title: Role of ultrasensitive prostate-specific antigen in the follow-up of prostate cancer after radical prostatectomy.
abstract: OBJECTIVE
  Prostate-specific antigen (PSA) is an important tool in the follow-up of prostate cancer after radical prostatectomy (RP). However, the relevance of ultrasensitive PSA (uPSA) after RP is not well defined. The aim of this study was to investigate the value of uPSA in follow-up after RP and to determine whether ultrasensitive PSA doubling time (uDT) correlates with traditional PSA doubling time (tDT).
  
  
  METHODS
  In total, 604 consecutive patients undergoing open RP and pelvic lymphadenectomy between 2004 and 2008 (minimum 5y of follow-up) were studied. To evaluate the postsurgical uPSA level, scatter plot statistics were used. To correlate uDT and tDT in patients with a biochemical recurrence (PSA ≥0.2ng/ml), at least 2 uPSA and 2 PSA measurements without salvage treatment were required and a weighted Cohen kappa statistic and receiver operating characteristic curve were used to test agreement across the categories.
  
  
  RESULTS
  There were 229 patients without biochemical recurrence who did not have 3 rising PSA values after nadir within ultrasensitive area. Their highest uPSA value was between 0.003 and 0.1ng/ml. In 97.4% of patients, the highest uPSA value was less than 0.03ng/ml, and in 89% of these patients, the values were less than 0.02ng/ml. The median uDT and tDT were 10.2 and 11.4 months, respectively. The weighted Cohen kappa statistic between these 2 groups was 0.30 (95% CI:-0.09 to 0.50), demonstrating a poor agreement of PSA doubling time across categories. The predictive capability of uDT was tested with tDT <9 months. A receiver operating characteristic curve area under the curve value was 0.737 (95% CI:-0.577 to 0.897) demonstrating a fair agreement between the groups.
  
  
  CONCLUSIONS
  uPSA values>0.03ng/ml seems to be valid and can be used in a clinical setting. There was a poor to fair agreement between tDT and uDT. The accuracy of uDT improves when it approaches the traditional PSA threshold of 0.1ng/ml. Also according to our results, there is no prognostic benefit of uDT calculation.
authors.affiliation: Department of Urology, Turku University Hospital, Turku, Finland. Electronic address: heikki.seikkula@tyks.fi.
authors.forename: Heikki
authors.initials: H
authors.lastname: Seikkula
authors.affiliation: Department of Urology, Turku University Hospital, Turku, Finland.
authors.forename: Kari T
authors.initials: KT
authors.lastname: Syvänen
authors.affiliation: Auria Biobank, Turku University Hospital, Turku, Finland.
authors.forename: Samu
authors.initials: S
authors.lastname: Kurki
authors.affiliation: Department of Pathology (HUSLAB), Helsinki University Hospital, and Institute for Molecular Medicine Finland (FIMM), Helsinki, Finland.
authors.forename: Tuomas
authors.initials: T
authors.lastname: Mirtti
authors.affiliation: Department of Pathology, University of Turku and Turku University Hospital, Turku, Finland.
authors.forename: Pekka
authors.initials: P
authors.lastname: Taimen
authors.affiliation: Department of Urology, Turku University Hospital, Turku, Finland.
authors.forename: Matti
authors.initials: M
authors.lastname: Laato
authors.affiliation: Department of Urology, Turku University Hospital, Turku, Finland.
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Boström
keywords: PSA doubling time; Prostate cancer; Radical prostatectomy; Ultrasensitive PSA