EOR GI part 6- colorectal CA Flashcards
What is colorectal carcinoma?
Adenocarcinoma of the colon or rectum
What is the incidence of colorectal carcinoma?
Most common GI CA
2nd most common Ca in the US
Incidence increases with age starting at 40 and peaks at 70-80 yrs
How common is colorectal carcinoma as a cause of CA deaths?
2nd most common cause of CA deaths
What is the male: female ratio of colorectal CA?
~1:1
What are the dietary RFs of colorectal CA?
Low-fiber, high-fat diets correlate with increased rates
RFs of colorectal CA: genetic
FHx
- FAP
- Lynch syndrome
RFs of colorectal CA: IBD
Ulcerative colitis>Crohn’s dz
Age
Previous colon CA
What is Lynch syndrome?
HNPCC- Hereditary NonPolyposis Colon Cancer
Autosomal dominant inheritance of high risk for development of colon CA
What are the current ACS recommendations for polyp/colorectal screening in asymptomatic pts without family (first-degree) hx of colorectal CA?
Starting at age 50, at least one of the following test regimens is recommended:
- Colonoscopy every 10 yrs
- Double contrast barium enema (DCBE) every 5 years
- Flex sigmoidoscopy every 5 years
- CT colonography every 5 years
What are the current recommendations for colorectal CA screening if there is hx of colorectal CA in a first-degree relative <60 yo?
Colonoscopy at age 40, or 10 years before the age at dx of the youngest first-degree relative, and every 5 yrs thereafter
What s/sx are associated with right-sided lesions?
R side of bowel has a large luminal diameter, so a tumor may attain a large size before causing problems Microcytic anemia Occult/melena more than hematochezia PR Postprandial discomfort Fatigue
What s/sx are associated with left-sided lesions?
L side of bowel has smaller lumen and semisolid contents Change in bowel habits (small caliber stools) Colicky pain Signs of obstruction Abdominal mass Heme pos or gross red blood Nausea Vomiting Constipation
What is the incidence of rectal CA?
Comprises 20-30% of all colorectal CA
What are the s/sx of rectal CA?
MC sx is hematochezia or mucus Also: Tenesmus Feeling of incomplete evacuation of stool Rectal mass
What is the DDx of a colon tumor/mass?
Adenocarcinoma Carcinoid tumor Lipoma Liposarcoma Leiomyoma Leiomyosarcoma Lymphoma Diverticular dz Ulcerative colitis Crohn's Polyps
Which diagnostic tests are helpful for colorectal CA?
Hx and PE Heme occult CBC Barium enema Colonoscopy
What dz does microcytic anemia signify until proven otherwise in a man or postmenopausal woman?
Colon CA
What tests help find metastases?
CXR (lung metastases)
LFTs (liver metastases)
Abd CT scan (liver metastases)
Other tests based on hx and PE
What is the preop workup for colorectal CA?
Hx PE LFTs CEA CBC Chem 10 PT/PTT Type and cross 2 units of PRBCs UA Abdominopelvic CT scan
By what means does colorectal CA spread?
Direct extension: circumferentially and then through bowel wall to later invade other abdominoperineal organs
Hematogenous: portal circulation to liver; lumbar/vertebral veins to lungs
Lymphogenous: regional LNs
Transperitoneal
Intraluminal
Is CEA useful for colorectal CA?
Not for initial screening but for baseline and recurrence surveillance (but offers no proven survival benefit)
What unique diagnostic test is helpful in pts with rectal CA?
Endorectal u/s (probe is placed transannally and depth of invasion and nodes are evaluated)
How are colorectal tumors staged?
TMN staging system
Explain stage I TMN system?
Invades submucosa or muscularis propria (T1-2, N0, M0)
Explain stage II TMN system
Invades through muscularis propria or surrounding structures but with neg nodes (T3-4, N0, M0)
Explain stage III TMN system?
Positive nodes, no distant metastasis (any T, N1-3, M0)
Explain stage IV TMN system?
Positive distant metastases (any T, any N, M1)
What percentage of pts with colorectal CA have liver metastases on diagnosis?
~20%
What are the common preop IV abx for colorectal CA?
Cefoxitin
Carbapenem
If the pt is allergic (hives, swelling), what abx should be prescribed for colorectal CA?
IV Cipro and Flagyl
What are the tx options for colorectal CA?
Resection: wide surgical resection of lesion and its regional lymphatic drainage
What decides low anterior resection (LAR) vs abdominal perineal resection (APR)?
Distance from the anal verge
Pelvis size
What do all rectal CA operations include?
Total mesorectal excision- remove the rectal mesentery, including the LNs
What is the minimal surgical margin for rectal CA?
2 cm
How many LNs should be resected with a colon CA mass?
12 LNs minimum for staging and may improve prognosis
What is the adjuvant tx of stage III colon CA?
5-FU and leucovorin (or levamisole) chemo (if there is nodal metastasis postop)
What is the adjuvant tx for T3-T4 rectal CA?
Preop radiation therapy and 5-FU chemo as a “radiosensitizer”
What is the MC site of distant (hematogenous) metastasis from colorectal CA?
Liver
What is the tx of liver metastases from colorectal CA?
Resect with greater than or equal to 1 cm margins and administer chemo if feasible
What is the surveillance regimen for colorectal CA?
PE Stool guaiac CBC CEA LFTs (every 3 mos for 3 yrs, then every 6 mos for 2 yrs) CXR for 6 mos every 2 yrs and then yearly Colonscopy at yrs 1 and 3 postop CT scans directed by exam
Why is followup so important the first 3 postop years?
~90% of colorectal occurrences are within 3 yrs of surgery
What are the MC causes of colonic obstruction in the adult population?
Colon CA
Diverticular dz
Colonic volvulus
What is the 5-yr survival rate after liver resection with clean margins for colon CA liver metastasis?
~33% (28-50%)
What is the 5-yr survival rate after dx of unresectable colon CA liver metastasis?
0%
