title: Early and multiple PSA bounces can occur following high-dose prostate stereotactic body radiation therapy: Subset analysis of a phase 1/2 trial.
abstract: OBJECTIVE
  We hypothesized that high-dose stereotactic body radiation therapy (SBRT) would lead to faster time to nadir and lower nadir values compared with conventional radiation therapy experiences. We now report prostate-specific antigen (PSA) kinetics following high-dose SBRT in patients treated with radiation alone.
  
  
  METHODS
  Ninety-one patients were enrolled on the phase 1/2 dose escalation study of SBRT for localized prostate cancer. All patients with at least 36 months of follow-up and without hormone therapy were included in this analysis (n = 47). Treatment response parameters evaluated include time to nadir, nadir value, occurrence of PSA bounces (rise of ≥0.2 ng/mL followed by a subsequent fall), magnitude of bounces, duration of bounces, and correlation of bounces with clinical outcomes.
  
  
  RESULTS
  Median follow-up was 42 months (range, 36-78 months). Treatment dose levels were 45 Gy (n = 10), 47.5 Gy (n = 8), and 50 Gy (n = 29) in 5 fractions. Biochemical control rate was 98%. Median PSA at follow-up was 0.10 ± 0.20 ng/mL. Median time to nadir was 36 ± 11 months. A total of 24/47 (51.1%) patients had ≥1 PSA bounce. Median magnitude of PSA rise during bounce was 0.50 ± 1.2 ng/mL. Median time to first bounce was 9 ± 7.0 months. Median bounce duration was 3 ± 2.3 months for the first bounce and 6 ± 5.2 months for subsequent bounces. Prostate volumes <30 mL were associated with a decreased likelihood of bounce (P = .0202), and increasing prostate volume correlated with increasingly likelihood of having ≥2 bounces (P = .027). Patients reaching PSA nadir of ≤0.1 ng/mL were less likely to experience any bounce (P = .0044).
  
  
  CONCLUSIONS
  Compared with other SBRT experiences, our study demonstrated a higher PSA bounce rate, a similar or shorter median time to bounce, and a very low nadir. Prostate volume appears correlated with bounce.
authors.affiliation: University of Texas Southwestern, Dallas, Texas.
authors.forename: D Nathan
authors.initials: DN
authors.lastname: Kim
authors.affiliation: University of California San Diego, La Jolla, California.
authors.forename: Christopher
authors.initials: C
authors.lastname: Straka
authors.affiliation: University of Minnesota, Minneapolis, Minnesota.
authors.forename: L Chinsoo
authors.initials: LC
authors.lastname: Cho
authors.affiliation: University of Texas Southwestern, Dallas, Texas.
authors.forename: Yair
authors.initials: Y
authors.lastname: Lotan
authors.affiliation: University of Texas Southwestern, Dallas, Texas.
authors.forename: Jingsheng
authors.initials: J
authors.lastname: Yan
authors.affiliation: University of Colorado, Denver, Colorado.
authors.forename: Brian
authors.initials: B
authors.lastname: Kavanagh
authors.affiliation: University of Colorado, Denver, Colorado.
authors.forename: David
authors.initials: D
authors.lastname: Raben
authors.affiliation: University of Texas Southwestern, Dallas, Texas.
authors.forename: Susan
authors.initials: S
authors.lastname: Cooley
authors.affiliation: Prairie Lakes Hospital, Watertown, South Dakota.
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Brindle
authors.affiliation: University of Texas Southwestern, Dallas, Texas.
authors.forename: Xian Jin
authors.initials: XJ
authors.lastname: Xie
authors.affiliation: University of Texas Southwestern, Dallas, Texas.
authors.forename: David
authors.initials: D
authors.lastname: Pistenmaa
authors.affiliation: University of Texas Southwestern, Dallas, Texas. Electronic address: Robert.timmerman@utsouthwestern.edu.
authors.forename: Robert
authors.initials: R
authors.lastname: Timmerman
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D006801:Humans; D008297:Male; D008875:Middle Aged; D017430:Prostate-Specific Antigen / Q000097:blood*; D011471:Prostatic Neoplasms / Q000097:blood / Q000532:radiotherapy*; D016634:Radiosurgery; D011879:Radiotherapy Dosage; D016896:Treatment Outcome
chemical_list: D017430:Prostate-Specific Antigen