National Colorectal Cancer Awareness Month, observed each year in March, serves as an excellent opportunity to learn more about the third most common cancer, excluding skin cancer, in both men and women in the US. Colorectal cancer is also the second most common cause of cancer deaths in men and women combined.
In the US, approximately 72 percent of colorectal cancers begin in the colon and 28 percent begin in the rectum. The colon is a muscular, 5- to 6-foot long tube that removes water, salt and some nutrients from digesting food and forms stool. The rectum is a 5- to 6-inch chamber that connects the colon to the anus, the opening through which waste exits the body. Stool is stored in the rectum until you’re ready to eliminate it during a bowel movement.
Colorectal cancer occurs when cells lining the colon and rectum grow out of control and form masses called tumors. Almost all colorectal cancers begin as abnormal growths called polyps that form in the colon and rectum and become cancerous over time. Colorectal cancers typically grow slowly, so you may not notice any signs or symptoms until the cancerous tumors become large.
When present, signs of colorectal cancer may include a change in bowel habits, constipation or diarrhea, a feeling that you haven’t emptied your bowel completely following a bowel movement, bleeding from your rectum, blood on or in your stool, abdominal pain and bloating, unexplained weight loss, weakness or fatigue, unexplained anemia, a lump in your belly or rectum, vomiting and feeling full even when it’s been a long time since you’ve eaten.
The exact cause of colorectal cancer is not clear. In most cases, it develops as a result of a combination of environmental and genetic factors. There are certain factors that put you at an increased risk for developing the disease.
Risk factors for colorectal cancer include being older; being male; eating a diet low in fiber and high in red and processed meats, saturated fats and calories; drinking excessively; smoking; getting little physical activity; being overweight or obese; having inflammatory bowel disease (Crohn’s disease or ulcerative colitis); having Type 2 diabetes; having a history of polyps or an inherited polyposis syndrome; and having had breast, ovarian or uterine cancer.
The signs and symptoms of colorectal cancer are common to other disorders as well, so your doctor will likely perform certain tests to help determine if you have cancer or something else. These may include blood tests, digital rectal exam and imaging tests such as ultrasound or MRI.
In 80 percent of cases, the doctor diagnoses colorectal cancer after performing a colonoscopy on patients reporting symptoms. Colonoscopy is the gold standard for diagnosing colorectal cancer because it has a high degree of accuracy. It also enables the doctor to examine the rectum and entire colon.
During a colonoscopy, the doctor inserts a long, thin, flexible tube with a light and camera on it called a colonoscope intoyour anus and up into your rectum and colon. During the test, the doctor can observe and remove most polyps, which are then tested for cancerous cells in a laboratory.
Once colorectal cancer is detected, your doctor will assign a stage based on how far the cancer has spread. The stages of colorectal cancer range from stage 0, or carcinoma in situ, where the cancer is limited to the lining of the colon or rectum, to stage IV, where the cancer has metastasized, or spread, to other organs of the body.
Treatment is based on the stage of the cancer. It typically involves one or a combination of surgery, chemotherapy and radiation therapy. Other treatments may also be recommended. These include radiofrequency ablation, which kills cancer cells using a probe and heat energy; immunotherapy, which energizes your immune system to fight the cancer; and targeted therapy, which uses medications that, unlike chemotherapy, specifically target cancer cells while leaving healthy cells alone.
Treatment is most effective when colorectal cancer is found in its early stages. But often, there are no symptoms during these stages, so screening is crucial for detecting polyps before they become cancerous and for finding cancer early on.
The American Cancer Society recommends that individuals at average risk for developing colorectal cancer begin routine screening at age 45. If you have a personal or family history of colorectal polyps or cancer, or if you have inflammatory bowel disease, you may have to begin screening earlier. Talk with your doctor about the best screening schedule for you based on your personal risk factors.
- Test to look for blood in your stool once a year
- Test to detect altered DNA in your stool every three years
- Flexible sigmoidoscopy, which examines the rectum and lower portion of the colon, every five years
- CT colonography (virtual colonoscopy), which uses cross-sectional x-ray images to search the colon and rectum for polyps, every five years
- Colonoscopy every 10 years
No one test is best for everyone. Each has advantages and disadvantages. Talk with your doctor about the pros and cons of each test, and together you can determine which is best for you based on your risk factors and preferences. But don’t put off screening. Colorectal cancer is a killer!