title: Inadequacy of prostate-specific antigen doubling time estimates calculated using an ultrasensitive assay of prostate-specific antigen for biochemical failure after radical prostatectomy.
abstract: BACKGROUND
  The objective of this study was to evaluate the adequacy in calculating prostate-specific antigen doubling time (PSADT) using an ultrasensitive assay of prostate-specific antigen (PSA) for biochemical failure after radical prostatectomy (RP).
  
  
  METHODS
  In this research, we included 52 consecutive patients who experienced more than or equal to three consecutive increases in ultrasensitive PSA values after RP at two institutions. PSADT is to be calculated by fitting a linear model to post-nadir longitudinal logarithm ultrasensitive PSA (lnPSA) values. The goodness of fit of linear model for longitudinal lnPSA values was evaluated by applying a mixed effect model for all patients or two groups divided by median PSADT.
  
  
  RESULTS
  Median PSADT was 4.7 months. A mixed effect model showed that the fit of linear model for longitudinal lnPSA values was not good in lower ultrasensitive PSA values for all patients (p < 0.0001) or the group with a value longer than the median PSADT (p < 0.0001), while it was not worse for the group with a value shorter than the median PSADT (p = 0.079).
  
  
  CONCLUSIONS
  These findings suggest that calculating PSADT using an ultrasensitive assay for biochemical failure after RP may still be open for discussion.
authors.affiliation: Department of Urology, Juntendo University, Tokyo, Japan. fshimizu-jua@umin.ac.jp
authors.forename: Fumitaka
authors.initials: F
authors.lastname: Shimizu
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Matsuyama
authors.forename: Takashi
authors.initials: T
authors.lastname: Tominaga
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Ohashi
authors.forename: Makoto
authors.initials: M
authors.lastname: Fujime
mesh_terms: D000368:Aged; D000704:Analysis of Variance; D001681:Biological Assay / Q000379:methods*; D014408:Biomarkers, Tumor / Q000032:analysis / Q000097:blood; D001707:Biopsy, Needle; D006801:Humans; D008297:Male; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local / Q000473:pathology; D009367:Neoplasm Staging; D011237:Predictive Value of Tests; D011336:Probability; D017430:Prostate-Specific Antigen / Q000032:analysis / Q000097:blood*; D011468:Prostatectomy; D011471:Prostatic Neoplasms / Q000097:blood* / Q000401:mortality / Q000473:pathology / Q000601:surgery*; D012189:Retrospective Studies; D018570:Risk Assessment; D012680:Sensitivity and Specificity; D015996:Survival Rate; D013997:Time Factors
chemical_list: D014408:Biomarkers, Tumor; D017430:Prostate-Specific Antigen