Colon and Rectal Cancer
The colon is the large intestine, and it’s about five to six feet long. The last eight to 10 inches is called the rectum. Cancer that begins in the upper part of the intestine is called colon cancer, while cancer begins at the end of the large intestine is call rectal cancer. They are also referred to as colorectal cancer. Most of these cancers begin as small, noncancerous clusters of cells, called adenomatous polyps.
Colorectal cancer is the third most common cancer in men and women in the United States, although rates have been declining in the past 20 years. Men have a slighter higher risk of developing these cancers than women.1
Symptoms of Colorectal Cancer
Early colorectal cancers often do not pain or other symptoms. In those that do have symptoms, one early symptom might be rectal bleeding. When tumors grow larger, other symptoms may develop. Many of these relate to bowel habit changes and include:
- Constipation, diarrhea, or bowel incontinence
- Blood in stool or bowel movements, or stools are narrower than usual
- Feeling that bowel movements do not completely empty the bowel
- Constipation or diarrhea
- Unexplained anemia (a shortage of red blood cells)
- Unexplained weight loss
Many health issues can cause these symptoms; they are not a sure sign of cancer. Still, if you have these symptoms, see your doctor for early diagnosis and treatment.
Diagnosis of Colorectal Cancer
Colorectal cancer mostly develops from polyps. Screening with a colonoscopy or a sigmoidoscopy can detect polyps and remove before they become cancerous.
- Colonoscopy: You are sedated and the doctor inserts a long, flexible, slender tube attached to a video camera and monitor into your rectum and up your colon. This lets your doctor see the inside of your entire colon and rectum.
- Sigmoidoscopy: This is similar to a colonoscopy, except the sigmoidscope can only see the last part of the colon before the rectum, which is called the sigmoid colon.
- Your doctor may also order blood tests to see if you have internal bleeding from a tumor or liver enzyme tests to see if cancer has spread to the liver.
Stages of Colorectal Cancer
Your treatment will depend in part of the stage of your cancer. Staging determines how far the main tumor has grown into the wall of the intestine, whether the cancer has spread to lymph nodes, and whether it has metastasized (spread) to other organs in the body. This is called the TNM staging system. In addition, cancer has four stages from 0 to IV.
Here is a brief summary of stages. For a full description, see the American Cancer Society’s website, How is colorectal cancer staged?
Stage 0: The cancer is in the earliest stage. It has not grown beyond the inner layer (mucosa) of the colon or rectum. This stage is also known as carcinoma in situ or intramucosal carcinoma.
Stage I: The cancer has grown through the inner layer of the colon or rectum but has not spread to nearby lymph nodes or other parts of the body.
Stage II (A, B or C): In A, the cancer has grown into the outermost layers of the colon or rectum but has not gone through them. In B, the cancer has grown through the wall of the colon or rectum but has not grown into other nearby tissues or organs. In C, the cancer has grown through the wall of the colon or rectum and into nearby tissues or organs, but has not spread to lymph nodes or distant sites in the body.
Stage IIIA: The cancer has grown through the mucosa into the submucosa and it may also have grown into the muscularis propria. It has spread to 1 to 3 nearby lymph nodes or into areas of fat near the lymph nodes but not the nodes themselves. It has not spread to distant sites.
Or, the cancer has grown through the mucosa into the submucosa. It has spread to 4 to 6 nearby lymph nodes. It has not spread to distant sites.
Stage III (A, B, C): In A, the cancer has grown into the outermost layers of the colon or rectum and has spread to 1 to 3 nearby lymph nodes or into areas of fat near the lymph nodes. In B, the cancer has grown into the muscularis propria or into the outermost layers of the colon or rectum, and has spread to 4 to 6 nearby lymph nodes. In C, the cancer has grown through the mucosa into the submucosa or it may also have grown into the muscularis propria, and has spread to 7 or more nearby lymph nodes. It has not spread to distant sites. Cancer has not spread to distance sites of the body in Stage III.
Stage IV (A and B): In A, the cancer has spread to one distant organ, such as the liver or lung, or set of lymph nodes. In B, the cancer has spread to more than one distant organ or set of lymph nodes, or it has spread to distant parts of the peritoneum (the lining of the abdominal cavity).
Treatments for Colorectal Cancer
After diagnosing and determining the stage of the cancer, your physician will recommend a treatment plan. Treatments include surgery, radiation, chemotherapy and targeted therapy. Your specific treatment plan will be based on your:
- Overall health
- Medical history
- Stage of the disease
- Your preferences
Surgery is often the primary treatment for colon and rectal cancers.
