Colorectal cancer (CRC)

Diagnostics

The final diagnosis is made based on the medical history, physical exam, and results of laboratory and imaging tests.

Meeting the Amsterdam criteria indicates referral to a genetic counselor and genetic testing.

Check-up plan:

• Examination, palpation of the mammary glands and regional lymph nodes, medical history, family history.
• CBC and urine tests.
• Carcinoembryonic antigen (CEA).
• Testing of the hemostasis system.
• Colonoscopy with biopsy, rigid rectoscopy.
• Pelvis MRI before planning chemo-radiotherapy and preoperative treatment.
• Irrigoscopy or CT colonography if total colonoscopy is not possible.
• Abdominal CT scan with intravenous contrast.
• Osteoscintigraphy — in case of suspected metastatic bone lesions of the skeleton.
• Positron emission tomography.
• External respiration function (ERF) examination.
• Brain MRI with intravenous contrast — if a metastatic brain lesion is suspected.
• Genetic testing for somatic mutations in KRAS, NRAS, BRAF genes, and MSI/dMMR testing in the biopsy/FFPE sample is recommended if distant metastases are present; this may affect the treatment protocol choice. Without a mutation in the RAS, BRAF family genes, additional testing of HER2 expression or amplification is possible.

The endoscopic removal should be performed In all patients with colon polyps without signs of malignancy, if technically possible.

Before removal of polyps larger than 1 cm, a biopsy should be performed and malignancy excluded. The biopsy should be taken both from the surface and from the polyp pedicle area.

In polyps smaller than 5 mm, malignant growth may be present in 1.5–7.7% of patients.

There is a higher probability of malignancy for proximal polyps, as well as for multiple colon polyps. The risk of malignancy is proportional to the size of the polyp.

Follow-up after polypectomy is recommended for all patients.

The frequency of monitoring depends on the number and size of polyps, the presence of established hereditary syndromes.

Bethesda Criteria for MSI (Microsatellite Instability) Testing

1. CRC in a patient diagnosed before age 50.
2. Presence of synchronous, metachronous or other NHPCC-associated (Lynch syndrome-associated) tumors, regardless of age.
3. CRC with high microsatellite instability (MSI-H) in a patient before age 60.
4. CRC in one or more first-degree relatives diagonosed with HNPCC or NHPCC-related tumor before age 50.
5. CRC diagnosed in two or more of first or second degree relatives with HNPCC-related tumor regardless of age.

Amsterdam II criteria for cancer risk assesment and genetic counseling

1. At least 3 relatives have a Lynch syndrome-related cancer (colorectal cancer, endometrial cancer, cancer of the stomach, ovaries, ureter/renal pelvis, brain, small intestine, hepatobiliary tract, and skin (sebaceous glands)) and One is a first-degree relative (parent, brother or sister, or child) of the other 2 relatives.
2. At least 2 successive generations are affected.
3. At least 1 relative had their cancer when they were younger than age 50.
4. Familial adenomatous polyposis is excluded in cases of colorectal cancer.
5. Tumors should be verified whenever possible.

Genetic testing criteria for patients with suspected Lynch syndrome in Russia

1. A patient with colorectal cancer before age 43.
2. Along with colorectal cancer, 2 or more cases of malignant tumors of any localization in a patient or in first degree relatives, regardless of age.