Gen Surg: Colon Cancer

Question 1

Describe adenoma-carcinoma sequence in colon cancer.

Answer 1

Majority of CRCs arise from pre-existing adenomas (takes 5-10 years).
Sequence: hyperproliferation –> adenomatous polyps –> severe dysplasia (precancerous polyp) –> adenocarcinoma –> cancer.

Question 2

Characteristics of adenoma that may it higher risk for cancerous transformation

Answer 2

Tubular adenomas > 1 cm, villous adenoma, adenoma with high grade dysplasia, sessile serrated polyps >1cm or with dysplasia, traditional serrated adenoma, multiple adenomas of any size (>3).

Pedunculated vs sessile: sessile have higher risk. Tubular adenoma 5% risk, tubulovillous adenoma 22% risk, villous adenoma 40% risk.

Incidence of adenoma increases with polyp size.

Hyperplastic polyps have NO RISK for malignant potential.

Question 3

Presentation of colorectal cancer

Answer 3

L sided: constipation, painless bleeding, pencil-like stools.
R sided: silent, mass in R colon, anemia from chronic slow blood loss.

Question 4

Risk factors for colon cancer

Answer 4

PMHx adenomas, 1st degree relative with CRC (esp if <60), longstanding IBD, FamHx of FAP or HNPCC.

Question 5

Screening guidelines for CRC

Answer 5

Low risk (no risk factors): FiT testing for 50-74 yr olds every 2 yrs. If positive, do colonoscopy. Alternatively can do colonoscopy every 10 years.

Risk factors:

FamHx <60 yrs or 2+ fam members: colonoscopy beginning 10 years prior to when youngest family member was diagnosed or by 40 yrs, repeat q5 yrs.

IBD: if pancolitis >8 yrs or L colon involvement for >15 yrs, start doing colonoscopy q1-2 years with multiple biopsies.

FAP: tx with colectomy.

HNPCC: Colonoscopy starting at 10 yrs earlier than youngest relative Dx’d with CRC or 25 yrs. Scope q2 yrs then annually after 40 yrs.

Question 6

TNM staging for colon cancer

Answer 6

Stage 0: CIS
1-2: invasion of BM, enlarging (T staing)
3: nodal involvement N1+
4: spread (typically liver, bone, lung)

Question 7

Blood supply to colon

Answer 7

SMA: gives off ileocolic and R colic for transverse colon. Gives off middle colic which supplies half transverse colon.
IMA: 2nd half of transverse colon to proximal rectum.
Internal iliac artery provides blood supply to rectum.

Question 8

Mgmt approach to CRC

Answer 8

Surgery: for curative or palliative approach (e.g. bowel blockage, bleeding, perforation). Can do hemicolectomies or anterior resection (sigmoid resection).

Chemo: for advanced cancers or if high risk recurrence post-surgically.

Radiation: rectal cancer pre-surgically to reduce recurrence post-sx.

Question 9

Describe Familial Adenomatous Polyposis (FAP)

Answer 9

Autosomal dominant disease due to germline mutation in APC gene.
Typically have >100 adenomatous colorectal polyps.
Polyps develop in 2nd - 3rd decade of life.
CRC occurs in 100% of untreated individuals by 45 yrs.
Screen with genetic counseling and testing of all 1st degree relatives.
Tx with colectomy.

Question 10

Describe attenuated FAP

Answer 10

More than 10-20 adenomas, less than 100.
Occur at older age, 80% CRC risk by 56 y/o.
Suspect in people that have >10 adenomas in their lifetime.
Refer to hereditary cancer program.

Question 11

Describe Hereditary Non-Polyposis CRC (HNPCC)

Answer 11

Amsterdam Criteria:
3+ relatives with Lunch syndrome associated cancer (CRC, endometrial, SB, ureter, renal pelvis), at least 1 first degree relative, 2 successive generations, at least one diagnosed <50 yrs.

Screening: Colonoscopies starting at 10 yrs earlier than diagnosis of youngest diagnosed relative or by 25 yrs. Scope q2 years then annually.