title: Unusually high prostate-specific antigen bounce after prostate brachytherapy: Searching for etiologic factors.
abstract: OBJECTIVE
  Determine whether fat distribution, body mass index, or clinical and dosimetric factors are associated with prostate specific antigen (PSA) bounce (PSAb) of ≥1.6 ng/mL in patients treated with permanent seed (125)I prostate brachytherapy (PB).
  
  
  METHODS
  We identified 23 patients with a PSAb of ≥1.6 ng/mL. For each patient with a bounce, at least one control with similar age (age ± 2 years, n=31) was identified. Control patients had to have no bounce (≤0.2 ng/mL) and a most recent PSA of <1 ng/mL. CT at Day 30 after PB was used to determine the volume of subcutaneous adipose tissue, visceral adipose tissue, and peri-prostatic fat. Univariate and multivariate logistic models were used to assess the association between PSAb and adipose tissue distribution and clinical and dosimetric factors.
  
  
  RESULTS
  Mean patient age was 62.3 ± 5.3 years. Mean PSAb height was 2.7 ± 0.8 ng/mL, and mean time to bounce was 9.6 ± 4 months. More than 90% of the patients reached a PSA nadir before PSAb within 12 months post-PB. Patients showing PSAb were more likely to have a T1c disease vs. T2a (odds ratio = 18.87; 95% confidence interval: 2.32-454.55; p=0.019) and a lower seed activity per cc of prostate volume (odds ratio=0.02; 95% confidence interval=0.42-2.22; p=0.026). Neither fat distribution nor body mass index was associated with PSAb (p=0.11-0.597).
  
  
  CONCLUSIONS
  Clinical and dosimetric factors play a role in PSAb of ≥1.6 ng/mL. Fat distribution is not associated with a PSAb. There is presently no satisfactory theory to explain the etiology of PSAb.
authors.affiliation: Departement of Radiation Oncology, Centre hospitalier de l'Université de Montréal (CHUM), Hôpital Notre-Dame Hospital, Montreal, Québec, Canada; CRCHUM-Centre de recherché du Centre Hospitalier de l'Université de Montréal, Montreal, Québec, Canada.
authors.forename: Ciprian
authors.initials: C
authors.lastname: Chira
authors.forename: Daniel
authors.initials: D
authors.lastname: Taussky
authors.forename: Nelson
authors.initials: N
authors.lastname: Gruszczynski
authors.forename: Aliza
authors.initials: A
authors.lastname: Meissner
authors.forename: Sandra
authors.initials: S
authors.lastname: Larrivée
authors.forename: Jean-Francois
authors.initials: JF
authors.lastname: Carrier
authors.forename: David
authors.initials: D
authors.lastname: Donath
authors.forename: Guila
authors.initials: G
authors.lastname: Delouya
mesh_terms: D000368:Aged; D014408:Biomarkers, Tumor / Q000097:blood; D015992:Body Mass Index; D001918:Brachytherapy / Q000379:methods*; D004307:Dose-Response Relationship, Radiation; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging; D017430:Prostate-Specific Antigen / Q000097:blood*; D011471:Prostatic Neoplasms / Q000097:blood / Q000175:diagnosis / Q000532:radiotherapy*; D011829:Radiation Dosage; D014057:Tomography, X-Ray Computed; D016896:Treatment Outcome
chemical_list: D014408:Biomarkers, Tumor; D017430:Prostate-Specific Antigen
keywords: PSA bounce; Permanent seed brachytherapy; Prostate cancer