title: The Impact of Obesity on Patient Reported Outcomes Following Stereotactic Body Radiation Therapy for Prostate Cancer.
abstract: OBJECTIVE
  The relationship between obesity (Body Mass Index ->30 kg/m(2)) and quality of life (QoL) following prostate cancer (PCa) radiation therapy (RT) is unknown. Excess abdominal fat may compromise the precise delivery of radiation, putting surrounding organs at risk for greater radiation exposure. Stereotactic body radiation therapy (SBRT) utilizes a real-time tracking system that provides updated prostate position information and allows for correction of the therapeutic beam during treatment with high accuracy. In this study, we evaluate the impact of obesity on patient reported outcomes following SBRT for prostate cancer.
  
  
  METHODS
  Between February 2008 and April 2012, 88 obese and 178 non-obese patients with PCa were treated with SBRT at Georgetown University Hospital, Washington, DC. Health-related quality of life (HRQol) was assessed via the expanded prostate cancer index composite (EPIC)-26 at baseline, 6, 12, 18, and 24 months after 5-fraction delivery of 35-36.25 Gy with the CyberKnife. Patients who received androgen deprivation therapy (ADT) were excluded from this analysis due to its known negative impact on HRQoL.
  
  
  RESULTS
  Pretreatment characteristics of obese and non-obese patient groups were similar except that obese patients had lower total testosterone levels. Urinary and bowel function and bother scores between the two patient cohorts were comparable at baseline and subsequent follow-ups. Sexual function and bother were also similar at baseline between both groups. Bother was defined by displeasure patients may experience from functional decline. At 24 months post-SBRT, obese men experienced borderline clinically significant decrease in sexual function and greater sexual bother compared to non-obese patients. Fatigue was significantly higher in obese patients compared to non-obese patients at 18 months post-SBRT.
  
  
  CONCLUSIONS
  Prostate SBRT affects obese and non-obese patients similarly in total HRQoL scores and majority of its domains. Obesity has been associated with cancer recurrence; therefore longer follow-up is required to determine the impact of obesity on cancer control.
authors.affiliation: Department of Radiation Medicine, Georgetown University Hospital.
authors.forename: Harsha
authors.initials: H
authors.lastname: Koneru
authors.affiliation: Department of Radiation Medicine, Georgetown University Hospital.
authors.forename: Robyn
authors.initials: R
authors.lastname: Cyr
authors.affiliation: National Institute of Nursing Research, National Institutes of Health.
authors.forename: Li Rebekah
authors.initials: LR
authors.lastname: Feng
authors.affiliation: Department of Radiation Medicine, Georgetown University Hospital.
authors.forename: Edward
authors.initials: E
authors.lastname: Bae
authors.affiliation: Department of Radiation Medicine, Georgetown University Hospital.
authors.forename: Malika T
authors.initials: MT
authors.lastname: Danner
authors.affiliation: Department of Radiation Medicine, Georgetown University Hospital.
authors.forename: Marilyn
authors.initials: M
authors.lastname: Ayoob
authors.affiliation: Department of Radiation Medicine, Georgetown University Hospital.
authors.forename: Thomas M
authors.initials: TM
authors.lastname: Yung
authors.affiliation: Department of Radiation Medicine, Georgetown University Hospital.
authors.forename: Siyuan
authors.initials: S
authors.lastname: Lei
authors.affiliation: Department of Radiation Medicine, Georgetown University Hospital.
authors.forename: Brian T
authors.initials: BT
authors.lastname: Collins
authors.affiliation: National Institute of Nursing Research, National Institute of Health.
authors.forename: Leorey
authors.initials: L
authors.lastname: Saligan
authors.affiliation: Department of Radiation Medicine, Georgetown University Hospital.
authors.forename: Suy
authors.initials: S
authors.lastname: Simeng
authors.affiliation: Deptartment of Biological & Environmental Sciences, University of the District of Columbia.
authors.forename: Deepak
authors.initials: D
authors.lastname: Kumar
authors.affiliation: Department of Radiation Medicine, Georgetown University Hospital.
authors.forename: Sean P
authors.initials: SP
authors.lastname: Collins
keywords: bmi; cyberknife; epic; obesity; organ confined prostate cancer; sbrt