Surgery for Colon Cancer
Open colectomy: This surgery removes part of the colon and nearby lymph nodes through one, larger cut in the abdomen. The procedure is also called a hemicolectomy, partial colectomy or segmental resection. Usually, about one-fourth to one-third of the colon is removed, depending on the location and extent of the cancer. The remaining sections are then sewn together. Typically patients need pain medicine and a liquid diet for just a few days. Sometimes, a patient’s health prevents the two sections of colon from being reattached right away. Then, the surgeon will attach the end of the colon and a plastic bag to a slit in the abdomen skin. Waste will go into the bag attached to the outside of the abdomen. If the top end of the colon goes to the bag, it’s called a colostomy. If the bottom end of the colon connects to the bag, it’s called an ileostomy. Usually, this is temporary. Once the patient is healthier, the surgeon will reattach the two sections of colon inside the body. In rare cases, however, the bag is permanent.
Laparoscopic-assisted colectomy: This is a newer surgery that removes part of the colon and nearby lymph nodes using thin, long instruments inserted through small cuts in the body. The laparoscope has a camera on the end, which lets the surgeon perform the operation guided by a video monitor that shows what’s happening inside the body. Patients may recover faster from this type of surgery and have less pain due to the smaller incisions. It’s more difficult to do than open surgery so it’s important to find a surgeon who is skilled and experienced in laparoscopic colectomy.
Local excision and polypectomy: In very early colon cancer, Stage 0 or Stage 1, polyps and some tumors can be removed during a colonoscopy. No incision is required. Instead the surgeon cuts out the polyps and small tumors with instruments inserted into the rectum and up the colon with a colonoscope.
Surgery for Rectal Cancer
Proctectomy with colo-anal anastomosis: A proctectomy cuts out the entire rectum in order to remove all the lymph nodes near the rectum. The surgeon then reconnects the colon to the anus, a procedure called colo-anal anastomosis. The surgeries are typically required when there are some Stage I, and Stage II or Stage III tumors in the middle or lower third of the rectum. Sometimes patients need a temporary ileostomy, in which the colon empties into a plastic bag outside the body, while the bowel heals. Then the intestines are reconnected and the ileostomy opening is closed.
Abdominoperineal (AP) resection: This procedure lets the surgeon remove the anus and tissues around it—including the sphincter muscle--to get out cancer in the lower third of the rectum. The surgeon makes one incision in the abdomen, and another in the perineal area around the anus. After the anus is removed, patients need a permanent colostomy to collect and remove stool from their bodies.
Local excision and polypectomy: When rectal cancer is in its earliest stages, or still polyps, the surgeon can remove it during a colonoscopy, without making cuts in the abdomen.
Local transanal resection (full thickness resection): Instruments inserted through the anus cut through layers of the rectum to remove cancer and surrounding tissue. This procedure does not require a surgical incision. It’s generally used to remove small Stage I cancers that are not far from the anus.
Low anterior resection: The surgeon removes the section of rectum that has a tumor without affecting the anus. After the colon is reattached to the remaining part of the rectum, patients can have normal bowel movements. This procedure is used for stage I, II or III cancers in the upper third of the rectum.
Pelvic exenteration: This is an extensive surgery that removes the rectum as well as nearby organs such as the bladder, prostate or uterus when cancer has spread. Patients who have a pelvic exenteration need a permanent colostomy to collect and remove stool thereafter. If the bladder is also removed, patients need a urostomy, a pouch attached to the front of the abdomen to collect urine.
Nonsurgical Treatments for Colorectal Cancer
Radiation therapy: High-energy radiation is used to kill cancer cells and shrink tumors. There are two ways to deliver radiation therapy, including external radiation (external beam therapy) and internal radiation (brachytherapy, implant radiation)
Chemotherapy: Drugs that kill fast-growing cancer cells are given by an IV infusion. Because chemotherapy also kills healthy cells, people getting chemotherapy have significant side effects, including hair loss, nausea, and infections. These side effects usually go away once chemotherapy is completed.
Targeted Therapy: Drugs that interfere with a tumor’s ability to grow are given by IV infusion. These drugs work in different ways than chemotherapy. A patient may receive them at the same time as chemotherapy, or later if chemotherapy didn’t work well.
After Treatment for Colorectal Cancer
Patients are usually seen every 3 months for the first 2 years, and then every 6 months for the next 3 years. During this time, patients should have regular physical examinations, and often need regular blood testing for CEA (a blood test that can mark cancer recurrence in some patients). Patients also need regular colonoscopies at 1- to 3-year intervals to find additional polyps or new cancers.