Circulating tumour cells in prostate cancer patients receiving salvage radiotherapy

ABSTRACT

INTRODUCTION: Within 10 years of radical prostatectomy (RP), up to 30% of prostate cancer (PCa) patients will have a rise in prostate-specific antigen (PSA), requiring radiation therapy (RT). However, with current technology, distinction between local and distant recurrent PCa is not possible. This lack of an accurate test constrains the decision whether to offer systemic or local treatment. We hypothesise tests for detecting circulating tumour cells (CTCs) within the blood may assist with clinical decision-making and in this pilot study we investigated whether CTCs could be detected in this patient population using the CellSearch® system. MATERIALS AND METHODS: Blood samples were collected from PCa patients (n=26) prior to RT and 3 months following completion of RT. Samples were analysed for PSA level via immunoassay and CTC number using the CellSearch® system. RESULTS: CTCs could be detected in this patient population and following RT CTCs appeared to decrease. However, no association was observed between a higher PSA and an increased number of CTCs pre- or post-RT. Interestingly, patients who failed RT trended toward an increased/ unchanged number of CTCs following RT vs. a decreased number in patients with RT response. CONCLUSIONS: Our results demonstrate that CTCs can be detected in early-stage PCa and suggest the possibility that post-treatment reduction in CTC levels may be indicative of RT response . We are currently evaluating CTCs in a larger cohort of patients to validate our preliminary findings and further investigate the prognostic value of CTCs in this patient population (AU)