Colon Cancer

Colon cancer is a malignancy that begins in the colon, or in the large intestine. The large intestine is an organ which is a long, tube-shaped structure located near the rear end of the digestive system. The colon plays an important role in digestion, since it is responsible for the extraction of some key fluids and nutrients from all consumed food. The colon is also an important unit in the process of excreting solid waste from the human body, via the rectum.


Colonic cancers can come with anemia due to slow loss of blood or with obstruction to bowel. However, these symptoms occur only when the disease is infiltrated locally. Screening methods are available that can detect colonic and rectal cancer before symptoms appear (stage 0). When detected early, these cases can be cured with much simpler surgery.

Symptom of colon cancer depends on the location of the tumor in the colon (ascending colon, transverse colon, descending colon and sigmoid colon).

  • Change in bowel habits like diarrhea, constipation, or feeling that the bowel does not empty completely
  • Bright red or very dark blood in the stool
  • Narrow stools
  • Vomiting, gas pains, bloating, fullness, and cramps
  • Unexplained weight loss
  • Chronic fatigue
  • Anemia

People with any of the above symptoms should seek medical help. Stool occult blood test detects small amounts of blood in stool which may indicate colonic cancer. Colonic cancer is diagnosed by colonoscopy. A biopsy is performed during these procedures to prove the diagnosis.

How Colon Cancer is Diagnosed?

Doctors use different tests to diagnose cancer and some of these tests may include imaging tests and blood tests. These kinds of tests are also done to find out if the cancer has spread from where it had started. For diagnosing a type of cancer there are various factors that are looked into like, the suspected cancer, the patients signs and symptoms, the patient’s health and medical condition, medical and family history and lastly, results from previous medical tests.

In addition to a physical exam, the following tests may be done to diagnose colon cancer.


A colonoscopy is done when a patient is sedated. It allows the doctor to look into the patients colon and also to take a sample of tissue for the confirmation of cancer.

Molecular testing of the tumor

Laboratory tests are run on the tumor sample to check for specific genes, proteins and any other factor that might be unique to the tumor.


A biopsy is the removal of a small amount of tissue that is then examined under a microscope. A biopsy can also be seen as a definite diagnosis to see if colon cancer is present. A biopsy can be done during a surgery or colonoscopy. A CT scan or ultrasound is used to perform a needle biopsy.

Blood tests

A blood test to check for the complete blood count of a person is done to check for anemia. If a person has anemia, which is low red blood cell count, it means the tumor has been bleeding for a long time.

Computed Tomography (CT) scan

A CT scan can be used to check if colon cancer has spread to the liver. In a CT scan, X-rays are used to make detailed cross sectional images of organs.


Sometimes pet-ct scan is needed to look for any distant spread from the colon cancer. Radionuclide material is used in this scan.


It is blood investigation helps in detecting and monitoring for recurrence in colon cancer. It is tumor marker. However, not all colonic cancer patients may not have raised serum CEA values. In smokers also it is slightly elevated compared to non smokers.

Gene tests

Gene tests are often conducted to check to check for specific gene changes in cancer cells. This test is usually done to check how treatment might affect these cells in cases where the cancer has spread. Colon cancer cells are typically tested to check for high levels of gene changes called microsatellite instability (MSI). Testing is also done to check if the cancer cells show changes in any of the mismatch repair genes (MLH1, MSH2, MSH6 and PMS2)

Surgery for colon cancer

This is the most common treatment for colon cancer and is called a surgical resection. In this procedure along with the affected part, part of the healthy colon or rectum and lymph nodes will be removed. Read more about Colon cancer surgery here.

Surgery is Done by Either of the Three Methods

  1. open method
  2. laparoscopic method
  3. robotic method

Other than a surgical resection, there are many other treatment options for colon cancer and they include:

  • Chemotherapy for colon cancer
  • Targeted therapy
  • Anti-angiogenesis therapy
  • Epidermal growth factor receptor (EGFR) inhibitors
  • Checkpoint Inhibitors
  • Radiation therapy for colon cancer
  • Radiofrequency ablation (RFA) or cryoablation

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