title: Prostate-specific antigen kinetics after primary stereotactic body radiation therapy using CyberKnife for localized prostate cancer.
abstract: OBJECTIVE
  To assess prostate-specific antigen (PSA) kinetics and report on the oncologic outcomes for patients with localized prostate cancer treated with stereotactic body radiation therapy (SBRT) using CyberKnife.
  
  
  METHODS
  We extracted the list and data of 39 patients with clinically localized prostate cancer who had undergone primary SBRT using CyberKnife between January 2008 and December 2012 from the Smart Prostate Cancer database system of Seoul St. Mary's Hospital. Changes in PSA over time, PSA velocity, and PSA nadir were evaluated from the completion of SBRT using CyberKnife. Biochemical recurrence (BCR)-free survival after primary SBRT using CyberKnife was determined using Kaplan-Meier analysis.
  
  
  RESULTS
  The rate of PSA decrease was maximal in the first month (median -3.34 ng/mL/mo), which then fell gradually with median values of -1.51, -0.32, -0.28, -0.20, and -0.03 ng/mL/mo for durations of 3, 6, 9, 12, and 24 months after SBRT using CyberKnife, respectively. The median PSA nadir was 0.31 ng/mL after a median 23 months. Kaplan-Meier analysis calculates an actuarial 5-year BCR-free survival after SBRT using CyberKnife as 80.8%.
  
  
  CONCLUSIONS
  PSA decline occurred rapidly in the first month, and then the rate of PSA decline fell off steadily over time throughout 2 years after treatment. Also, SBRT using CyberKnife leads to long-term favorable BCR-free survival in localized prostate cancer.
authors.affiliation: Department of Urology, Seoul St. Mary's Hospital, The Catholic University of Korea College of Medicine, Seoul, Republic of Korea.
authors.forename: Yong Hyun
authors.initials: YH
authors.lastname: Park
authors.affiliation: Department of Medical Informatics, The Catholic University of Korea College of Medicine, Seoul, Republic of Korea.
authors.forename: In Young
authors.initials: IY
authors.lastname: Choi
authors.affiliation: Department of Radiation Oncology, Bucheon St. Mary's Hospital, The Catholic University of Korea College of Medicine, Bucheon, Republic of Korea.
authors.forename: Sei Chul
authors.initials: SC
authors.lastname: Yoon
authors.affiliation: Department of Radiation Oncology, Seoul St. Mary's Hospital, The Catholic University of Korea College of Medicine, Seoul, Republic of Korea.
authors.forename: Hong Seok
authors.initials: HS
authors.lastname: Jang
authors.affiliation: Department of Urology, Seoul St. Mary's Hospital, The Catholic University of Korea College of Medicine, Seoul, Republic of Korea.
authors.forename: Hyong Woo
authors.initials: HW
authors.lastname: Moon
authors.affiliation: Department of Urology, Seoul St. Mary's Hospital, The Catholic University of Korea College of Medicine, Seoul, Republic of Korea.
authors.forename: Sung-Hoo
authors.initials: SH
authors.lastname: Hong
authors.affiliation: Department of Urology, Seoul St. Mary's Hospital, The Catholic University of Korea College of Medicine, Seoul, Republic of Korea.
authors.forename: Sae Woong
authors.initials: SW
authors.lastname: Kim
authors.affiliation: Department of Urology, Seoul St. Mary's Hospital, The Catholic University of Korea College of Medicine, Seoul, Republic of Korea.
authors.forename: Tae-Kon
authors.initials: TK
authors.lastname: Hwang
authors.affiliation: Department of Urology, Seoul St. Mary's Hospital, The Catholic University of Korea College of Medicine, Seoul, Republic of Korea.
authors.forename: Ji Youl
authors.initials: JY
authors.lastname: Lee
keywords: Localized prostate cancer; PSA kinetics; Stereotactic body radiation therapy