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 CTV If 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 subsite triangle 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 subsite Includes 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 LN 45 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 region Includes 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 GOAL to map pelvic normal LN to determine appropriate margins around blood vessels to cover LN METHODS 20 patients with gynaecologic tumors MRI MRI + USPIO Pelvic nodes contoured on USPIO MRI Margins of 3, 5, 7, 10 and 15 mm around blood vessels 5 CTV’s

Results Modified 7 mm margin: 99% LN covered 100% coverage of internal iliac LN: lateral border enlarged to pelvic sidewall 99% coverage of obturator LN: width of 18 mm along the pelvic sidewall presacral 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 ?