En español | You know you should schedule your colonoscopy, but you might not realize that colon cancer is the third most commonly diagnosed cancer, and the third leading cause of cancer death in both men and women, according to the American Cancer Society. In 2020, there were an estimated 104,610 new cases of colon cancer and 43,340 cases of rectal cancer diagnosed in the United States, and almost 90 percent of those cases were diagnosed in adults age 50 and older. Colorectal cancer, which includes cancer in parts of the large intestine, takes an especially steep toll on African Americans; they are 20 percent more likely than whites to be diagnosed with the disease.
Yet there's some very good news: colorectal cancer death rates have been slowly decreasing year by year. This is due both to increased screening, as well as advances in treatment, says David Liska, M.D., a colorectal surgeon at the Cleveland Clinic. But while death rates have steadily slowed in older adults, “we're most concerned about rising numbers of both cases and deaths among people younger than 50,” Liska notes. That's why the United States Preventive Services Task Force recently revised its recommendations to advise colon cancer screening begin at age 45.
Here's our comprehensive guide to everything you need to know about the disease.
Colorectal cancer defined
Colorectal cancer starts either in your colon or your rectum, both of which are parts of the large intestine. Most of these cancers start out as polyps, or growths on the inner lining of your colon or rectum. “Some types of polyps can turn cancerous, but not all polyps become cancer,” explains Liska.
Ask the expert
Q&A with Scott Kopetz, M.D., professor and deputy chair of GI Medical Oncology at the University of Texas MD Anderson Cancer Center
Why are people getting diagnosed at younger and younger ages with colorectal cancer?
That's a great question, and one we don't really know the answer. We do know it's not driven by genetics, as rates of hereditary colorectal cancer haven't changed. There's some thought that it could be related to increased obesity, but that can't be the answer entirely. One reason may be changes in people's gut microbiomes. The normal, healthy bacteria that helps keep things stable and healthy may be disrupted by environmental exposures like diet. We're watching this carefully, though, and we are also concerned that we may also see the incidence rise among patients in their 50s and 60s in the future.
What's the single most important thing I can do to lower my colorectal cancer risk?
Stay up to date on your screenings. There are certain things that raise your risk substantially, like having a hereditary disease like Lynch syndrome that's linked to colorectal cancer. But the other risk factors are fairly modest. It's not like lung cancer, where we can pinpoint many of the cases back to smoking. True, lifestyle can play a role, but you can be at a healthy weight, eat a good diet, exercise regularly, and avoid smoking and alcohol and still develop colon cancer. Everyone is really at risk for this cancer, which is why preventive screenings like colonoscopies are so important.
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.
Getting a diagnosis
The gold standard of colorectal cancer screening is a colonoscopy. During this procedure, a doctor checks your rectum and colon for polyps (masses of tissue) with a flexible tube while you're sedated. You should have this done every 10 years after the age of 45, or more frequently if you're at higher risk of colorectal cancer or if you have any suspicious symptoms, says Labow.
Unfortunately, only about 66 percent of all adults over the age of 50 are up to date on colorectal screening, according to the American Cancer Society. “These aren't pleasant tests, especially colonoscopies, which require a lot of prep and taking a day off of work,” explains Labow. If you're really squeamish, you can do one of the three at-home stool sample tests: either a fecal occult blood test (FOBT), fecal immunochemical test (FIT) or the stool DNA test (Cologuard). If you do these regularly (either once a year, or, in the case of Cologuard, every three years) research shows they're just as effective at reducing death rates from colorectal cancer as a colonoscopy. Just be prepared to have a colonoscopy if your test reveals anything suspicious, stresses Labow.
Stages of colorectal cancer
Once a colorectal cancer is diagnosed, staging becomes key. “Thankfully, most cases in adults over the age of 50 are caught early, thanks to screening tests like colonoscopies,” says Kopetz.
Stage 1 The cancer has grown into the middle layers of your colon or rectum, but hasn't gone beyond that.
Five-year survival rate: 89 to 91 percent.
Stage 2 The cancer has spread to the outer layer of your colon or rectum but hasn't spread into the lymph nodes.
Five-year survival rate: anywhere between 80 and 90 percent, says Labow.
Stage 3 The cancer has spread into surrounding lymph nodes.
Five-year survival rate: 72 percent.
Stage 4 The cancer has spread to at least one distant organ, like your liver or lungs.
Five-year survival rate: 14 to 16 percent.
What to expect from top treatments
Colorectal cancer treatment typically includes surgery, chemotherapy and, occasionally, radiation, says Liska. Here's what to expect:
Surgery During the surgery, the tumor itself and some surrounding tissues containing lymph nodes are removed and examined to make sure the cancer itself hasn't spread beyond the colon. Most of the time, the two ends of your colon can be reconnected right away. If inflammation in the area prevents this, your surgeon will perform an ostomy, where your colon is temporarily sewn to your abdominal wall. You'll have to wear a bag over the ostomy to collect bowel movements until your colon heals enough to be reconnected again (typically after a few months).
Chemotherapy If you have early-stage disease, where the cancer is only confined to the bowel wall, surgery is often enough. But if your cancer is stage 2 or higher, you will probably require chemotherapy as well. If you have colon cancer, you'll most likely have chemo after surgery. If you have rectal cancer, you'll have both chemo and radiation before and possibly even after, as well.
Even after your cancer has gone into remission, you'll still require frequent follow-up. This usually involves a colonoscopy a year after surgery, then every three to five years. You'll see your cancer team frequently for the first couple years, then taper off to every six months. If your cancer was advanced (stage 2 or beyond) then you'll also get an annual computed tomography (CT) scan for at least three years.
On the horizon: a personalized cancer vaccine
mRNA technology has been making headlines for its use with the COVID-19 vaccines, but it may also play an important role in colon cancer. At MD Anderson, Kopetz is testing the technology in a clinical trial. “We are actually analyzing colon cancer patients’ tumors to look for genetic mutations that could be fueling the cancer's growth,” he explains. Once they're identified, the researchers create a personalized mRNA vaccine. As with the COVID-19 vaccines, the mRNA instructs a patient's cells to produce protein fragments identical to the tumor's genetic mutations. “This hopefully primes the immune system to go after the residual tumor cells and clear them out,” explains Kopetz.
This same technology may also prevent a recurrence of colorectal cancer. “Even after surgery, cancer cells can remain in the body and shed DNA into the bloodstream, otherwise known as circulating tumor DNA (ctDNA),” says Kopetz. But there are now various blood tests available, including Signatera, to check these circulating levels. “If there is ctDNA present, it can mean that a patient is at higher risk for the cancer coming back, and we can adjust their treatment accordingly,” explains Kopetz. “It's a good example of how novel therapies can be combined with novel diagnostics so that we can fight colorectal cancer at an earlier stage than we've ever been able to before."
The following experts provided content for this story:
- David Liska, M.D., a colorectal surgeon at the Cleveland Clinic
- Scott Kopetz, M.D., professor and deputy chair of GI Medical Oncology at the University of Texas MD Anderson Cancer Center
- Daniel Labow, M.D., site chair of surgery for Mount Sinai Morningside and Mount Sinai West in New York City