Colorectal cancer (also known as colon cancer, rectal cancer or bowel cancer) is the development of cancer in the colon or rectum (parts of the large intestine). It is due to the abnormal growth of cells that have the ability to invade or spread to other parts of the body. Signs and symptoms may include blood in the stool, a change in bowel movements, weight loss, and feeling tired all the time.
Risk factors for colorectal cancer include lifestyle, older age, and inherited genetic disorders. Other risk factors include diet, smoking, alcohol, lack of physical activity, family history of colon cancer and colon polyps, presence of colon polyps, race, exposure to radiation, and even other diseases such as diabetes and obesity. Genetic disorders only occur in a small fraction of the population. A diet high in red, processed meat, while low in fiber increases the risk of colorectal cancer. Other diseases such as inflammatory bowel disease, which includes Crohn’s disease and ulcerative colitis, can increase the risk of colorectal cancer. Some of the inherited genetic disorders that can cause colorectal cancer include familial adenomatous polyposis and hereditary non-polyposis colon cancer; however, these represent less than 5% of cases. It typically starts as a benign tumor, often in the form of a polyp, which over time becomes cancerous.
Treatments used for colorectal cancer may include some combination of surgery, radiation therapy, chemotherapy and targeted therapy. Cancers that are confined within the wall of the colon may be curable with surgery while cancer that has spread widely are usually not curable, with management focusing on improving quality of life and symptoms. .
Types of Colorectal Cancer
Adenocarcinoma is the most common type of colorectal cancer. Other colorectal cancers include gastrointestinal carcinoid tumors, gastrointestinal stromal tumors, primary colorectal lymphoma, Leiomyosarcoma, melanoma and squamous cell carcinoma.
A cancer of the intestinal gland cells, adenocarcinoma represent more than 95 percent of colon and rectal cancers. “Adeno” is the prefix for gland, and adenocarcinoma typically starts within the intestinal gland cells that line the inside of the colon and/or rectum. They tend to start in the inner layer and then spread deeper in other layers. There are two main sub-types of adenocarcinoma:
Mucinous adenocarcinoma is made up of approximately 60 percent mucus. The mucus can cause cancer cells to spread faster and become more aggressive than typical adenocarcinoma. Mucinous adenocarcinomas account for 10 to 15 percent of all colon and rectal adenocarcinoma.
Signet ring cell adenocarcinoma accounts for less than one percent of adenocarcinoma. Named for its appearance under a microscope, signet ring cell adenocarcinoma is typically aggressive and may be more difficult to treat.
Other types of Colorectal Cancer
There are many other types of rare colorectal cancers, and combined these types account for just 5 percent of all cases. Below are examples of other colorectal types:
Gastrointestinal carcinoid tumors: This slow-growing cancer forms in the neuroendocrine cell (a nerve cell that also creates hormones) in the lining of the gastrointestinal tract. These tumors account for just 1 percent of all colorectal cancers, but half of all of the cancers found in the small intestine.
Primary Colorectal lymphomas: A type of non-Hodgkin lymphoma (NHL), lymphomas are cancers that develop in the lymphatic system from cells called lymphocytes. Lymphocytes are a type of white blood cell that helps the body fight infections. NHL can develop in many parts of the body, including the lymph nodes, bone marrow, spleen, thymus and the digestive tract. Primary colorectal lymphomas account for just 0.5 percent of all colorectal cancers, and about 5 percent of all lymphomas. The disease usually occurs later in life, and is more common in men than women.
Gastrointestinal stromal tumors: Also known as GISTs, this is a rare type of colorectal cancer that starts in a special cell found in the lining of the gastrointestinal (GI) tract called interstitial cells of Cajal (ICCs). More than 50 percent of GISTs start in the stomach. While most of the others start in the small intestine, the rectum is the third most common location. GISTs are classified as sarcomas, cancers that begin in the connective tissues, which include fat, muscle, blood vessels, deep skin tissues, nerves, bones and cartilage.
Leiomyosarcomas: Another form of sarcoma, leiomyosarcomas essentially means “cancer of smooth muscle.” The colon and rectum have three layers of the type of muscle that can be affected, which all work together to guide waste through the digestive tract. This rare type of colorectal cancer accounts for about 0.1 percent of all colorectal cases.
Melanomas: Though most commonly associated with the skin, melanomas can occur anywhere, including the colon or rectum.
Squamous cell carcinomas: Some parts of the GI tract, like the upper part of the esophagus and the end of the anus, are lined with flat cells called squamous cells. These are the same type of cells that are found on the surface of the skin. Cancers starting in these cells are called squamous cell carcinoma.
Stages of Colorectal Cancer
Stage 0 : Since these cancers have not grown beyond the inner lining of the colon, surgery to take out the cancer is all that is needed. This may be done in most cases by polypectomy (removing the polyp) or local excision through a colonoscope. Colon resection (colectomy) may occasionally be needed if a tumor is too big to be removed by local excision.
Stage I: These cancers have grown through several layers of the colon, but they have not spread outside the colon wall itself (or into the nearby lymph nodes). Stage I includes cancers that were part of a polyp. If the polyp is removed completely, with no cancer cells in the edges (margins), no other treatment may be needed. If the cancer in the polyp was high grade (see “How is colorectal cancer staged?”) or there were cancer cells at the edges of the polyp, more surgery may be advised. You may also be advised to have more surgery if the polyp couldn’t be removed completely or if it had to be removed in many pieces, making it hard to see if cancer cells were at the edges.
