Colorectal cancer is cancer that starts in the colon or rectum, both parts of the large intestine in the lower part of the body’s digestive system. Colorectal cancer is the fourth most common type of cancer diagnosed in the United States, accounting for 97,000 new cases of colon cancer and 43,000 new cases of rectal cancer annually. As preventative measures such as colonoscopies become more commonly used to detect colorectal cancer in its early stages, deaths from the disease continue to decline.
Colorectal cancer often begins as a growth called a polyp, which may form on the inner wall of the colon or rectum. Some polyps can become cancer over time, but not all polyps do. The chance of a polyp changing into cancer depends on the type of polyp it is. Adenomatous polyps (adenomas) are referred to as “pre-cancerous” because they sometimes change into cancer. Hyperplastic and inflammatory polyps are more common, but typically are not pre-cancerous and do not turn into cancer.
Many people with colon cancer experience no symptoms in the early stages of the disease. When symptoms do appear, they may include: a change in bowel habits, including diarrhea or constipation or a change in the consistency of the stool, lasting longer than four weeks; rectal bleeding or blood in the stool; persistent abdominal discomfort, such as cramps, gas or pain; a feeling that the bowel doesn’t empty completely; unexplained weight loss.
There are many risk factors associated with colorectal cancer, with lifestyle and overall health being the most prominent factors.
- Diabetes: People with diabetes and insulin resistance have an increased risk of colon cancer.
- Obesity: People who are obese have an increased risk of colon cancer and an increased risk of dying of colon cancer when compared with people considered normal weight.
- Smoking: People who smoke may have an increased risk of colon cancer.
- Alcohol: Heavy use of alcohol increases risk.
- Low-fiber, high-fat diet: Colon cancer and rectal cancer may be associated with a diet low in fiber and high in fat and calories.
- A sedentary lifestyle: People who are inactive, are more likely to develop colon cancer. Regular physical activity may reduce risk.
Other risk factors include:
- Older age: The majority of people diagnosed with colon cancer are over the age of 50.
- African-American race: African-Americans have a greater risk of colon cancer than do people of other races.
- A personal history of colorectal cancer or polyps: If adenomatous polyps have already been present, there’s an increased risk of colon cancer in the future.
- Inflammatory intestinal conditions: Chronic inflammatory diseases of the colon, such as ulcerative colitis and Crohn’s disease, can increase risk.
- Family history: There is a higher risk if a parent, sibling or child has had a colon cancer diagnosis. There’s an even greater risk if more than one family member has had the disease.
- Radiation therapy for cancer: Radiation therapy directed at the abdomen to treat previous cancers increases the risk of colon and rectal cancer.
Men and women with an average risk of colon cancer should begin screenings at age 50. But people with an increased risk, such as those with a family history of colon cancer, should consider screening sooner. Colonoscopies are still the best form of screening available, however other options for the right candidate may include imaging test, blood tests or at-home screening kits.
After a colorectal diagnosis, the next step is called staging. The stage of a cancer describes how much cancer is in the body and if it has spread. It helps determine how serious the cancer is and how best to treat it. Staging tests may include imaging procedures such as abdominal, pelvic and chest CT scans, blood test, colonoscopy or a rectal ultrasound. In many cases, the stage of cancer may not be determined until after surgery.
Stage 0 means the cancer is found only in the innermost lining of the colon or rectum.
Stage I means the tumor has grown into the inner wall of the colon or rectum, but has not grown through the wall.
Stage II means the tumor extends more deeply into or through the wall of the colon or rectum. It may have invaded nearby tissue, but cancer cells have not spread to the lymph nodes.
Stage III means the cancer has spread to nearby lymph nodes, but not to other parts of the body.
Stage IV means the cancer has spread to other parts of the body, such as the liver or lungs.
The stage of cancer, along with its location, will determine the best course of treatment. Colon cancer is occasionally treated differently from rectal cancer. For colon cancer, surgery is the common treatment. In fact, in many cases of this disease, the stage may not be determined until after surgery. Many people with colon cancer receive chemotherapy after or along with surgery. Radiation therapy and a colostomy are typically not needed. For rectal cancer, surgery is also the most common treatment, along with chemotherapy. However, patients with rectal cancer may also receive radiation therapy either before surgery to shrink the tumor or after in conjunction with chemo. An estimated 12% of rectal cancer patients, or 1 in 8, will require a permanent colostomy.
Surgical options for colorectal cancer include:
- Colonoscopy: If early staged cancer is localized in the colon or upper rectum and is contained within a polyp, it can be completely removed during a colonoscopy.
- Endoscopic Mucosal Resection: Procedure that removes larger polyps along with a small amount of the lining of the colon or rectum.
- Laparoscopy: Procedure that requires a small incision in the abdominal wall to insert a camera used to help remove cancerous polyps and samples from neighboring lymph nodes.
- Partial Colectomy: Removing the part of the colon that contains the cancer, along with a margin of normal tissue on either side of the cancer. Reconnecting the healthy portions of the colon or rectum can often be done through a minimally invasive approach (laparoscopy).
- Ostomy: When it’s not possible to reconnect the healthy portions of the colon or rectum, a new route needs to be created to expel waste. This procedure creates an opening in the wall of the abdomen (stoma) from a portion of the remaining bowel for the elimination of stool into a bag that fits securely over the opening. Sometimes the ostomy is only temporary, allowing the colon or rectum time to heal after surgery. In some cases, however, the colostomy may be permanent.
In addition to surgery, chemotherapy and/or radiation therapy, some colorectal patients may also be candidates for targeted drug therapy (drugs that target specific cell malfunctions) or immunotherapy (drugs that enlist the body’s own immune system to fight against the cancer).