title: Dosimetric benefits of hemigland stereotactic body radiotherapy for prostate cancer: implications for focal therapy.
abstract: OBJECTIVE
  Compared with standard, whole-gland (WG) therapies for prostate cancer, focal approaches may provide equivalent oncologic outcomes with fewer adverse effects. The purpose of this study was to compare organ-at-risk (OAR) dosimetry between hemigland (HG) and WG stereotactic body radiotherapy (SBRT) plans.
  
  
  METHODS
  Volumetric-modulated arc radiotherapy-based SBRT plans were designed to treat the left HG, right HG and WG in eight patients, using five fractions of 8 Gy. OARs of interest included the contralateral HG, rectum, urinary bladder, urethra, penile bulb and contralateral neurovascular bundle.
  
  
  RESULTS
  Rectal V80% (the percentage of a normal structure receiving a dose of 80%) and V90% were significantly lower with HG plans than with WG plans (median values of 4.4 vs 2.5 cm(3) and 2.1 vs 1.1 cm(3), respectively, p < 0.05 by Student's t-test). Bladder V50% was also reduced significantly in HG plans (32.3 vs 17.4 cm(3), p < 0.05), with a trend towards reduction of V100% (3.4 vs 1.3 cm(3), p = 0.09). Urethral maximum dose and mean doses to the penile bulb and contralateral neurovascular bundle were also reduced significantly (42.0 vs 39.7 Gy, p < 0.00001; 13.3 vs 9.2 Gy, p < 0.05; and 40.2 vs 19.3 Gy, p < 0.00001, respectively).
  
  
  CONCLUSIONS
  Targeting an HG volume rather than a WG volume when delivering SBRT can offer statistically significant reductions for all OARs. Given the large magnitude of the reduction in dose to these OARs, it is anticipated that HG SBRT could offer a superior toxicity profile when compared with WG SBRT. This is likely to be most relevant in the context of salvaging a local failure after radiation therapy.
  
  
  CONCLUSIONS
  The dosimetric feasibility of HG SBRT is demonstrated. When compared with WG SBRT plans, the HG plans demonstrate statistically significant and large magnitude reduction in doses to the rectum, bladder, urethra, penile bulb and contralateral neurovascular bundle, suggesting the possibility of improved toxicity outcomes with HG SBRT. This is likely to be most relevant in the context of salvaging a local failure after radiation therapy.
authors.affiliation: Department of Radiation Oncology, David Geffen School of Medicine, University of California, Los Angeles, CA.
authors.forename: Amar U
authors.initials: AU
authors.lastname: Kishan
authors.affiliation: Department of Radiation Oncology, David Geffen School of Medicine, University of California, Los Angeles, CA.
authors.forename: Sang J
authors.initials: SJ
authors.lastname: Park
authors.affiliation: Department of Radiation Oncology, David Geffen School of Medicine, University of California, Los Angeles, CA.
authors.forename: Christopher R
authors.initials: CR
authors.lastname: King
authors.affiliation: Department of Radiation Oncology, David Geffen School of Medicine, University of California, Los Angeles, CA.
authors.forename: Kristofer
authors.initials: K
authors.lastname: Roberts
authors.affiliation: Department of Radiation Oncology, David Geffen School of Medicine, University of California, Los Angeles, CA.
authors.forename: Patrick A
authors.initials: PA
authors.lastname: Kupelian
authors.affiliation: Department of Radiation Oncology, David Geffen School of Medicine, University of California, Los Angeles, CA.
authors.forename: Michael L
authors.initials: ML
authors.lastname: Steinberg
authors.affiliation: Department of Radiation Oncology, David Geffen School of Medicine, University of California, Los Angeles, CA.
authors.forename: Mitchell
authors.initials: M
authors.lastname: Kamrava
mesh_terms: D006801:Humans; D008297:Male; D058958:Organs at Risk / Q000528:radiation effects*; D010413:Penis / Q000528:radiation effects; D011467:Prostate / Q000528:radiation effects; D011471:Prostatic Neoplasms / Q000532:radiotherapy*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D012007:Rectum / Q000528:radiation effects; D014521:Urethra / Q000528:radiation effects; D001743:Urinary Bladder / Q000528:radiation effects