title: Stereotactic Body Radiotherapy for Clinically Localized Prostate Cancer: Toxicity and Biochemical Disease-Free Outcomes from a Multi-Institutional Patient Registry.
abstract: OBJECTIVE
  To report on initial patient characteristics, treatment practices, toxicity, and early biochemical disease-free survival (bDFS) of localized prostate cancer treated with stereotactic body radiotherapy (SBRT) and enrolled in the RSSearch(®) Patient Registry.
  
  
  METHODS
  A retrospective analysis was conducted on patients with clinically localized prostate cancer enrolled in RSSearch(®) from June 2006 - January 2015. Patients were classified as low-risk (PSA ≤ 10 ng/ml, T1c-T2a, Gleason score ≤ 6), intermediate-risk (PSA 10.1 - 20 ng/ml, T2b-T2c, or Gleason 7), or high-risk (PSA > 20 ng/ml, T3 or Gleason ≥ 8). Toxicity was reported using Common Toxicity Criteria for Adverse Events, version 3. Biochemical failure was assessed using the Phoenix definition (nadir + 2 ng/ml). The Kaplan-Meier analysis was used to calculate bDFS and association of patient and tumor characteristics with the use of SBRT.
  
  
  RESULTS
  Four hundred thirty-seven patients (189 low, 215 intermediate, and 33 high-risk) at a median of 69 years (range: 48-88) received SBRT at 17 centers. Seventy-eight percent of patients received 36.25 Gy/5 fractions, 13% received 37 Gy/5 fractions, 6% received 35 Gy/5 fractions, 3% received 38 Gy/4 fractions, and 5% received a boost dose of 19.5-29 Gy following external beam radiation therapy. Median follow-up was 20 months (range: 1-64 months). Genitourinary (GU) and gastrointestinal (GI) toxicities were minimal, with no acute or late Grade 3+ GU or GI toxicity. Late Grade 1 and 2 urinary frequency was 25% and 8%. Late Grade 1 and 2 proctitis was 3% and 2%. Median PSA decreased from 5.8 ng/ml (range: 0.3-43) to 0.88, 0.4, and 0.3 ng/ml at one, two, and three years. Two-year bDFS for all patients was 96.1%. Two-year bDFS was 99.0%, 94.5%, and 89.8% for low, intermediate, and high-risk patients (p < 0.0001). Two-year bDFS was 99.2%, 93.2%, and 90.4% for Gleason ≤ 6, Gleason 7, and Gleason ≥ 8 (p < 0.0001). Two-year bDFS was 96.4%, 97.2%, and 62.5% for PSA ≤ 10 ng/ml, PSA 10.1 - 20 ng/ml, and PSA > 20 ng/ml (p < 0.0001). Clinical T Stage was not significantly associated with bDFS.
  
  
  CONCLUSIONS
  Early disease outcomes of SBRT for the treatment of clinically localized prostate cancer from a multicenter patient registry compare favorably with reports from single institutions. Acute and late GU and GI toxicities were minimal, and PSA response to SBRT was highly encouraging. Continued accrual and follow-up will be necessary to confirm long-term results.
authors.affiliation: Clinical Programs, The Radiosurgery Society.
authors.forename: Joanne
authors.initials: J
authors.lastname: Davis
authors.affiliation: Department of Radiation Oncology, St. Mary's Medical Center.
authors.forename: Sanjeev
authors.initials: S
authors.lastname: Sharma
authors.affiliation: Department of Radiation Oncology, Saint Francis Hospital and Medical Center.
authors.forename: Richard
authors.initials: R
authors.lastname: Shumway
authors.affiliation: Radiation Oncology, Medstar Franklin Square Medical Center, Baltimore, MD.
authors.forename: David
authors.initials: D
authors.lastname: Perry
authors.affiliation: Department of Radiation Oncology, Sir Charles Gairdner Hospital, Perth, Australia.
authors.forename: Sean
authors.initials: S
authors.lastname: Bydder
authors.affiliation: Radiation Oncology, Colorado CyberKnife, Lafayette, CO.
authors.forename: C Kelley
authors.initials: CK
authors.lastname: Simpson
authors.affiliation: Radiation Oncology, Community Medical Center-Barnabas Health ; NJ Cyberknife, Community Medical Center-Barnabas Health.
authors.forename: David
authors.initials: D
authors.lastname: D'Ambrosio
keywords: aging; disease-free survival; genitourinary malignancies; prostate cancer; prostate-specific antigen; psa; registry; sbrt; stereotactic body radiotherapy