Colorectal Cancer: What Millennials and Gen Zers Need to Know

[Originally published: Jan. 29, 2020. Updated: Jan. 17, 2024]

Nobody in their 20s, 30s or 40s gets colorectal cancer, right? Wrong. The truth is that colorectal cancer is on the rise in young adults and has been for years. That’s why Yale Medicine surgeons who treat it are urging people younger than 45—even college students—to talk to their doctors about any suspicious symptoms, such as constipation, rectal bleeding, or sudden changes in bowel movements.

Yale Medicine Colon & Rectal Surgery doctors report seeing young patients with a diagnosis of colorectal cancer more often. They diagnosed colon cancer in a father of four in his 30s who thought for months that his rectal bleeding was caused by hemorrhoids. There was one week when all of the seven patients the practice saw who were diagnosed with rectal cancer were young; the oldest was 35. The youngest colorectal cancer patient diagnosed at this location in recent months was 18.

In early 2023, the American Cancer Society (ACS) reported that 20% of diagnoses in 2019 were in patients under age 55, which is about double the rate in 1995, and rates of advanced disease increased by about 3% annually in people younger than 50. It predicted that, in 2023, an estimated 19,550 diagnoses and 3,750 deaths would be in people younger than 50. In 2021, both the U.S. Preventive Services Task Force (USPSTF) and the U.S. Multisociety Task Force on Colorectal Cancer, two groups that provide preventive guidelines, recommended that most Americans be screened for colorectal cancer at age 45—five years earlier than previously recommended—and continue with screenings periodically until age 75.

“We are seeing a clear uptick in colorectal cancer in younger generations,” says Haddon Pantel, MD, a Yale Medicine colorectal surgeon.

At the same time, while colorectal cancer is still most frequently diagnosed in people over 65, incidence in that group is declining, and older people are less likely than people younger than 50 to be diagnosed with advanced disease.

In fact, according to a 2024 report from the ACS, colorectal cancer has moved up from being the fourth leading cause of cancer death in both men and women under age 50 two decades ago to first in men and second in women. (Breast cancer is the leading cause of death in women under 50.)

Even though colorectal cancer is often highly treatable, the diagnosis can be a major ordeal for Generation Zers, Millennials, and Generation Xers, who range in age from their mid-20s to their late 50s. It can interrupt careers and damage personal finances. Young people diagnosed with colorectal cancer may need to make quick, critical decisions about such matters as preserving sperm or eggs in case treatment impacts their fertility.

About 15 years ago, Yale Medicine surgeon Vikram Reddy, MD, PhD, conducted one of the first studies identifying the rising incidence of colorectal cancer among young people. “We’re still seeing the trend, so it wasn’t temporary,” says Dr. Reddy.

Dr. Reddy and his colleagues are passionate about educating people so the cancers will be diagnosed early, when they are most treatable. “If anyone has any change in their bowel habits, if they have any bleeding—even if they think it’s a hemorrhoid, and it doesn’t go away—just get a colonoscopy,” Dr. Reddy says.

At Smilow Cancer Hospital, Yale Medicine's colorectal surgeons treat a high volume of patients for all types of cancers of the colon and rectum. They work closely with other specialists, including oncologists, geneticists, gastroenterologists, and radiologists to determine the best treatment.

Nobody knows for sure why colorectal cancer numbers are rising in young people. Sedentary lifestyle, overweight and obesity, smoking, heavy alcohol use, low-fiber, high-fat diets or diets high in processed meats, and other environmental factors have all been associated with the disease. Family history of colorectal cancer or polyps, and conditions such as inflammatory bowel disease are also risk factors.

When someone is diagnosed with cancer at a young age, people also suspect genetics, but experts still haven’t been able to use genetics to explain the surge. The most common genetic condition associated with colon cancer is Lynch Syndrome, which typically involves tumors on the right side of the colon. But that’s not what’s causing these cases. Yale doctors are seeing a lot of young people whose colorectal cancer seems to be happening sporadically, as opposed to being caused by a particular genetic syndrome, Dr. Reddy says. 

