title: Individual variations of serum testosterone in patients with prostate cancer receiving androgen deprivation therapy.
abstract: OBJECTIVE
  To analyse individual variations in serum testosterone level, the cumulative rate of 'breakthrough' increases over castrate levels, and to evaluate whether the increases can be predicted.
  
  
  METHODS
  Serum testosterone levels were determined every 6 months over 3 years in 73 consecutive patients with prostate cancer who were medically castrated, prospectively enrolled in a single tertiary academic centre. Patients recruited for this study were being treated with a 3-monthly depot of luteinizing hormone-releasing hormone agonist over 6-48 months. Serum testosterone was measured using a chemiluminescent assay with a lower sensitivity level of 15 ng/dL and interassay coefficient of variation of 25% at low testosterone concentrations.
  
  
  RESULTS
  Individual variations could not be explained by the interassay variation coefficient in 26% of the patients. The rate of breakthrough increases >50 ng/dL increased from 12.3% at the first determination to 24.7% at the third, then remaining stable. The rate of breakthrough increases of 20-50 ng/dL increased from 27.4% at the first determination to 31.5% at the second, and then remained stable. A first determination of <20 ng/dL provided an 11.4% probability for future increases of >50 ng/dL, with a 5.7% probability if two consecutive determinations were <20 ng/dL and a null probability when three consecutive determinations were <20 ng/dL.
  
  
  CONCLUSIONS
  Individual variations in serum testosterone level cannot be explained by the coefficient of variation of the assay in a quarter of patients who are medically castrated. Breakthrough increases over castrate levels increase over time and those of >50 ng/dL can be predicted from the previous levels.
authors.affiliation: Department of Urology, Vall d'Hebron Hospital, Autónoma University of Barcelona, Barcelona, Spain. jmorote@vhebron.net
authors.forename: Juan
authors.initials: J
authors.lastname: Morote
authors.forename: Jacques
authors.initials: J
authors.lastname: Planas
authors.forename: Carlos
authors.initials: C
authors.lastname: Salvador
authors.forename: Carles X
authors.initials: CX
authors.lastname: Raventós
authors.forename: Roberto
authors.initials: R
authors.lastname: Catalán
authors.forename: Jaume
authors.initials: J
authors.lastname: Reventós
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000726:Androgen Antagonists / Q000627:therapeutic use*; D000813:Anilides / Q000627:therapeutic use*; D007987:Gonadotropin-Releasing Hormone / Q000819:agonists*; D006801:Humans; D008163:Luminescent Measurements; D008297:Male; D008875:Middle Aged; D009570:Nitriles / Q000627:therapeutic use*; D011446:Prospective Studies; D011471:Prostatic Neoplasms / Q000097:blood / Q000188:drug therapy*; D012680:Sensitivity and Specificity; D013739:Testosterone / Q000097:blood*; D014105:Tosyl Compounds / Q000627:therapeutic use*
chemical_list: D000726:Androgen Antagonists; D000813:Anilides; D009570:Nitriles; D014105:Tosyl Compounds; D007987:Gonadotropin-Releasing Hormone; D013739:Testosterone; C053541:bicalutamide