6. Treatment

Purpose & types of Colorectal cancer treatments

What is the treatment modality used on most colorectal cancer patients?

Surgery

What is the treatment of choice for colorectal cancer?

Surgery

What are the 3 surgery techniques used?

1. Anterior Resection

2. APR

3. Surgery + Multi-agent chemo

What is Anterior Resection?

• en bloc tumor removal + lymph node dissection

• Bowel is reanastomosed (reattached)- so colostomy is not required

What does APR stand for?

Abdominoperineal Resection

On what patients is APR used?

• rectal cancer in lower 3rd of rectum 

• Removes anus so colostomy required 

What is “surgery + multi-chemo agent” used for

colon above the sigmoid

T/F: Colon cancer is chemosensitive

False: its chemoresistant

What type of chemo is given to colorectal patients as a chemosensitizer

1. 5-FU

2. Gemitabine

What are the 2 purposes of delivering RTT to colorectal cancer patients?

1. Most commonly as: Post-Op adjuvant to surgery

2. RTT + Chemo for disease that is:

   1. Medically inoperable

   2. Locally advanced unresectable cancer

What is the major advantage of post-op RTT adjuvant to surgery?

The physician has:

1. pathologic confirmation &

2. extent of tumor spread to lymph nodes or distant mets

Types of RTT used:

1. Endocavitary RTT w/ KV (contact therapy)

2. MV RTT: 3 or 4 field + Boost

3. IORT boost

What is the purpose of using Endovacitary RTT?

To possibly offer a sphincter-preserving technique for patients with distal rectal cancers confined to the bowel wall 

Endocavitary RTT

1. dose

2. number of treatments

1. Dose/ Treatment: 30Gy

2. # of txs: 4 txs, 2 weeks apart each

FYI:

week 0: 30 Gy
week 2: 30 Gy

week 4: 30Gy

week 6: 30 Gy

For MV treatments to treat colorectal cancer, What areas do we treat?

1. Primary tumor, and

2. Pelvic nodes

Via a boost field/ shrinking field

Field arrangments for colorectal cancer

Option 1: 3 field prone: 1 PA + 2 lats w/ wedges

Option 2: 4 field: AP, PA, 2 lats

Which field arrangement for colorectal cancer causes more bladder irradiation?

4 field 

Field borders for 4 field for colorectal cancer

AP/PA fields

• Superior: L4/5 interspace (disc space) or Smoke Stack

• Inferior: Just below obturator foramen; 2 cm + margin from the tumor

• Lateral: 2cm lateral to pelvic side wall (FY: so you tx iliac nodes)

Field borders for 4 field for colorectal cancer

Lateral fields (assuming 3 field technique)

• Anterior: symphysis pubis; ensuring tx of external iliac nodes

• Posterior: 1.5-2.0 cm behind the anterior bony sacral margin

What organs do we protect using a 3 field technique/

1. remaining bowel

2. bladder

3. bone marrow

SIM markings for colorectal cancer

1. BB on anal verge- perineal reference

2. Iodine contrast-soaked tampon- vagina reference

Dose for MV technique for colorectal cancer patients and # of weeks

50-55Gy; higher doses if small bowel can be excluded from field

6-5.5 wks

What does IORT stand for?

Intraoperative Radiation Therapy

What is IORT used for?

Boost technique 

What dose is used for IORT for colorectal cancer?

10-20 Gy in a single fraction

T/F:IORT is a better boost than a shrinking field technique

False: it has higher toxicity, does not show improvement in survival, and contraindicated in patients with distant mets

RADIATION SIDE EFFECTS

What is the primary dose-limiting structure for colorectal cancer patients?

small bowel (fyi: causes diarrhea)

If treating lesion in ascending or descending colon, dose-limiting structures include

kidney and small bowel

What are severe effects of RTT to treat colon cancer?

1. adhesions

2. enteritis

3. obstruction

What treatment devices can be used to displace the small bowel?

1. belly-board

2. false table-top 

Bladder should be (empty/full) when treating colorectal cancer with RTT. WHy?

full

to displace small bowel

Other side effects when treating colorectal cancer with RTT

Acute/ Brisk erythema in gluteal fold