If cancer forms in a polyp, it grows into the wall of the colon or rectum. It starts in the inner layers (known as the mucosa), then grows outward through all the other layers. Eventually, it can grow into blood or lymph vessels, where it can travel to lymph nodes and finally spread to distant parts of your body.
Oftentimes, colorectal cancer doesn’t cause symptoms until it’s in the advanced stages, says Scott Kopetz, M.D., professor and deputy chair of GI Medical Oncology at the University of Texas MD Anderson Cancer Center. The following red flags indicate you should be checked out immediately, even if you’ve recently had cancer screening such as a colonoscopy.
- A change in bowel habits (think diarrhea, constipation or narrowing of your stool) that lasts for more than a few days
- An urge to have a BM that’s not relieved by having one
- Rectal bleeding with bright red blood
- Dark brown or black stool (which can indicate blood)
- Cramping or belly pain
- Weakness and fatigue
- Unexplained weight loss
Risk factors to know
Age The vast majority of cases of colorectal cancer still occur in people age 50 or older. Why it’s also increasing in those under 50 isn’t yet known. “One theory is that it’s due to changes in the microbiome, the bacteria in your gut that keep it healthy,” says Kopetz.
Race Not only are African Americans more likely to be diagnosed with colorectal cancer than whites, they are nearly 40 percent more likely to die from the disease, according to the American Cancer Society. Their greater risk comes from lifestyle-related factors such as obesity, as well as lack of access to screening, notes Daniel Labow, M.D., Site Chair of Surgery for Mount Sinai Morningside and Mount Sinai West in New York City.
Sex Rates are about 30 percent higher in men than in women. Female sex hormones may offer some protection, and women are also less likely to smoke. “In general, women tend to take better care of themselves,” points out Labow.
Genetics Almost 30 percent of colorectal cancer patients have a family history of the disease. If you have a first-degree relative — defined as a parent, sibling or child — with colorectal cancer, you have up to four times the risk of developing it has someone without any family history. About 10 percent of the time, that’s due to a hereditary condition such as Lynch syndrome or familial adenomatous polyposis. If any of these diseases run in your family, you can undergo genetic testing to see if you have the cancer-causing gene mutation.
Inflammatory bowel disease People with chronic inflammatory bowel diseases, such as Crohn disease or ulcerative colitis, have almost double the risk of developing colorectal cancer compared to those without these diseases. There’s some preliminary evidence that some of the anti-inflammatory drugs used to treat ulcerative colitis may also lower your cancer risk.
Certain lifestyle factors seem to increase your risk. These include:
Inactivity People who are the most sedentary have up to a 50 percent increased risk of colon cancer. The good news is, if you become active when you’re older, you can likely lower that percentage.
Obesity Obese men have about a 50 percent higher risk of colon cancer and a 25 percent higher risk of rectal cancer compared to those of normal weight. Obese women have about a 10 percent increased risk of colon cancer. Abdominal fat seems especially dangerous.
Diet An eating pattern rich in fiber and calcium, and low in alcohol and red meat, appears to lower risk of colorectal cancer, according to a review of studies published this past February in JAMA Network Open.