The significance of circulating tumor cells in prostate cancer patients undergoing adjuvant or salvage radiation therapy.

Following radical prostatectomy, success of adjuvant and salvage radiation therapy (RT) is dependent on the absence of micrometastatic disease. However, reliable prognostic/predictive factors for determining this are lacking.

Therefore, novel biomarkers are needed to assist with clinical decision-making in this setting Enumeration of circulating tumor cells (CTCs) using the regulatory-approved CellSearch System (CSS) is prognostic in metastatic prostate cancer We hypothesize that CTCs may also be prognostic in the post-prostatectomy setting

Patient blood samples (n=55) were processed on the CSS to enumerate CTCs at 0, 6, 12 and 24 months after completion of RT CTC values were correlated with predictive/prognostic factors and progression-free survival

CTC status (presence/absence) correlated significantly with positive margins (increased likelihood of CTC(neg) disease; P=0 032), and trended toward significance with the presence of seminal vesicle invasion (CTC(pos); P=0 113) and extracapsular extension (CTC(neg); P=0 116) Although there was a trend toward a decreased time to biochemical failure (BCF) in baseline CTC-positive patients (n=9), this trend was not significant (hazard ratio (HR)=0 3505; P=0 166) However, CTC-positive status at any point (n=16) predicted for time to BCF (HR=0 2868; P=0 0437)

One caveat of this study is the small sample size utilized (n=55) and the low number of patients with CTC-positive disease (n=16) However, our results suggest that CTCs may be indicative of disseminated disease and assessment of CTCs during RT may be helpful in clinical decision-making to determine, which patients may benefit from RT versus those who may benefit more from systemic treatments Prostate Cancer and Prostatic Disease advance online publication, 4 August 2015; doi:10 1038/pcan 2015 36

Prostate cancer and prostatic diseases 2015 Aug 04 [Epub ahead of print]

L E Lowes, M Lock, G Rodrigues, D D'Souza, G Bauman, B Ahmad, V Venkatesan, A L Allan, T Sexton

1] Department of Anatomy and Cell Biology, Schulich School of Medicine and Dentistry, Western University, London, Ontario, Canada [2] London Regional Cancer Program, London Health Sciences Centre, London, Ontario, Canada , 1] London Regional Cancer Program, London Health Sciences Centre, London, Ontario, Canada [2] Department of Oncology, Schulich School of Medicine and Dentistry, Western University, London, Ontario, Canada , 1] London Regional Cancer Program, London Health Sciences Centre, London, Ontario, Canada [2] Department of Oncology, Schulich School of Medicine and Dentistry, Western University, London, Ontario, Canada , 1] London Regional Cancer Program, London Health Sciences Centre, London, Ontario, Canada [2] Department of Oncology, Schulich School of Medicine and Dentistry, Western University, London, Ontario, Canada , 1] London Regional Cancer Program, London Health Sciences Centre, London, Ontario, Canada [2] Department of Oncology, Schulich School of Medicine and Dentistry, Western University, London, Ontario, Canada , 1] London Regional Cancer Program, London Health Sciences Centre, London, Ontario, Canada [2] Department of Oncology, Schulich School of Medicine and Dentistry, Western University, London, Ontario, Canada , 1] London Regional Cancer Program, London Health Sciences Centre, London, Ontario, Canada [2] Department of Oncology, Schulich School of Medicine and Dentistry, Western University, London, Ontario, Canada , 1] Department of Anatomy and Cell Biology, Schulich School of Medicine and Dentistry, Western University, London, Ontario, Canada [2] London Regional Cancer Program, London Health Sciences Centre, London, Ontario, Canada [3] Department of Oncology, Schulich School of Medicine and Dentistry, Western University, London, Ontario, Canada , 1] London Regional Cancer Program, London Health Sciences Centre, London, Ontario, Canada [2] Department of Oncology, Schulich School of Medicine and Dentistry, Western University, London, Ontario, Canada [3] Medical Biophysics, Schulich School of Medicine and Dentistry, Western University, London, Ontario, Canada

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