When — and how — should you be screened for colon cancer?
Colon cancer is the second-deadliest form of cancer after lung cancer. If recent messages about colon cancer screening have left you a little confused, that's understandable. In August, the American College of Physicians (ACP) released updated guidance for colon cancer screening that differs from other major organizations, including recommendations from the American Cancer Society (ACS) and the US Preventive Services Task force (USPSTF).
So, what do you need to know?
How does the advice differ?
First, please note that this advice applies only to people at average risk without a family history of colon cancer. If you have family history, or if other health issues put you at higher-than-average risk for colorectal cancer, talk to your doctor about the best course of action for you.
The main point of disagreement relates to the age at which people should start getting screened. The new ACP guidance says 50, while the other two organizations recommend 45. That earlier age is endorsed by the U.S. Multisociety Task Force on Colorectal Cancer. It's also endorsed by many physicians, including Harvard Medical School professor Dr. Andrew T. Chan, a gastroenterologist and director of epidemiology at Massachusetts General Hospital Cancer Center, who helps explain key facts below.
Why do experts suggest starting screening earlier?
"We're facing an unexplained and alarming increase in the incidence of colon cancer in people younger than 50," says Dr. Chan.
Overall, deaths from colon cancer dropped by 2% per year from 2011 to 2020. But that's not the case among people younger than 50. In that age group, deaths from colon cancer rose between 0.5% and 3% during the same time period, according to statistics published in 2023.
The rising rates of colon cancer in younger people are occurring in all racial and ethnic groups, with the steepest rises seen among Alaskan Natives and Native Americans. Overall, Blacks and African Americans are more likely to get and die from colon cancer than whites, and early-onset cases are higher in Black individuals than whites.
Efforts to encourage colon cancer screening began in the mid-1990s. Today, about 60% of adults over 50 follow the advice to receive a colonoscopy (described below) on a regular basis. This track record, while not perfect, likely explains the decline in deaths from colon cancer in older adults.
"I think that promoting earlier screening will help stem the rise in early-onset cases, at least for those in their 40s. We've also seen that earlier colonoscopies may be associated with lowering incidence of colon cancer even later in life, "says Dr. Chan.
What are the different screening tests for colon cancer?
The two most widely used screening tests are a standard colonoscopy and various stool-based tests.
Colonoscopy. For this test, a gastroenterologist or surgeon snakes a long, flexible tube with a camera on the end through your rectum and beyond to inspect the entire length of your colon. Considered the gold-standard test, this procedure can detect precancerous polyps called adenomas, and allow for their removal.
The test requires taking laxatives and drinking lots of fluids beforehand to clean all the fecal material (stool) out of your colon. Serious complications, which include perforation or bleeding, are rare, occurring in about three in 1,000 procedures. If no polyps are found, a repeat colonoscopy isn't recommended for another 10 years. If you have polyps, or your risk or symptoms change, this interval will be shorter.
Stool tests. The more worrisome colon polyps (adenomas) often shed tiny amounts of blood and abnormal DNA into the stool. This can be detected from samples you collect yourself at home.
- Two tests, the fecal occult blood test (FOBT) and fecal immunochemical test (FIT), check for blood. They require small stool samples that you put on a card or in a tube that's then mailed to a lab. These tests should be done every year.
- A third option, the FIT-DNA test, checks for both blood and abnormal DNA; it's usually repeated every three years.
Additionally, the guidelines from the American College of Physicians suggest another option: flexible sigmoidoscopy, which inspects only the lower part of the colon, once every 10 years, combined with a fecal FIT testing every two years. However, doctors in the United States rarely order sigmoidoscopy today.
If flexible sigmoidoscopy or any of these stool tests show evidence of a problem, a colonoscopy is needed to check for adenomas or cancer.
Why might stool-based screening make sense for younger adults?
Colonoscopy isn't necessarily the best initial screening test for everyone, says Dr. Chan. That's especially true for younger people, mainly because it's time-consuming and inconvenient.
"Maybe you just can't find time in your schedule or are worried about having a colonoscopy," he says. If that's the case, a stool-based test — which is noninvasive and takes very little time — is an appropriate option.
"The worst option is not doing anything, because early detection and treatment can prevent deaths," he says.
