Colorectal cancer

Not true regarding pathogenesis of colorectal cancer

A. Red meat releases heme groups in the intestine, which enhance the formation of N-nitroso compounds as well as cytotoxic and genotoxic aldehydes by lipoperoxidation
B. Meat cooked at high temperatures produces heterocyclic amines and polycyclic hydrocarbons that are potential carcinogens
C. Tobacco smoking due to the high content in carcinogens such as nicotine
D. Increased levels of visceral adipose tissue (VAT) suppresses metabolic enzymes such as adiponectin or lectin

Most common site of colorectal cancer

A. Rectum (38%), sigmoid (21%), and descending colon (4%)
B. The caecum (35%) and ascending colon (23%)
C. The transverse colon (24%), flexures (12%) and appendix (5%)
D. Rectum (22%), sigmoid (31%), and descending colon (10%)

All are true of colorectal cancer except

A. Approximately one-third of these tumors are in the colon and two-thirds in the rectum
B. Cholecystectomy may marginally increase the risk of right sided colon cancer
C. Colorectal cancer occurs less frequently in the resource-poor world
D. The p53 gene is frequently mutated in carcinomas but not in adenomas

Most common molecular pathway for colorectal cancer

A. Microsatellite instability (MSI)
B. Chromosomal instability (CIN)
C. CpG island methylator phenotype (CIMP)
D. WNT pathway

Preparation for Surgical treatment of colorectal cancer includes all except

A. Mechanical bowel preparation before surgery is essential
B. Anti embolism stockings should be fitted
C. Prophylactic subcutaneous low molecular weight heparin required
D. Intravenous prophylactic antibiotics are given immediately before surgery

Not true regarding surgery for CRC is

A. Carcinoma of the caecum or ascending colon is treated by right hemicolectomy
B. Carcinomas of the transverse colon is most commonly treated by an extended left hemicolectomy.
C. Left hemicolectomy is the operation of choice for descending colon and sigmoid cancers
D. Laparoscopic surgery for colon cancer has been shown equivalent outcomes to open surgery.

In short

2–8% of colorectal cancer cases arise as a result of inherited syndromes.

The two most common hereditary syndromes that predispose for colorectal cancer development are hereditary nonpolyposis colorectal cancer (HNPCC), also known as Lynch syndrome, and familial adenomatous polyposis coli (FAP).

The adenomatous polyps are of great importance because they harbor the potential to become malignant.
Hyperinsulinemia may contribute to colorectal cancerogenesis directly by stimulating colonic cell proliferation and indirectly by increasing the level of insulin-like growth factor 1 (IGF-1).

The fecal occult blood test is the first-choice screening test in primary care. For CRC screening and detection of occult bleeding, high-sensitivity, guaiac-based (HSgFOBT) or immunochemical-based (FIT) tests are recommended

Endoscopy (colonoscopy, sigmoidoscopy and rectoscope) is the basis for a diagnosis of CRC.
Computed tomographic colonography (CTC) – overall sensitivity is comparable to that of colonoscopy but is significantly lower for detecting polyps <8 mm

New techniques such as diffusion-weighted MRI (DW-MRI) or fibroblast activation protein inhibitor–positron emission tomography (FAPI-PET) is prospective due to high specificity and sensitivity, also in the case of extraperitoneal lesions

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