title: Prognostic significance of time to prostate-specific antigen (PSA) nadir and its relationship to survival beyond time to PSA nadir for prostate cancer patients with bone metastases after primary androgen deprivation therapy.
abstract: BACKGROUND
  This study investigated the prognostic significance of time to the prostate-specific antigen nadir (TTPN) and its relationship to survival beyond TTPN in metastatic prostate cancer after primary androgen-deprivation therapy (ADT).
  
  
  METHODS
  All metastatic prostate cancer patients treated with primary ADT from 2000 to 2009 were reviewed. The prognostic significance of TTPN in predicting progression-free survival (PFS) beyond TTPN and overall survival (OS) beyond TTPN was analyzed using the Cox regression model. The median PFS and OS were plotted against TTPN on a monthly interval. The PFS beyond TTPN and the OS beyond TTPN with reference to TTPN were calculated and presented.
  
  
  RESULTS
  The study enrolled 419 patients with a median follow-up period of 38 months. The findings showed that TTPN was a significant prognostic indicator for both PFS beyond TTPN (hazard ratio [HR] 0.72, 95 % confidence interval [CI] 0.52-0.99, p = 0.04) and OS beyond TTPN (HR 0.65, 95 % CI 0.47-0.90, p = 0.01) according to Cox regression analyses. The relationship between TTPN and survival beyond TTPN consisted of three phases. In the first phase (<3 months for PFS and <6 months for OS), the survival beyond TTPN increased with TTPN. In the second phase (3-17 months for PFS and 6-20 months for OS), the survival beyond TTPN remained relatively static. In the third phase (>17 months for PFS and >20 months for OS), the survival beyond TTPN increased exponentially with TTPN.
  
  
  CONCLUSIONS
  In this study, TTPN was a good prognostic indicator for PFS beyond TTPN and OS beyond TTPN in metastatic prostate cancer cases after primary ADT. Different TTPNs had different implications for predicting survival beyond TTPN.
authors.affiliation: Division of Urology, Department of Surgery, The Chinese University of Hong Kong, Prince of Wales Hospital, Shatin, Hong Kong, China.
authors.forename: Jeremy Yuen Chun
authors.initials: JY
authors.lastname: Teoh
authors.forename: James Hok Leung
authors.initials: JH
authors.lastname: Tsu
authors.forename: Steffi Kar Kei
authors.initials: SK
authors.lastname: Yuen
authors.forename: Samson Yun Sang
authors.initials: SY
authors.lastname: Chan
authors.forename: Peter Ka Fung
authors.initials: PK
authors.lastname: Chiu
authors.forename: Wai-Man
authors.initials: WM
authors.lastname: Lee
authors.forename: Ka-Wing
authors.initials: KW
authors.lastname: Wong
authors.forename: Kwan-Lun
authors.initials: KL
authors.lastname: Ho
authors.forename: Simon See Ming
authors.initials: SS
authors.lastname: Hou
authors.forename: Chi-Fai
authors.initials: CF
authors.lastname: Ng
authors.forename: Ming-Kwong
authors.initials: MK
authors.lastname: Yiu
mesh_terms: D000368:Aged; D000726:Androgen Antagonists / Q000627:therapeutic use*; D001859:Bone Neoplasms / Q000097:blood / Q000188:drug therapy / Q000401:mortality* / Q000556:secondary; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D060787:Neoplasm Grading; D009367:Neoplasm Staging; D009376:Neoplasms, Hormone-Dependent / Q000097:blood / Q000188:drug therapy / Q000401:mortality* / Q000473:pathology; D011379:Prognosis; D017430:Prostate-Specific Antigen / Q000097:blood*; D011471:Prostatic Neoplasms / Q000097:blood / Q000188:drug therapy / Q000401:mortality* / Q000473:pathology; D018570:Risk Assessment; D015996:Survival Rate; D013997:Time Factors
chemical_list: D000726:Androgen Antagonists; D017430:Prostate-Specific Antigen