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8 Symptoms of Colorectal Cancer

​Plus, what you need to know about risk factors, treatments and the future of care

spinner image Colonoscopy appointment marked on the calendar during March, which is Colon Cancer Awareness month represented by the blue ribbon
OntheRunPhoto / Getty Images

Colorectal cancer rates are declining among adults 65 and older, but researchers are picking up on a few concerning trends when it comes to the third-leading cause of cancer deaths in the U.S.

new report from the American Cancer Society finds that the proportion of individuals diagnosed with advanced-stage colorectal cancer is on the rise, increasing from 52 percent in the mid-2000s to 60 percent in 2019. What’s more, diagnoses of colorectal cancer in people under 55 has doubled in the last few decades, from 11 percent in 1995 to 20 percent in 2019.

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“We know rates are increasing in young people, but it’s alarming to see how rapidly the whole patient population is shifting younger, despite shrinking numbers in the overall population,” Rebecca Siegel, senior scientific director of surveillance research at the American Cancer Society, said in a statement. “The trend toward more advanced disease in people of all ages is also surprising and should motivate everyone 45 and older to get screened.”

In fact, the U.S. Preventive Services Task Force updated its guidelines in 2021 to say that individuals should get an initial screening for colorectal cancer at age 45, instead of waiting until they’re 50. One reason screening is so important is because colorectal cancer, which is expected to affect 153,020 people in the U.S. in 2023, often doesn’t cause symptoms in the early stages, says Scott Kopetz, M.D., a professor in the Department of Gastrointestinal Medical Oncology, Division of Cancer Medicine, at the University of Texas MD Anderson Cancer Center in Houston. And catching the cancer in its earlier stages can be lifesaving.

“One take-home message is that screening shouldn’t be based on symptoms,” Kopetz stresses. “When you do have symptoms, colorectal cancer tends to be more advanced. That’s why it’s so important to follow screening guidelines.”

That said, the following red flags indicate you should be checked out immediately, even if you’ve recently had cancer screening such as a colonoscopy.

  1. A change in bowel habits (think diarrhea, constipation or narrowing of your stool) that lasts for more than a few days. 
  2. An urge to have a bowel movement that’s not relieved by having one.
  3. Rectal bleeding. “Any bleeding you see, even if it’s just one time, should not be ignored,” says Daniel Labow, M.D., executive vice chair of the Department of Surgery at the Mount Sinai Health System in New York City.
  4. Dark brown or black stool (which can indicate blood).
  5. Cramping or belly pain.
  6. Weakness and fatigue.
  7. Unexplained weight loss. If you have colorectal cancer, your body releases certain hormones into your bloodstream that can lead to weight loss, even if you continue to eat normally, Labow says.
  8. Unexplained anemia. “It could be from losing blood from someplace like your rectum,” Labow says.

Here’s our comprehensive guide to everything you need to know about the disease.

Colorectal cancer defined

Colorectal cancer starts in either 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,” says David Liska, M.D., a colorectal surgeon at the Cleveland Clinic.​

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.​​​​​​​​

Colorectal cancer 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 among 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,” Kopetz says.​​

Race. Colorectal cancer incidence is highest in people who are Alaska Native, American Indian or Black, according to the American Cancer Society’s 2023 report. The racial and ethnic disparities are similar when it comes to deaths from colorectal cancer.


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Sex. Rates are about 33 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,” Labow points out.

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 as 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’s disease or ulcerative colitis, have almost double the risk of developing colorectal cancer compared with 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 that if you become active when you’re older, you can likely lower that percentage.​​

Obesity. Men with obesity have about a 50 percent higher risk of colon cancer and a 25 percent higher risk of rectal cancer compared with those of normal weight. Women with obesity 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 last year 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, Labow says.​​

Unfortunately, 4 in 10 Americans aged 45 and older are not up to date on colorectal cancer screening, according to the American Cancer Society’s latest report. “These aren’t pleasant tests, especially colonoscopies, which require a lot of prep and taking a day off of work,” Labow explains. [See: 10 Ways to Have a Better Colonoscopy.]

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If you’re really squeamish, you can do one of the three at-home stool sample tests: a fecal occult blood test (FOBT), a 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, Labow stresses.​

Patient Perspective: What I Learned from My Cancer Diagnosis

“If there’s one thing I would shout from the rooftops, it’s not to put off your screenings for colon cancer. I had a routine colonoscopy in 2010, which revealed some colon polyps that put me at higher risk for cancer. My doctor removed them and told me to have a follow-up colonoscopy in five years, but I kept putting it off.

Flash forward to March of 2020, when I began experiencing severe abdominal pain and cramping along with nausea. The pain would come and go, but sometimes it got so intense it felt like someone was tightening a belt and squeezing it right around my abdomen. I put off getting checked out for as long as possible, due to fears around COVID-19, but by May the pain was so intense I ended up hospitalized. I had a colonoscopy on May 8, where they discovered a malignant mass. A week later, after surgery at the Cleveland Clinic to remove the tumor, I learned I had stage 3 colon cancer. I had to undergo three months of chemotherapy and an ostomy bag, but my ordeal ended this fall, when I finished treatment and had surgery in October to reconnect my colon. The experience was brutal, but I feel like I dodged a bullet. If I’d let it go for even just a few weeks more, the cancer could have metastasized.

If there’s one thing I want to stress, it’s to not assume you’re invincible. Colon cancer can happen to you. If you’re due (or overdue), schedule your colonoscopy today.”

Dave Evans, a software sales manager in Rocky River, Ohio

What to expect from top treatments​

Colorectal cancer treatment typically includes surgery, chemotherapy and, occasionally, radiation, Liska says. 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 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 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 after as well.

One new trend is to use chemotherapy and radiation to treat localized colorectal cancer and avoid surgery entirely, Kopetz says. This is mainly used for patients with rectal cancer. You’ll then be watched carefully to make sure the cancer doesn’t recur. Another newer option is immunotherapy for a type of colorectal cancer known as microsatellite instability-high (MSI) colorectal cancer. This type of cancer has a lot of genetic mutations inside its tumors that fuel growth. There are two drugs, pembrolizumab and nivolumab, that are approved by the Food and Drug Administration (FDA) to treat MSI colorectal cancer. These are known as immune checkpoint inhibitors, and they work by blocking signals in the tumor that stop your body’s immune system from working. As a result, your immune system is able to ramp up to fight the cancer. ​​

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 of 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​

Messenger ribonucleic (mRNA) technology made 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 says. 

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,” Kopetz explains.​

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],” Kopetz says. 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,” Kopetz explains. “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.”​

spinner image Dr. Scott Kopetz
Courtesy MD Anderson Cancer Center

Ask the expert

Q&A with Scott Kopetz, M.D., professor, Department of Gastrointestinal Medical Oncology, Division of Cancer Medicine, the University of Texas MD Anderson Cancer Center in Houston

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.

Editor’s Note: This story, originally published April 2, 2021, has been updated to reflect new information.  

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