title: Circulating tumor cells in patients with metastatic castration resistant prostate cancer: exploratory findings at a tertiary referral hospital.
abstract: OBJECTIVE
  In patients with metastatic castration-resistant prostate cancer (mCRPC), the finding of less than five circulating tumor cells (CTCs)/7.5 mL blood before start of cytotoxic treatment or shortly thereafter indicates prolonged survival. In this descriptive pilot study, we investigated whether this association depends on the sequence of the therapeutic attempts.
  
  
  METHODS
  CTCs were determined in 41 mCRPC patients before and 2-3 months after starting first-line treatment with docetaxel (group 1) or second-line treatment with either radium-223 (group 2) or placebo/best supportive care (group 3). A "favorable" CTC count was defined as <5 CTC/7.5 mL blood. The results were related to overall survival.
  
  
  RESULTS
  Pretreatment, six of ten men in group 1, three of 19 in group 2, and three of 12 patients in group 3 had a favorable CTC count, leading to a significant difference between first- and second-line therapy (P=0.04). Decrease of pretreatment elevated CTCs to a favorable CTC count was significantly more often observed in patients on first-line therapy (three of four patients) than on second-line treatment (two of 26 men) (P=0.03). A favorable CTC count before or shortly after treatment start was observed in nine of ten patients on first-line and in eight of 31 men on second-line therapy (P=0.01). A favorable CTC count pretreatment or 2-3 months after therapy start was associated with beneficial overall survival in the three groups combined and in each group analyzed separately.
  
  
  CONCLUSIONS
  In mCRPC, a favorable CTC count before or 2-3 months after start of therapy is associated with length of overall survival, though such favorable CTC counts are observed significantly less often in patients on second- than on first-line therapy.
authors.affiliation: National Resource Center for Late Effects after Cancer Treatment, Norwegian Radium Hospital, Oslo University Hospital, Radiumhospital, Oslo, Norway.
authors.forename: Sophie D
authors.initials: SD
authors.lastname: Fosså
authors.affiliation: National Resource Center for Late Effects after Cancer Treatment, Norwegian Radium Hospital, Oslo University Hospital, Radiumhospital, Oslo, Norway.
authors.forename: Siri L
authors.initials: SL
authors.lastname: Hess
authors.affiliation: Department of Medical Biochemistry, Norwegian Radium Hospital, Oslo University Hospital, Radiumhospital, Oslo, Norway.
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Paus
authors.affiliation: Department of Pathology, Norwegian Radium Hospital, Oslo University Hospital, Radiumhospital, Oslo, Norway.
authors.forename: Elin
authors.initials: E
authors.lastname: Borgen
keywords: first-line treatment; overall survival; second-line treatment