title: The significance of circulating tumor cells in prostate cancer patients undergoing adjuvant or salvage radiation therapy.
abstract: BACKGROUND
  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.
  
  
  METHODS
  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.
  
  
  RESULTS
  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).
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Anatomy and Cell Biology, Schulich School of Medicine and Dentistry, Western University, London, Ontario, Canada.|London Regional Cancer Program, London Health Sciences Centre, London, Ontario, Canada.
authors.forename: L E
authors.initials: LE
authors.lastname: Lowes
authors.affiliation: London Regional Cancer Program, London Health Sciences Centre, London, Ontario, Canada.|Department of Oncology, Schulich School of Medicine and Dentistry, Western University, London, Ontario, Canada.
authors.forename: M
authors.initials: M
authors.lastname: Lock
authors.affiliation: London Regional Cancer Program, London Health Sciences Centre, London, Ontario, Canada.|Department of Oncology, Schulich School of Medicine and Dentistry, Western University, London, Ontario, Canada.
authors.forename: G
authors.initials: G
authors.lastname: Rodrigues
authors.affiliation: London Regional Cancer Program, London Health Sciences Centre, London, Ontario, Canada.|Department of Oncology, Schulich School of Medicine and Dentistry, Western University, London, Ontario, Canada.
authors.forename: D
authors.initials: D
authors.lastname: D'Souza
authors.affiliation: London Regional Cancer Program, London Health Sciences Centre, London, Ontario, Canada.|Department of Oncology, Schulich School of Medicine and Dentistry, Western University, London, Ontario, Canada.
authors.forename: G
authors.initials: G
authors.lastname: Bauman
authors.affiliation: London Regional Cancer Program, London Health Sciences Centre, London, Ontario, Canada.|Department of Oncology, Schulich School of Medicine and Dentistry, Western University, London, Ontario, Canada.
authors.forename: B
authors.initials: B
authors.lastname: Ahmad
authors.affiliation: London Regional Cancer Program, London Health Sciences Centre, London, Ontario, Canada.|Department of Oncology, Schulich School of Medicine and Dentistry, Western University, London, Ontario, Canada.
authors.forename: V
authors.initials: V
authors.lastname: Venkatesan
authors.affiliation: Department of Anatomy and Cell Biology, Schulich School of Medicine and Dentistry, Western University, London, Ontario, Canada.|London Regional Cancer Program, London Health Sciences Centre, London, Ontario, Canada.|Department of Oncology, Schulich School of Medicine and Dentistry, Western University, London, Ontario, Canada.
authors.forename: A L
authors.initials: AL
authors.lastname: Allan
authors.affiliation: London Regional Cancer Program, London Health Sciences Centre, London, Ontario, Canada.|Department of Oncology, Schulich School of Medicine and Dentistry, Western University, London, Ontario, Canada.|Medical Biophysics, Schulich School of Medicine and Dentistry, Western University, London, Ontario, Canada.
authors.forename: T
authors.initials: T
authors.lastname: Sexton
mesh_terms: D014408:Biomarkers, Tumor; D002452:Cell Count; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D060787:Neoplasm Grading; D009367:Neoplasm Staging; D009360:Neoplastic Cells, Circulating / Q000473:pathology*; D017430:Prostate-Specific Antigen / Q000097:blood; D011471:Prostatic Neoplasms / Q000401:mortality / Q000473:pathology* / Q000532:radiotherapy*; D018714:Radiotherapy, Adjuvant; D016879:Salvage Therapy; D016019:Survival Analysis; D016896:Treatment Outcome
chemical_list: D014408:Biomarkers, Tumor; D017430:Prostate-Specific Antigen