Colon is the lowest part of the digestive system. It is the another name for large intestine. The colon helps to absorb water and salts from the stools which then passes through the rectum and finally exits through anus. Colon cancer is the malignant growth in the cells of the large intestine. This cancer usually develops from adenomatous polyps. These are small non-cancerous tumors that form on the walls of the large intestine.
Early diagnosis and removal of polyps through colonoscopy prevents from developing into malignant colon cancer. The out of control colon cells can invade the nearby cells resulting in tumors and causing complications as well. Once the malignant tumors form, the cancerous cells may travel to other parts of the body via blood and lymph destroying healthy tissues through out the body.
This stage of the cancer is known as metastasis and is difficult to treat. Usually colon cancer occurs in combination with rectal cancer, a condition referred to as colorectal cancer.
Causes of Colon Cancer
Normally the cells follow a path of growth, division and death. But the cancerous cells do not die, defying the norm and continue to grow and divide. Although scientists do not know the exact reason for this behavior, but they have identified certain causes of colon cancer.
Our large intestine may have several precancerous polyps which may later develop into colon cancer. Polyps are of many types and the most common types are
- Inflammatory polyps – which occur due to the inflammation of the large intestine and later lead to cancer of the colon.
- Adenomas – If not removed during colonoscopy, can lead to cancer.
- Hyperplastic polyps – Rarely lead to cancer of the colon.
- DNA type – Damages or mutations of DNA causes damage to the genes related to cell division. As a result the cells start to grow uncontrollably. Cancer results when gene mutations in the cell cannot correct the cell’s DNA damage and the cell is unable to die. Also mutations inhibit certain gene functions that lead to malignant cell growth resulting in cancer.
- Family Type – Cancer can be hereditary. One can be born with a defective gene or with certain mutations in genes which increases their risk of developing cancer in the later stages.
Several diseases and health conditions can increase the chances of colon cancer. Diabetes, disorder of the growth hormone known as acromegaly, radiation therapy taken for other types of cancers and even Crohn’s disease increases the risk of colon cancer.
With age the risk of getting this type of cancer increases. Around 90% of the diagnosed cases are above the age of 50. People who are obese and have sedentary lifestyle are more likely to get this condition. Diets that are rich in fats and calories but low in fiber increases the chances of colon cancer. Heavy intake of red meat and processed meats can also lead to this cancer. Alcohol consumption and tobacco smoking also increases the risk.
Symptoms of Colon Cancer
Most of the people do not experience any symptoms in the initial stages. But at later stages the symptoms of colon cancer include the following:
- Changes in the consistency of the stools
- Bleeding in the rectum
- Narrow stools
- Continuous urge to defaecate
- Pain or gas in the abdomen
- Pain during the bowel movement
- Sudden weight loss
- Irritable Bowel Syndrome
If the tumor spreads to other body parts known as metastasis, other symptoms related to that particular part may surface. Usually liver is more likely to experience metastasis.
Doctor will do a total body physical exam and checks the person’s medical and family history to diagnose colon cancer. To arrive at a conclusion, colonoscopy is a must. In some cases, doctor may take barium enema X-ray instead of colonoscopy.
For colonoscopy, the doctor inserts a thin tube with a camera into the rectum to inspect the colon. In case polyps are present, the doctor removes them and sends them for biopsy.
For barium enema, patient should not eat or drink several hours before the test. Then the doctor injects a solution containing barium into the colon via rectum. After sometime the barium lines the large intestine, the doctor takes the X-ray of both colon and rectum. In the X-ray, the tumors and polyps if any appear dark against white barium background.
If a biopsy confirms the cancer, the doctor usually recommends ultrasounds, chest X-rays and CT scan of the liver, lungs and abdomen to check for the spread of the tumor.
Colon Cancer Prognosis
After diagnosis, determining the stage of cancer helps in the colon cancer prognosis. Doctors usually follow the TNM system for staging.
- T indicates the size of the tumor and the extent of its invasion.
- N indicates the extent to which the tumor has spread into the lymph nodes
- M indicates the extent of metastasis in other organs of the body.
According to this classification, (T1, N0, M0) can be given for a small tumor that has not spread to either the lymph nodes nor the distant organs. On the basis of the TNM system, we can designate the stages from stage 0 to IV.
For stage 0, it will be (Tis, N0, M0) where Tis indicates insitu tumor. This means the tumor is only in the inner layer of the colon and has not spread either to the outer layers nor invaded the deeper tissues outside the colon.
Accordingly for stage IV, it will be (Any T, Any N, M1). This means the tumor has spread to the distant organs in the body.
Colon Cancer Treatment
As with other cancers, colon cancer treatment depends on the type & stage of the cancer, age, health condition and other personal traits of the person. There is no single reliable treatment. Usually, a combination of treatments is employed. Common colon cancer treatments include the following:
Surgery involves the removal of a part of or the entire colon and is known as colectomy. Colectomy involves the removal of the cancerous part along with the surrounding areas close to the tumor. Depending on the extent of colectomy, colostomy is done latter. For this, the healthy portion of the colon is attached to the stoma of the abdomen or in some cases to the rectum. In the former option, the stools exit via stoma into a colostomy bag instead of through rectum.
Chemotherapy is generally done for the stage of the cancer which has spread to other parts. Chemicals interfere with the cell division process. They either damage the proteins or the DNA leading to the death of the cancerous cells. Normal cells recover from the damage due to chemotherapy but the cancer cells cannot. Side effects include nausea, vomiting, fatigue and hair loss. It works as a standalone treatment or in combination with other treatments.
It is also known as radiotherapy. In this therapy, high energy rays focused on cancer cells destroys them. Damages to the molecules leading to cancerous cells makes them to die in the process. Metals such as radium emit gamma rays. Radiation treatment uses these gamma rays or high energy X-rays. Radiotherapy can act as standalone treatment to shrink a tumor or to destroy the tumor or as a combination with other treatments.
There may be side effects such as sunburn, nausea, vomiting, loss of appetite, diarrhea and trouble in managing weight. But these effects will subside a few weeks after the treatment.