Pelvis Contouring

• True / False: prostate has a GTV

  • FALSE: use CTV instead
• Low risk prostate: prostate only

  Intermediate risk prostate: prostate + proximal seminal vesicles

  High risk prostate: prostate + seminal vesicles + pelvic lymph nodes
• Prostate:

  • PTV margin: 1 cm
  • conventional fractionation: 78 Gy / 39 fractions
  • moderate hypo fractionation:
  • low / int risk: 60 Gy / 20 fractions
  • high risk: 68 Gy / 25 fractions
• distal common iliac: L5 / S1
• external iliac: stop at top of femoral heads
• obturator: stop at pubic symphysis
• pre sacral: contour in front of S1 and S2 vertebrae and stop when you see piriformis muscle
• seminal vesicles:

  • proximal: within 1 cm of prostate
  • distal
• Elective lymph nodes:

  • 7 mm around vessels
  • crop out: bowel, bladder, muscles, bone
• Prostate Imaging:

  • daily CBCT
  • match to prostate rectal interface
• Typical Rectal Treatment:

  • chemo RT → 7 - 10 week break → surgery (total mesorectal incision)
  • short course:
  • 25 Gy / 5 fractions
  • no chemo
  • wait 1 week → surgery
  • long course:
  • rectal tumour: 50 Gy / 25 fractions
  • mesorectum + elective lymph nodes: 45 Gy / 25 Gy
  • concurrent chemo = capecitabine (2 x a day, on days of RT)
  • wait 7 - 10 weeks → surgery
• Rectum sim prep:

  • 1 hour prior: 500 cc of water → fill bladder
  • 45 mins prior: omnipaque (small bowel contrast)
• Rectal Sim Setup:

  • supine
  • hands on chest (grip ring)
  • knee and ankle rest
  • anal verge marker +/- scar wire (post op)
• Purpose of chemoRT then surgery for rectum:

  • decrease local recurrences
  • preserve sphincter
  • BUT: does not alter survival
• Rectal:

  • GTV: rectal tumour (use MRI to view)
  • CTV 50: rectal tumour (GTV) + margin for microscopic extension (2 cm)
  • crop out: bone, muscle, small bowel
  • CTV 45:
  • mesorectum
  • sup: sacral promontory (L5 / S1)
  • inf: pelvic floor
  • ant: into bladder / vagina / prostate by 1 cm
  • elective lymph nodes
  • perirectal
  • obturator
  • internal iliac
  • pre sacral
  • PTV: CTV + 0.5 cm (set up variability)
• Rectal:

  • don't include:
  • external iliac (unless T4 tumour)
  • inguinal (maybe if low in anal canal)