TECHNIQUE: He was treated with pre-op hypofractionated 3D-CRT with sequential chemo (capecitabine + oxaliplatin x 6 cycles) prior to total mesorectal excision (TME).
DOSE: He received 25 Gy in 5 fractions to peri-rectal, pre-sacral, and internal iliac nodes, with no boost to the primary/mesorectum.
SIMULATION:
IV contrast can help visualize vessels though not required (this patient had no IV contrast but extensive calcifications in vessels)
Radiopaque marker should be placed at the anal verge
Bladder comfortably full to help decrease small bowel dose
Consider small bowel and/or rectal contrast (optional)
Some institutions use prone position (belly board)
If using IMRT, supine position may be more reproducible
TECHNIQUE: Hypofractionated IMRT, with sequential adjuvant chemo prior to TME
DOSE: 20 Gy in 5 fractions to elective nodal target volume (per RTOG anorectal atlas), with 25 Gy in 5 fractions SIB to rectum and mesorectal compartment at levels of gross disease
Case contributed by National Cancer Institute / National Capital Consortium
CTV = rectum and mesentery; peri-rectal, pre-sacral, internal iliac nodes*
Superiorly: bifurcation of internal iliac and external iliac arteries (~S1/S2). If any pre-sacral LN or internal iliac LN are involved, then CTV should be at least > 1 cm above most cranial pathologic LN.
Lateral border of mesentery: pelvic sidewall (muscle/bone)
Anteriorly: 1 cm into posterior bladder (for bladder variation above vagina/prostate) and include posterior portion of obturator nodes
Inferiorly: entire mesorectum to pelvic floor (even for upper rectal primary); ≥ 2cm inferior to gross disease; <3mm beyond levator ani (unless levator ani involved, then 1-2cm mgn up to bone)
*Include external iliacs only if tumor extends to prostate/vagina (T4 tumor per AJCC)
External iliac vessels + 7-10 mm margin including small nodes
*If growth into distal vagina or growth into anal canal and distal to dentate line, include inguinals for anal canal involvement (controversial, inguinal nodes are metastatic in rectal cancer)
Avoid covering entire ischio-rectal fossa and anal canal unless tumor invades levators or anal canal, as additional toxicity is added
CTV 25 = rectum and the mesorectal compartment over the length of involved rectum and peri-rectal LN, with a 1-cm margin cephalad and caudad
3D-CRT or IMRT are both considered standard of care for 5 Gy x 5 hypofractionated rectal radiation (RTOG 0822 showed IMRT did not reduce GI toxicity with conventionally fractionated RT).
Benefits of short-course RT:
Fewer visits for RT --> Increased cost effectiveness and decreased patient financial toxicity
Shorter time to diverting ileostomy time (if patient has been previously diverted)
Increased compliance with chemo
May allow for total neoadjuvant therapy (TNT) to spare post-op chemo toxicity
Response to neoadjuvant chemotherapy may help guide post-operative adjuvant treatment options
Anatomy:
Rectum is ~15-16 cm long, starts ~S3
Rectum subdivided according to distance from anal verge during rigid sigmoidoscopy:
Upper 1/3: 12-16 cm
Middle 1/3: 6-12 cm
Lower 1/3: < 6 cm
Anterior peritoneal reflection is point at which rectum exits peritoneal cavity and becomes a retroperitoneal structure (12-15 cm from anal verge)