The role of imaging in the evaluation of colorectal cancer

The article is professionally consulted by Master, Resident Doctor, Specialist I Trinh Le Hong Minh - Department of Diagnostic Imaging - Vinmec Central Park International General Hospital

Colorectal cancer is cancer of the colon or rectum. The disease is usually diagnosed by methods such as endoscopy, endoscopic CT or barium contrast enema. In addition, the doctor may also order the patient to have abdominal and CT scans, PET-CT, pelvic MRI, or endoscopic ultrasound to evaluate the cancer and look for signs of spread.

Colorectal cancer is a type of cancer or malignancy of the large intestine, which can affect the colon or rectum. Factors such as age, race, personal or family history of colon disease as well as diet may play a role in increasing the risk of developing colorectal cancer.
Many colon cancer patients develop over a long period of time, often arising from precancerous colon polyps that gradually grow and can turn cancerous. Most early-stage colon cancers do not show any symptoms. Therefore, different methods of colon cancer screening are now recommended in the hope of finding a polyp or cancer at a time when it can be removed and cured. You should talk to your doctor about when colon cancer screening is appropriate.

If the cancer has grown to the point of causing symptoms, those signs may include:
Abdominal pain, cramps or gas Weight loss Fatigue Changes in bowel movements such as diarrhea, constipation, bloating or very thin stools Blood in the stools or rectal bleeding Partial or complete obstruction of stools/stools

To evaluate colorectal cancer accurately, doctors often order imaging tests such as:
Colonoscopy: This test uses a flexible tube with a small camera at the end, which is inserted through the anus into the colon. The camera records the inside of the large intestine. Polyps or tissue samples can be removed and this also helps with evaluation to determine if they are cancerous. CT scan: A small tube is inserted into the rectum and air is used to inflate the colon. Then, a low-dose CT scan of your abdomen and pelvis is taken when you lie on your back, and then an image of your stomach is taken. CT colonography may be used to measure tumor size. Sometimes a special dye called a contrast medium is used to provide a detailed picture of the condition. This dye can be injected into a patient's vein or taken as a pill or liquid to be swallowed. This test can also detect polyps and tumors. In addition, for patients with colorectal cancer, a CT scan can check for the spread of cancer to the lungs, liver, and other organs. It is usually done before surgery.

Air-contrast barium enema: Also known as low GI (helps with gastrointestinal testing). This test allows radiologists to view images of the colon and rectum in real time and detect abnormal growths. Some other types of imaging tests your doctor may order include:
CT of the abdomen and pelvis: This imaging method uses X-rays to quickly identify the source of pain or abnormalities in the tract Digest. PET/CT: Positron emission tomography (PET) is a type of nuclear medicine scan that uses small amounts of radioactive material to perform bodily functions. The PET/CT test combines images from PET and CT scans to detect and locate cancer and determine how far the cancer has spread. Magnetic resonance imaging (MRI) of the body: This imaging test uses pulses of a magnetic field and radio frequency pulses to create detailed images of internal organs. It can determine the extent of disease if a patient is diagnosed with rectal cancer, consider the stage of the tumor, or evaluate other organs for metastasis.

Endoscopic ultrasound: This imaging test uses high-frequency sound waves generated from a transducer, and inserted into the rectum. The sound waves create an image of the rectal wall and surrounding tissue. Colorectal ultrasound may be used to determine the extent of local disease if a patient is diagnosed with rectal cancer. Biopsy: A colon biopsy is the removal of a small amount of tissue for examination under a microscope. Other tests may suggest that cancer is present, but only a biopsy can definitively diagnose colorectal cancer. A pathologist, after analyzing the sample, interprets laboratory tests and evaluates cells, tissues, and organs to diagnose disease. A biopsy can be done during a laparoscopy, or it can be done on any tissue removed during surgery. Sometimes, a CT scan or ultrasound is used to help perform a biopsy.

Molecular testing of the tumor: Your doctor may recommend that you run laboratory tests on a tumor sample to identify specific genes, proteins, and other factors for the tumor. The results of these tests can help determine the right treatment options for your colorectal cancer. All colorectal cancers should be checked for problems with the mismatch repair protein, known as defect of mismatch repair (dMMR). Because, this test will have two reasons for colorectal cancer. First, it's a way to look for Lynch syndrome. Second, the results will be used to find out whether immunotherapy should be considered in patients with metastatic disease.
Alternatively, this test can be done by special staining of tissue taken from a biopsy or surgery or by performing analyzes that look for changes called microscopic instability ( MSI).
Blood tests: Because colorectal cancer often bleeds into the large intestine or rectum, people with the disease may develop anemia. Performing a test of the red blood cell count in the blood as part of a complete blood count (CBC), which may indicate that bleeding may be present.

In addition, several other blood tests may be used to detect levels of the protein carcinoembryonic antigen (CEA). High levels of CEA may indicate that the cancer has spread to other parts of the body. CEA is not a perfect test for colorectal cancer, because with high CEA levels only about 60% of people with colorectal cancer have metastasized to other organs from the colon. In addition, other medical conditions that are not warranted during testing can also cause CEA to increase. For this reason, the CEA test is often used to monitor colorectal cancer in people who have already been treated. It is not useful as a screening test.

Depending on the size and spread of the cancer, the patient may need to undergo a surgery, removing part or all of the colon, to remove the tumor. For some patients, it may be necessary to remove the bowel or small intestine, which transfers the bowel contents into an external pouch. Alternatively, a combination may require radiation therapy (often in combination with chemotherapy) prior to surgery. This is often referred to as external beam therapy (EBT): This treatment is a form of radiation therapy that is given by aiming several beams of high-energy X-rays directly at your tumor. patients within one to six weeks. These X-rays deliver radiation to the patient's tumor to destroy cancer cells while minimizing impact on surrounding healthy tissue. The most common side effects of this method are fatigue and a change in bowel frequency.
In many cases, chemotherapy can be used as a standalone treatment or in combination with radiation therapy. Chemotherapy is given to help reduce the chance of the tumor coming back elsewhere in the body or to reduce the amount of tumor throughout the body if all of the tumor cannot be surgically removed. It is usually given over time and alternates with periods of no treatment. Side effects of this procedure can be abnormal blood cell counts, fatigue, diarrhea, mouth sores, and a compromised immune system.

Colorectal cancer can have a good prognosis if it is detected and treated early, so screening for early detection of colorectal cancer is very important. When there are risk factors or suspicious symptoms, you should go to hospitals and specialized medical centers for screening to help detect colorectal cancer early.
Vinmec International General Hospital is implementing a Package of Screening and Early Detection of Colorectal Cancer, made by a team of leading doctors and nurses, experienced in the field of colorectal cancer diagnosis and treatment. rectal. In particular, with the support of a system of modern equipment and technology, along with specialized means to diagnose the disease and classify the pre-treatment stages such as: Endoscopy, CT scan, PET-CT scan, MRI, X-ray, histopathological diagnosis, gene-cell testing,... help detect colorectal cancer early even when there are no symptoms.

References: radiologyinfo.org, cancer.org, mayoclinic.org