Colorectal cancer, CRC

Notes
  • It is the third most common type of cancer (constituting about 9.7% of all cancer cases).
  • Colon cancer is more common in women while rectal cancer is more common in men.
  • It is one of the most curable cancers, especially with early detection.
  • Statistics: the age that is most affected by CRC- ≥ 40yrs; CRC cases that occur in the rectum and sigmoid - 70%; the prevalence of synchronous CRC (which is a second carcinoma diagnosed less than 6-12 months after the diagnosis of the index tumor) globally - 5%: proportion of CRC that is due to adenocarcinomas - 95%; proportion of CRC that has genetic aetiology-20%; 10-yr survival rates of various stages of CRC after the best care - CRC limited to the mucosa (90%), CRC with extension through the bowel wall (70 to 80%), CRC with positive lymph nodes (30 to 50%) and CRC with metastasis ( < 20%.
  • In the low-resource settings (like Kenya) most patients present at the late stage of the CRC hence the cure rate is low.
  • Risk factors for CRC include;

♦ History of colon or other cancers,

♦ Inflammatory bowel syndrome (IBS),

♦Familial adenomatous polyposis (FAP),

♦Hereditary non-polyposis colorectal cancer,

♦Family history of ovarian, endometrial and breast cancer,

♦Tobacco.

  • CRC spreads by;

♦Hematogenous metastasis

♦Direct extension through the bowel wall

♦Intraluminal metastasis.

♦Perineural spread

♦Reginal lymph node metastasis

  • Staging of CRC;

Stage

(AJCC)

Stage grouping

Stage

Description

0

Tis, N0, M0

♦ Not classified under Duke classification.

Tis – Carcinoma in situ (intraepithelial or invation of lamina propria)

N0 – There is no regional lymph node metastasis.

M0 – No distant metastasis

I

TI, N0, M0

♦ Dukes Stage A tumour

TI – Tumour invades submucosa

T2, N0, M0

♦Dukes Stage BI tumour

T2 -Tumour invades muscularis propria; nodes not involved

II

T3, N0, M0

♦ Dukes Stage B2 tumour

T3-Tumour invades through muscularis propria into subserosa or into noperitonealized pericolic or perirectal tissues

T4, N0, M0

♦ Dukes Stage B2 tumour

T4-Tumour directly (or locally) invades other organs or structures and /or perforates visceral peritoneum.

III

T1, T2

N1 or N2 and M0

♦ Dukes Stage C1 tumour

N1-Metastasis to 1-3 regional lymph nodes

N2-Metastasis to 4 or more regional lymph nodes

T3, T4

N1 or N2 and M0

♦ Dukes Stage C2 tumour

 

IV

Any T,

Any N,

and M1

♦ Dukes Stage D tumour

M1 – Distant metastasis

Symptoms
  • Early CRC is often asymptomatic
  • Non-specific clinical features, especially at early stage of CRC, that include: discomfort, weight loss, change in bowel habits and tiredness.
  • Occult blood
  • Intestinal obstruction
  • Fatigue and weakness (mainly due to anemia)
  • Palpable mass
  • Abdominal pain due to partial obstruction by tumour.
  • Focal pain and tenderness (mainly due to intestinal perforation)
  • Bleeding with defecation (mainly due to rectal cancer)
  • Tenesmus (mainly due to rectal cancer)
  • Hepatomegaly (in case of metastasis)
  • Ascites (in case of metastasis)
  • Supraclavicular lymph node enlargement (in case of metastasis)
Diagnosis
  • Colonoscopy
  • Biopsy for histopathology (usually taken during colonoscopy)
  • Flexible sigmoidoscopy (Test is confirmed by colonoscopy)
  • Fecal occult blood (FOB) testing – (screening recommended annually after age 50 yrs for average-risk patients. Test is confirmed by colonoscopy.
  • CT colonography
  • Double - contrast barium enema x-ray (accuracy less than that of colonoscopy)
  • X-rays, CT scans and Positron emission tomography (PET) to check for metastasis.
  • Measurement of elevated serum carcinoembryonic antigen (CEA) levels, though not suitable for screening due to its low specificity, can be used to monitor the possibility of recurrence of CRC after treatment.
  • Complete blood count (CBC)
Differential
  • Irritable bowel syndrome (IBS)
  • Ulcerative colitis
  • Crohn's disease
  • Haemorrhoids
  • Anal fissure
  • Diverticular disease
Prevention
  • Colorectal cancer screening
  • Avoiding;

_obesity

_tobacco

_physical inactivity

_consumption of  inadequate fruits and vegetables

_alcohol

_Aspirin in a high risk population

 

Management
  • Surgical resection;

♦ Wide resection of the tumor and its regional lymphatic drainage

♦ Operations that entails

_open or laparoscopic segmental resections

_hemicolectomies

_anterior resections as appropriate

♦ Resection of limited liver metastasis

  • Adjuvant chemotherapy;

♦ In resource limited settings (like Kenya), 5-fluorouracil (without or with folinic acid) is used as the mainstay of adjuvant chemotherapy of CRC.

♦ If resources are available oxalipatin is added to 5-fluorouracil/folinic acid.

Other drugs to be considered are;

♦ Capecitabine (a 5-fluorouracil precursor)

♦ Irinotecan

♦ Oxaliplatin.

♦ Monoclonal antibodies

_Bevacizumab

_Cetuximab

  • Adjuvant chemotherapy

♦ Mostly used with adjuvant chemotharapy

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