Pre-TME era

Mesorectal subsite/LN ALWAYS included in CTV

Mesorectal subsite / LN region

Lateral pelvic subsite / LN region Cranial: bifurcation common iliac arteries

Caudal: level were obturator artery enters obturator canal

Anterior: ureter

Includes LN along pelvic side wall:

internal iliac artery + middle rectal artery +/-obturator artery

Lateral pelvic subsite / LN region

Lateral subsite/LN ALWAYS included in CTV

Obturator nodes ONLY included in CTVIf Tumor < 10 cm

Lateral pelvic subsite / LN region

Steup et al (EJC,2002): LN along the obturator artery

0% (0/133)

3% (3/99)

9% (33/373)

Posterior pelvic subsite

Presacral space

Includes LN along sacral vessels, inferior hypogastric plexus

Posterior subsite ALWAYS included in CTV

Posterior pelvic subsite

Inferior pelvic subsitetriangle of the perineum containing

sfinctercomplex

perianal/ ischiorectal space

Discussion inferior pelvic subsite

APR: 11 % ALWAYS include in CTV

T< 6 cm: 8 %

T> 6 cm : 3 % NOT include in CTV

T>11 cm: 0%

Inferior pelvic subsite

Low Risk locations for local failure

Anterior pelvic subsiteIncludes all organs ventrally of the mesorectal subsite

Anterior subsite ONLY included in CTV

if invasion anterior organ (prostate, bladder,…)

Anterior pelvic subsite

External iliac + inguinal LN

External iliac LN ONLY included in CTV If anterior organ invasion Inguinal LN ONLY included in CTV If massive invasion anal margin If invasion lower third vagina

Discussion External iliac LN45 patients with T4 rectal cancer preoperative CRT without elective external iliac node RT

no recurrences in external LN region!

Sanfilippo et al, Int J Rad Onc Biol Phys 2001

Upward LN regionIncludes inf. mesenteric artery +/- sup. rectal artery

Upward LN region NOT included in CTV because….

Upward LN region

□ No sign. difference in survival !

□ Not sign. more diarrhea □ Sign. more hematological and liver complications.

All patients : CTV = Posterior PS + Mesorectal PS/LN + Lateral PS/LN

□ Inferior PS: tumor < 6 cm from anal margin +/- APR □ Obturator LN: tumor < 10 cm from anal margin □ External iliac LN tumor invades anterior organ □ Anterior PS □ Inguinal LN: tumor invades lower third vagina or massive anal invasion

Delineation clinical target volume

+/-

Delineation clinical target volume

Consensus on clinical target volume regions

BUT…

No Consensus on anatomical borders !

Atlas for pelvic LN delineation

Can we use pelvic blood vessels as a surrogate for delineation of

lymph node regions?

Goal + Methods

GOALto map pelvic normal LN to determine appropriate margins around blood vessels to

cover LN

METHODS20 patients with gynaecologic tumorsMRI MRI + USPIOPelvic nodes contoured on USPIO MRIMargins of 3, 5, 7, 10 and 15 mm around blood vessels 5 CTV’s

Results

Modified 7 mm margin: 99% LN covered100% coverage of internal iliac LN: lateral border enlarged to pelvic sidewall99% coverage of obturator LN:width of 18 mm along the pelvic sidewallpresacral LN: too few nodes to draw conclusions

Remaining problem

Anterior border of the obturator LN region ?

internal iliac a.

obturator a.

common iliac a. external iliac a.

Remaining problem

Delineation of all internal iliac branches in the pelvis ?