reflecting a potential benefit from therapy," Dr. Olmos said.

Based on these findings, the evaluation of circulating tumor cell counts as a surrogate of overall survival in large randomized studies is warranted, Dr. Olmos and colleagues conclude.