55 y/o M with favorable intermediate risk prostate adenocarcinoma (cT1cN0M0, Gleason 3+4, PSA 9, 5/12 cores involved bilaterally).



  • He was treated with SBRT alone.
  • IGRT with kV image guidance based on implanted fiducials with a SpaceOAR in place.
  • Daily CBCT would be appropriate for LINAC based SBRT.

DOSE: He received 3625cGy with 6MV photons delivered every other day. 

SIMULATION: He was simulated supine with a comfortably full bladder and empty rectum in a vac-lock bag. MR simulation or fusion of diagnostic MRI will also assist in target and OAR delineation.





Case contributed by Leonid Reshko from the University of Louisville

RT coverage (per NRG GU-005 protocol):

  • CTV = prostate
  • PTV = CTV + 3 mm posteriorly (towards rectum) and 5 mm in other directions
  • Prostate apex is located at the GU diaphragm


OAR delineation:

  • Bladder should be contoured from its base to the dome.
  • Rectum should be contoured from the anus (at the level of the ischial tuberosities) for a length of 15 cm or to the recto sigmoid flexure.
    • This generally is below the bottom of the sacroiliac joints.
  • Femoral_Head_L/R should be contoured from the acetabulum to the inferior aspect of the pubic symphysis.
  • Spc_Bowel should be the ‘bowel bag’ contour defined as the volume where moveable bowel can reside within the peritoneal cavity
  • PenileBulb - reference the eContour Intact Prostate module or Pelvic OAR guidelines.
  • Urethra - reference Urethral contouring guidelines.

Prostate SBRT is currently recommended as monotherapy for patients with low and favorable intermediate risk prostate cancer, per Jackson et al. IJROBP 2019. Ongoing prospective trials such as NRG GU-005 and HEAT are assessing non-inferiority of prostate SBRT vs moderately hypofractionated RT.


OAR Constraints (ideal – variable acceptable):

  • Rectum D0.03cc[Gy] <= 38.06-40
  • Rectum D3cc[Gy] <= 34.4-36
  • Rectum D10%[Gy] <= 32.63-34
  • Rectum D20%[Gy] <= 29-30
  • Rectum D50%[Gy] <= 18.13-19
  • Bladder D0.03cc[Gy] <= 38.06-40
  • Bladder D50%[Gy] <= 18.12-20
  • Spc_Bowel D0.03[Gy] <= 30-33
  • Urethra D0.03cc[Gy] <= 38.78-43.5.
    • Visualization of the urethra is required for patients where the maximum point dose to a point that is 0.03 cc exceeds 38.78 Gy.
  • PenileBulb D0.03cc[%] <= 100
  • PenileBulb D3cc[%] <= 55 (19.9 Gy)
  • Femurs D10cc[%] <= 43 (15.6 Gy)
  • Femurs D1cc[%] <= 55 (19.9 Gy)