title: Circulating tumor cells in patients with castration-resistant prostate cancer baseline values and correlation with prognostic factors.
abstract: OBJECTIVE
  Circulating tumor cells (CTC) have been recently accepted by the Food and Drug Administration of the United States as a prognostic tool in advanced prostate cancer. However, a number of questions remain about the use of the test. The optimal clinical cut-off has never been determined. Also, the predictive value of CTCs in the setting of low-burden advanced prostate cancer has not been evaluated. Herein we describe our experience with the CellSearch method of CTC enumeration.
  
  
  METHODS
  CTCs enumerated from 100 patients with castration-resistant prostate cancer were correlated with clinicopathologic characteristics and conventional biomarkers, such as prostate-specific antigen and lactate dehydrogenase. Patients received ongoing medical oncologic follow-up for up to 26 months, and overall survival status was documented.
  
  
  RESULTS
  Forty-nine of the patients (49%) were alive at the end of the study. CTC counts correlate well with overall survival (P < 0.001) but are also tightly interrelated to other biomarkers. Threshold analysis identified 4 CTC/7.5 cc (compared with the approved value of 5) as an optimal cut-off value with respect to correlation with survival outcomes as well as predictive of metastatic disease. Univariate analysis confirmed a tight interrelationship between cut-off CTC values and biomarkers. Multivariate analysis with bootstrap sampling validation identified lactate dehydrogenase (P = 0.002) and CTCs (P = 0.001) as independently prognostically significant.
  
  
  CONCLUSIONS
  Baseline CTC values provide important prognostic information and specific prediction of metastatic disease. Their presence correlates with classic biomarkers.
authors.affiliation: Department of Clinical Oncology, Nevada Cancer Institute, One Breakthrough Way, Las Vegas, Nevada 89135, USA.
authors.forename: Oscar B
authors.initials: OB
authors.lastname: Goodman
authors.forename: Louis M
authors.initials: LM
authors.lastname: Fink
authors.forename: James T
authors.initials: JT
authors.lastname: Symanowski
authors.forename: Bryan
authors.initials: B
authors.lastname: Wong
authors.forename: Beth
authors.initials: B
authors.lastname: Grobaski
authors.forename: David
authors.initials: D
authors.lastname: Pomerantz
authors.forename: Yupo
authors.initials: Y
authors.lastname: Ma
authors.forename: David C
authors.initials: DC
authors.lastname: Ward
authors.forename: Nicholas J
authors.initials: NJ
authors.lastname: Vogelzang
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D018931:Antineoplastic Agents, Hormonal; D014408:Biomarkers, Tumor / Q000032:analysis*; D019008:Drug Resistance, Neoplasm; D006801:Humans; D053208:Kaplan-Meier Estimate; D008297:Male; D008875:Middle Aged; D009360:Neoplastic Cells, Circulating / Q000473:pathology*; D011379:Prognosis; D011471:Prostatic Neoplasms / Q000097:blood* / Q000401:mortality* / Q000473:pathology*
chemical_list: D018931:Antineoplastic Agents, Hormonal; D014408:Biomarkers, Tumor