Cancer that begins in the colon is called colon cancer, and the cancer that begins in the rectum is called rectal cancer. Cancers affecting either of these organs also may be called colorectal cancer. It is a disease which malignant (cancer) cells first form in the tissues of the colon. Colorectal cancer occurs in rectum or the large intestine. This type of cancer occurs when abnormal tissues grow on the inner walls of the colon and rectum. These abnormal tissues commonly present in the form of polyps. Polyps grow as a projection of tissue away from the colon wall, remaining connected to the colon wall of a thin stalk. Their shape is similar that of a mushroom. Polyps are fairly common, especially in older people. The vast majority of polyps are not cancerous. However, some polyps will eventually become cancerous. Unchecked, a cancerous polyp gives rise to a tumor, which grows in size until it penetrates to bowel wall and involves adjacent organs and lymph nodes through the process known as metastasis.
In general, colorectal cancers tend to be slow growing, gradually enlarging and eventually penetrating the bowel wall. When they do spread, it is usually through invasion of nearby lymph nodes. On the right side of the colon near the cecum, cancers usually grow into the space within the colon. They can become large enough to be painful and are likely to cause bleeding. In these cases anemia from chronic blood loss is often the first sign and is why a stool test for occult, or hidden, blood is important.
Most polyps and cancers appear on the left side of the colon. In the left or descending colon, where the channel is narrow, the cancer usually grows around the colon wall and encircles it. Left-sided cancer typically constricts the bowel channel, causing partial blockage.
Symptoms may include:
• Diarrhea, constipation, vomiting, fatigue.
• Going to the toilet more often.
• A feeling that the bowel does not empty properly after a bowel movement.
• Pain and bloating in the abdomen.
• Blood in stools.
• Inexplicable weight loss.
• A lump in the tummy.
• Unexplained iron deficiency in men, or in women after the menopause.
• Age and gender.
• High cholesterol diet.
• Inflammatory Bowel Disease (IBD).
• Lack of exercise.
• Numerous adenomatous polyps develop in the colon, ultimately leading to cancer.
• A family history of this cancer.
• Drug effects.
A person with colorectal cancer will be diagnosed in following ways:
• It is found on a routine screening test.
• Symptoms lead a person to the doctor, and tests to find the cause of the symptoms reveal colorectal cancer.
Treatments may include following options, alone or in combination:
• Surgery – Surgical options include:
1. Bowel resection: This operation involves cutting into the abdomen to reach the area of the colon or rectum that is affected by the cancer. The surgeon cuts out the cancer as well as the parts of the colon or rectum that are next to it. Then the two healthy ends of the colon or rectum are sewn back together.
2. Liver resection: In this operation the surgeon cuts out the cancer that has spread to the liver and also cuts out parts of the liver that are next to the cancer. Up to half of your liver can be removed as long as the rest is healthy. If the cancer in your liver is too large to remove with surgery, you may be given chemotherapy to shrink the tumor. If the tumor becomes small enough, it can be removed with surgery.
3. Lung, adrenal, or ovarian resection, depending on where the cancer has spread.
If the cancer that has returned to the intestine is large, more of the colon or rectum may have to be removed.
• Chemotherapy: –
Chemotherapy may be recommended before surgery in some cases, even if metastatic disease appears confined to the liver. Chemotherapy after surgery can prolong survival for people whose cancer has spread to nearby lymph nodes. The way the chemotherapy is given depends on the type and stage of the cancer being treated. If surgical removal of the liver metastases is successful, additional chemotherapy is usually recommended after surgery.
• Radiation therapy: –
Radiotherapy is not used routinely in this cancer, as it could lead to radiation enteritis, and it is difficult to target specific positions of the colon. It is more common for radiation to be used in rectal cancer, since the rectum does not move as much as the colon and is thus easier to target. If the therapy is given before surgery, radiation may reduce tumor size. This can improve the chances that the tumor will be removed successfully. Radiation before surgery also appears to reduce the risk of the cancer coming back after treatment.
• Targeted therapy: – The therapy is a type of treatment that uses drugs or other substances to identify and attack specific cancer cells without harming normal cells. Monoclonal antibody therapy is a type of targeted therapy used in treatment of it.
• Immunotherapy: This therapy enhances the body's immune system and increases the likelihood that the cancer cells will be killed.
• Monoclonal antibodies: – These antibodies are proteins produced in a laboratory that can identify a cancer cell for destruction or prevent the tumor cell from dividing.
• Gene therapy: – This therapy involves altering genetic material. Either a new gene is introduced to enhance the ability of the body to kill cancer cells or a gene is administrated directly to the cancer cells, causing them to die. Getting the gene to the right cells in the body is a major challenge. The treatment is still experimental and in its early stages of development.
Cancer of the colon and rectum is common. The risk for development of colorectal cancer in patients with ulcerative colitis appears to depend on the duration of disease, the severity of disease, family history of it. Most importantly, patients need to be educated about the risk of developing colorectal cancer. Recent advances have allowed colorectal cancer screening guidelines to be refined. They have also suggested the improvement in quality and application of testing tools. Decreases in both colorectal cancer occurrence and mortality have already occurred and are considered attributable to screening efforts.