About the Author
Julie Corliss, Executive Editor, Harvard Heart Letter
Julie Corliss is the executive editor of the Harvard Heart Letter. Before working at Harvard, she was a medical writer and editor at HealthNews, a consumer newsletter affiliated with The New England Journal of Medicine. She … See Full Bio View all posts by Julie Corliss
About the Reviewer
Howard E. LeWine, MD, Chief Medical Editor, Harvard Health Publishing
Dr. Howard LeWine is a practicing internist at Brigham and Women’s Hospital in Boston, Chief Medical Editor at Harvard Health Publishing, and editor in chief of Harvard Men’s Health Watch. See Full Bio View all posts by Howard E. LeWine, MD
Tick season is expanding: Protect yourself against Lyme disease
In parts of the United States and Canada, warming temperatures driven by climate change may be contributing to a rise in tick-borne illnesses. Ticks are now thriving in a wider geographic range, and appearing earlier and sticking around later in the shoulder seasons of spring and fall. That means we need to stay vigilant about protecting ourselves against ticks that cause Lyme disease and other illnesses — even during winter months in many warmer states and provinces.
Here’s a timely reminder about why preventing Lyme disease is important, and a refresher on steps you can take to avoid tick bites.
What are the symptoms of Lyme disease?
Lyme disease is best known for its classic symptom, a bull’s-eye red rash that appears after a bite from an infected tick (scroll down to see photos of classic and non-classic rashes). However, 20% to 30% of people do not develop a rash. And a rash can be easy to miss because ticks tend to bite in dark body folds such as the groin, armpit, behind the ears, or on the scalp. Some people have flulike symptoms such as a headache, fever, chills, fatigue, and aching joints. So if you notice a rash or have these symptoms, call your doctor for advice. At this stage, prompt antibiotic treatment can wipe out the bacterial infection.
When people don’t receive treatment because they didn’t see the rash or didn’t have other early symptoms, the bacteria can spread to different parts of the body. Not only can the bacteria itself cause problems, but the body’s immune system can over-respond to the infection. Either process, or sometimes both, may harm joints, the heart, and/or the nervous system. And some people treated for any stage of Lyme disease develop post-Lyme disease syndrome, which can cause a range of debilitating symptoms that include fatigue, brain fog, and depression.
How to avoid getting Lyme disease
Preventing tick bites is the best way to avoid Lyme disease and other tick-borne illnesses. Blacklegged ticks (also called deer ticks) may be infected with the bacteria that causes Lyme disease. If you live in one of the areas where the incidence of Lyme disease is high, these steps can help.
Know where ticks are likely lurking. Ticks usually crawl up from leaves or blades of grass on the ground to the legs. So be extra careful when walking through fields or meadows and on hikes where you may brush up against bushes, leaves, or trees. Try to walk on well-cleared paths.
Wear protective clothing. Long pants tucked into socks is the best way to keep ticks from crawling up under the pant leg. Lighter-colored clothing can make ticks easier to see.
Use repellents. You can buy clothing that’s pretreated with the insecticide permethrin (which repels ticks). Or you can spray your own clothes and shoes; just be sure to follow the directions carefully. On all exposed skin, use a product that contains DEET, picaridin, oil of lemon eucalyptus (OLE), IR3535, para-menthane-diol (PMD), or 2-undecanone. This search tool from the EPA can help you find a product best suited for your needs. Pay attention to the concentration of active ingredients: for example, at least 20% but not more than 50% with DEET; between 5% to 20% with picaridin; and 10% to 30% with oil of lemon eucalyptus. Many products come in pump spray bottles or as sticks or wipes, which may make them easier to apply where needed.
Get a tick check. After spending time in tick-infested areas, ask a partner to check you for ticks in areas on your body that you can’t see very well. The common bite areas are the back of the knee, the groin, under the arms, under the breasts in women, behind the ears, and at the back of the neck. The tick species that transmits Lyme disease is about the size of a sesame seed. Note that a tick has to be attached to your skin for 24 to 36 hours for it to transmit enough bacteria to give you the disease.
For more information about preventing Lyme disease or living with it, visit the Harvard Health Publishing Lyme Wellness Initiative.
About the Author
Julie Corliss, Executive Editor, Harvard Heart Letter
Julie Corliss is the executive editor of the Harvard Heart Letter. Before working at Harvard, she was a medical writer and editor at HealthNews, a consumer newsletter affiliated with The New England Journal of Medicine. She … See Full Bio View all posts by Julie Corliss
About the Reviewer
Howard E. LeWine, MD, Chief Medical Editor, Harvard Health Publishing
Dr. Howard LeWine is a practicing internist at Brigham and Women’s Hospital in Boston, Chief Medical Editor at Harvard Health Publishing, and editor in chief of Harvard Men’s Health Watch. See Full Bio View all posts by Howard E. LeWine, MD