1. CONTOURING FOR RECTAL CANCERS
Dr. Ashutosh Mukherji
Additional Professor
Department of Radiotherapy,
Regional Cancer Centre, JIPMER

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Importance of Depth of invasion
Kikuchi R, Dis Colon Rectum, 1995 (12):1286-95

7. Role of imaging in early lesions
• Confirm that
muscularis propria
thickness is preserved
• Identify sites of
disease within the
mesorectum
• Final decision
regarding
appropriateness of
local excision is driven
by Histopathology
assessment of risk
factors of the excised
lesion
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8. • Location of tumour – anterior,
posterior, r or l lateral
• Morphology: annular, semi
annular, polypoidal,
ulcerating, mucinous, villous
• For annular/ulcerating –
location of central invasive
portion vs raised edges
• For polypoidal/villous lesions
– site of stalk
• Invasive margin: nodular
infiltrating, broad based
pushing margin
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• Submucosa visible at invasive
edge? – T1
• Submucosa not visible at
invasive edge but good
thickness of muscularis propria
visible? T1 (sm3)/early T2
• Part of muscularis propria
visible? = T2
• No muscularis propria visible
but intermediate signal
intensity does not project
beyond contour of bowel = T2
full thickness/T3a
• Tumour projecting beyond
muscularis propria = T3

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Finding the nodes

11. How MR Imaging helps in contouring
rectal cancers
• To assess bulky polyps >5mm thick
• Initial assessment of disease remote from the lumen
within entire mesorectum
• Identification of pelvic sidewall disease
• Identify site location of stalk or invasive border and
relationship to puborectalis sling, peritoneal
reflection, mesorectal or intersphincteric border
• Identification of high risk patients with extramural
venous invasion
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13. Rectal Cancer Radiotherapy Contouring
Guideline for clinical target volumes (CTV) for neoadjuvant
chemoradiotherapy in locally advanced rectal cancer: gross tumor,
peri-rectal, pre-sacral, internal iliac and external iliac.
NTUH practice:
• GTV: main tumor mass + involved lymph nodes
• CTV:
– GTV with 15 mm expansion
– Distal 20 mm margin to GTV for CTV
– Vessels with 7 mm expansion
– Contour CTV to include mesorectum and pre-sacrum
– Avoid bone and small bowel
Int J Radiat Oncol Biol Phys. 2009 Jul 1;74(3):824-30. doi: 10.1016/j.ijrobp.2008.08.070.

14. RTOG CONSENSUS PANEL RECOMMENDATIONS
• Risk volumes defined as
CTVs: these were local and
nodal.
• Local CTV included
mesorectum, presacrum,
scar tissue and
anastomosis.
• Nodal CTV included
perirectal, iliac (external
and internal) and inguinal.
• Nodal CTVs:
– CTVA: internal iliac,
presacral and peri-rectal
– CTVB: external iliac
– CTVC: inguinal
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https://www.rtog.org/CoreLab/ContouringAtlases/Anorectal.aspx;
Myerson et al. IJROBP 2009

15. International consensus guidelines on Clinical
Target Volume delineation in rectal cancer
• Consensus was obtained for delineation of the CTV
for elective irradiation of all regional lymph node
levels.
• Seven subsites at risk were identified: presacral
space (PS), mesorectum (M), lateral lymph nodes
(LLN), external iliac nodes (EIN), inguinal nodes (IN),
ischiorectal fossa (IRF) and sphincter complex (SC).
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Radiotherapy and Oncology 120 (2016) 195–201
http://dx.doi.org/10.1016/j.radonc.2016.07.017

16. IMMOBILIZATION DEVICES
• BELLY BOARD

17. Schematic presentation of belly board surface
• Belly board : in region of pelvis, the board has raised surface
…. To separate pelvic and abdominal structures
• Abdominal area has depression : to accommodate the bowel
loops……so that the intestines do not displace pelvic
structures.

18. Simulation Protocol
• Full bladder
• Prone on bowel displacement device (if can
do daily OBI or equivalent)
• Anal marker & wire on distal edge of tumor if
possible
• IV & oral contrast
• 2.5 to 5 mm CT slices
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Contouring the GTV
• Scroll through slices
to view extent of
tumor.
• Start your contour
where the tumor is
obvious
• Check your volume
against exam /
colonoscopy findings
since imaging is less
sensitive

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22. Lowest boundary of GTV
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Measure the
distance from
the GTV to
anal verge

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In the SAGITTAL view, use
the measuring tool to check
the vertical extent of the GTV
contour.

25. Differentiating a lymph node from a vessel
1. Use MRI overlay
2. Scroll up and down: nodes will be rounded
structures that disappear then reappear
3. Contour the vessels before contouring the GTV
4. Sub-centimeter perirectal nodes are contoured in
the GTV to show you they are in the standard CTV.
These DO NOT need to be contoured unless grossly
enlarged.
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Enlarged
perirectal
lymph node

27. • Now turn off ALL contours
• Start at abdominal aorta
• Scroll inferiorly, following
branches
• Lymph nodes sit on vessels.
This is why we contour
vessels in nodal CTV
• Sequence of vessels:
– Aorta (artery) or IVC (vein) 
Common Iliacs (R and L) 
Internal iliac (go posterior/in
front of sacrum) and External
Iliacs (go anterior  become
inguinal/femoral when exit
pelvis)
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Review anatomy of pelvic vessels

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31. • Lymph node metastasis
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33. • Lymph node metastasis, bifurcation of iliacs
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34. • Common iliacs
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35. What is the CTV?
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This is the RTOG 2009 Consensus Recommendation