For cancers not in a polyp, partial colectomy ─ surgery to remove the section of colon that has cancer and nearby lymph nodes ─ is the standard treatment. You do not need any additional therapy.
Stage II: Many of these cancers have grown through the wall of the colon and they may extend into nearby tissue. They have not yet spread to the lymph nodes.
Surgery to remove the section of the colon containing the cancer along with nearby lymph nodes (partial colectomy) may be the only treatment needed. But your doctor may recommend chemotherapy (chemo) after surgery (adjuvant chemo) if your cancer has a higher risk of coming back because of certain factors, such as:
- The cancer looks very abnormal (is high grade) when viewed under a microscope.
- The cancer has grown into nearby organs.
- The surgeon did not remove at least 12 lymph nodes.
- Cancer was found in or near the margin (edge) of the surgical specimen, meaning that some cancer may have been left behind.
- The cancer had blocked off (obstructed) the colon.
- The cancer caused a perforation (hole) in the wall of the colon.
- The main options for chemo for this stage include 5-FU and leucovorin (alone) or capecitabine, but other combinations may also be used.
If your surgeon is not sure all of the cancer was removed because it was growing into other tissues, he or she may advise radiation therapy to try to kill any remaining cancer cells. Radiation therapy can be given to the area of your abdomen where the cancer was growing.
Stage III: In this stage, the cancer has spread to nearby lymph nodes, but it has not yet spread to other parts of the body.
Surgery to remove the section of the colon containing the cancer along with nearby lymph nodes (partial colectomy) followed by adjuvant chemo is the standard treatment for this stage. Either the FOLFOX (5-FU, leucovorin, and oxaliplatin) or CapeOx (capecitabine and oxaliplatin) regimens are used most often, but some patients may get 5-FU with leucovorin or capecitabine alone based on their age and health needs.
People who aren’t healthy enough for surgery, radiation therapy and/or chemo may be options.
Stage IV: The cancer has spread from the colon to distant organs and tissues.
Colorectal/Colon Cancer Specialist/Doctor/Consultant in Noida and the Colon Cancer most often spreads to the liver, but it can also spread to other places such as the lungs, peritoneum (the lining of the abdominal cavity), or distant lymph nodes.
Prevention of Colorectal Cancer
Surgery is the mainstay of treatment and involves in block removal of diseased segment with adequate margins, surrounding tissue and lymph nodes. The names given to such resections are right hemicolectomy, transverse colectomy, left hemicolectomy, sigmoid colectomy, and subtotal colectomy.
- Polypectomy:If the cancer is found in a polyp (a small piece of bulging tissue), the polyp is often removed during a colonoscopy.
- Local excision:If the cancer is found on the inside surface of the rectum and has not spread into the wall of the rectum, the cancer and a small amount of surrounding healthy tissue is removed.
- Resection:If the cancer has spread into the wall of the rectum, the section of the rectum with cancer and nearby healthy tissue is removed. Sometimes the tissue between the rectum and the abdominal wall is also removed. The lymph nodes near the rectum are removed and checked under a microscope for signs of cancer.
- Pelvic exenteration:If the cancer has spread to other organs near the rectum, the lower colon, rectum, and bladder are removed. In women, the cervix, vagina, ovaries, and nearby lymph nodes may be removed. In men, the prostate may be removed. Artificial openings (stoma) are made for urine and stool to flow from the body to a collection bag.
Radiation therapy or chemotherapy may be given before surgery to shrink the tumor, make it easier to remove the cancer, and lessen problems with bowel control after surgery. Treatment given before surgery is called neoadjuvant therapy. Even if all the cancer that can be seen at the time of the operation is removed, some patients may be given radiation therapy or chemotherapy after surgery to kill any cancer cells that are left. Treatment given after the surgery, to lower the risk that the cancer will come back, is called adjuvant therapy.
Radiation therapy is a cancer treatment that uses high-energy beams or other types of radiation to kill cancer cells. There are two types of radiation therapy. External radiation therapy uses linear accelerators outside the body to send radiation toward the cancer. Internal radiation therapy (Brachytherapy) uses a radioactive substance sealed in needles, seeds, wires, or catheters that are placed directly into or near the cancer. The way the radiation therapy is given depends on the type and stage of the cancer being treated.
Chemotherapy is a cancer treatment that uses drugs to stop the growth of cancer cells, either by killing the cells or by stopping the cells from dividing. When chemotherapy is taken by mouth or injected into a vein or muscle, the drugs enter the bloodstream and can reach cancer cells throughout the body (systemic chemotherapy). When chemotherapy is placed directly in the cerebrospinal fluid, an organ, or a body cavity such as the abdomen, the drugs mainly affect cancer cells in those areas (regional chemotherapy). The way the chemotherapy is given depends on the type and stage of the cancer being treated.
Targeted 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 being studied in the treatment of rectal cancer.
Monoclonal antibody therapy uses antibodies made in the laboratory from a single type of immune system cell. These antibodies can identify substances on cancer cells or normal substances that may help cancer cells grow. The antibodies attach to the substances and kill the cancer cells, block their growth, or keep them from spreading. Monoclonal antibodies are given by infusion. They may be used alone or to carry drugs, toxins, or radioactive material directly to cancer cells.