36. Caudal (inferior) extent of CTV
(Muscles and connective tissue of pelvic floor are better
visualized with MRI)
1. CTV should extend at
least to the pelvic floor,
even if upper rectal
cancer
2. Extend to a minimum
of 2cm caudad to GTV
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Mesorectum (peri-rectal)
Pelvic floor, Levator ani

37. • Lower boundary of CTV
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38. CTV in the
lower
pelvis
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Posterior and lateral
margins: Extend to
lateral pelvic
muscles or bone
Anterior margin: Extend
into prostate/seminal
vesicles in a male (vagina
for female)

39. CTV IN
Lower
Pelvis
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40. CTV in
Mid-pelvis
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CTVA covers: Rectum,
Mesorectum, Internal iliac
vessels, Presacral space
Mesorectum Presacral space
Anterior margin: Extends
1 cm into Posterior bladder
wall

41. CTV IN
Mid-Pelvis
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42. CTV in
Upper-pelvis
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DO NOT include
muscle or boneInclude internal
iliac arteries and
veins; posterior
border of CTV
abuts external iliac
vessels (which we
do NOT include
unless T4 tumor
invading prostate or
vaginal
anteriorly)
Presacral space
Lymph Nodes

43. Superior
Extent of CTV
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Continue contour up
to where the
common iliacs
bifurcate OR L5/S1
interspace

44. CTV IN
Upper
Pelvis
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45. Designation of regions at risk of
recurrence and their contouring
• The International working group identified following
subsites for risk of nodal recurrence:
– Presacral nodes (PN),
– Mesorectum (M),
– Lateral lymph nodes (LLN),
– External iliac nodes (EIN),
– Ischio-rectal fossa (IRF),
– Sphincter complex (SC),
– Inguinal Nodes (IN)
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Anterior border of the posterior lateral node (purple),
when the ureters join the bladder (red line)

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Caudal border of the external iliac nodes (orange),
where the deep circumflex vein crosses the external
iliac artery

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Cranial border of the ischio-rectal fossa (blue), where
the inferior pudendal artery leaves the pelvis going
into the Alcock’s canal

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Caudal border of the ischio-rectal fossa (blue), at
the inferior level of the sphincter complex and the
ischial tuberosity

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Elective subsites to be included in CTV according to
stage and tumour location
Mesorectum; PS = Pre-sacral space; LLN = Lateral lymph nodes

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EIN=External iliac nodes; IRF = Ischio-rectal fossa; SC =
Sphincter complex
Elective subsites to be included in CTV according to
stage and tumour location

59. When a CTV Boost is required
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Extend CTV to cover entire
mesorectum and presacral
region at level of GTV, with
a minimum 2cm margin on
GTV in the cephalad and
caudad directions
Add a margin of 7-10 mm
for PTV to the various CTVs

60. PTV from
the CTV
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Add a margin of 7-10 mm
for PTV to the various CTVs

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SAGITTAL VIEW CORONAL VIEW
Always check final volumes in sagittal and coronal views to
make that the contoured volume makes sense in 3 dimensions

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DOSE CONSTRAINTS

63. Pre-operative vs. Post-operative Therapy
• Approach 1 – Post-operative radiation
– Surgical resection
– If T3/4 and/or N1/2  post-operative chemoradiation 
chemotherapy
• Approach 2 – Pre-operative radiation
– U/S / MRI T3/4 cancer or clinical T4
– Pre-operative therapy  surgery  chemotherapy
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Effect of Field Volume: Short course
versus Long Course RT

65. • Pre-operative radiotherapy has generally been better
tolerated than postoperative. This was also seen in the single
trial comparing pre- and postoperative radiotherapy.
• In all pre-operative trials irrespective of whether conventional
fractions of about 2 Gy or high fractions of 5 Gy were used,
more perineal complications after an abdominoperineal
resection were seen in irradiated patients
• Increased risk of postoperative ileus has been seen in trials
irradiating large volumes of small bowel, either pre-op or
postop but not when smaller volumes were irradiated
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68. Post-operative Therapy: Who needs
treatment?
• T3 or greater Or N+
Gunderson LL, et al. JCO 2004;22:1785-96
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69. • Low-risk patients (LRR <10%) are recommended TME
alone,
• intermediate-risk patients (LRR 10%–20%) are
advised preoperative SCRT followed by TME and
adjuvant chemotherapy as standard treatment,
• high-risk patients (LRR >20%) are recommended
preoperative CRT followed by TME and adjuvant
chemotherapy.
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70. TAKE HOME MESSAGE

71. Contouring guideline
 GTV: main tumor mass + involved lymph nodes
 CTV:
– GTV with 15 mm expansion
– Distal 20 mm margin to GTV for CTV
– Vessels with 7 mm expansion
– Contour CTV to include mesorectum, lateral nodes, External
and internal iliac nodes, pre-sacrum, ischiorectal fossa,
sphincter complex and inguinal nodes where required
– Avoid bone and small bowel
– Boost CTV where required with a minimum 2cm margin on
GTV in the cephalad and caudad directions
 PTV: 7-10 mm margin to the CTV
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72. According to Roel’s:
• The CTV should encompass the tumor, the MS, and the PPS in
all cases. The Inferior pelvis is at risk if the tumor is located
within 6 cm from the anal margin and the surgeon aims at a
sphincter-saving procedure, or the tumor invades the anal
sphincter and an APR is necessary.
• MLN and the LLN are included into the CTV for all patients.
• The obturator nodes should be included when the tumor is
located <10 cm from the anal margin.
• The External iliac LN should be part of the CTV only when
anterior organ involvement is highly suspected
• Inguinal LN should be part of the CTV only when the tumor
invades the lower third of the vagina or there is major tumor
extension into the internal and external anal sphincter.
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73. Pertinent articles for reference
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74. Thank you