Scientists at Yale and elsewhere are trying to learn more. “There may be other genes associated with predisposition for colorectal cancer that have yet to be discovered,” says Jessica DiGiovanna, MS, a licensed certified genetics counselor for the Smilow Cancer Genetics and Prevention Program. There are approximately 20,000 human genes, but scientists have only been able to map approximately one third of these genes to the human condition. For this reason, scientists are still working to identify genes that can help predict a person’s risk for particular diseases.

Meanwhile, researchers have been making progress in such areas as molecular tumor profiling, which analyzes DNA and other biological characteristics of tumor tissue samples. This can help determine treatment decisions.

Even though colorectal cancer is rising in young people, the incidence is still too low to justify routine colonoscopies for them. Once a screening test is developed for a disease, it's important to make sure that the number of screenings performed will prevent enough cancers to justify the costs of and risks associated with the tests. 

A colonoscopy is performed with the patient under conscious sedation. The doctor inserts a flexible tube with a light and camera on the end through the rectum to examine the colon. The tube also allows a doctor to remove any polyps (small bumps on the surface of the colon or rectum) that may be precancerous, heading off many cancers before they develop. For that reason, colonoscopy is considered to be one of the biggest reasons for the overall decrease in colorectal cancer.

Even before the most recent screening recommendation updates, experts have been recommending for several years that Black men and women start colorectal screening at age 45, since they are at higher risk. If you have a family history of the cancer, your doctor may recommend colonoscopy screening at 40 or 10 years before the age when your family member was diagnosed. Adults ages 76 to 85 should ask their doctor if they should be screened. Dr. Reddy prescribes colonoscopies for people of all ages who have symptoms such as rectal bleeding that they can’t diagnose with a different problem.

Short of a colonoscopy, Dr. Reddy recommends physical rectal exams in the office for anyone who reports a suspicious change in bowel movements. He says a simple rectal exam can often discover a suspicious mass in the rectum (although it can’t determine whether or not it’s cancerous). If the office exam turns up blood in the stool, the doctor can then send the patient for a colonoscopy.

If you’re not satisfied that your doctor has properly evaluated your symptoms, it’s smart to get a second opinion or even a third.

Young people—like everyone else—need to communicate with their doctor if they notice any of the following symptoms. 

• Rectal bleeding: This includes blood coming from the rectum, or blood in the stool or in the toilet after a bowel movement.
• Unusual stools: Watch for any changes in the way your stool looks. Keep an eye out for dark or black stools, which may indicate bleeding from a tumor. Talk to your doctor if you have stool that is narrow, thin or ribbon-like, which may signal that a tumor is obstructing your bowels or rectum.
• Changes in bowel movements: Look for loose stool (diarrhea) or constipation (less than three bowel movements a week), especially if the changes last two weeks or more.
• Low energy or tiredness: This could be due to anemia from blood loss. If you are a young woman with chronic anemia that you assume is due to menstrual bleeding, it’s a good idea to explore other causes as well.

Don’t assume anything.

“Even if you're in your 20s or 30s,” Dr. Pantel says, “you should get checked out if you have rectal bleeding, if you have any change in your bowel habits, any change in appetite (like feeling “full” early), weight loss, or abdominal pain that is not explained.” Your symptoms may be different than those of someone you know who had colorectal cancer. 

Stool entering a healthy colon (in the right side) is watery. But as it moves toward the end (left side) of the colon—and as fluid is absorbed—it becomes more solid, Dr. Pantel says. “So, a mass in the right colon may go unnoticed, because the loose stool is able to move past any mass until it nearly or completely obstructs the bowel.”

Many people misunderstand rectal bleeding as a symptom, Dr. Pantel adds. “So many patients are referred to me for treatment of hemorrhoids, but you need to make sure rectal bleeding is not something more serious—no matter how old the patient,” he says. 

Some people have no symptoms at all, so it’s important to talk to your doctor if colorectal cancer runs in your family. He or she may decide to recommend a colonoscopy before 45. Also, if a patient has seen a doctor and their symptoms still aren’t getting better, Dr. Pantel recommends a colonoscopy.

Don’t be afraid of the tests, either. Many people are put off by the preparation for a colonoscopy, which includes taking a strong laxative the day before to clean out the bowels. But colonoscopy is considered the gold standard for diagnosing colorectal cancers, and it saves lives.

To avoid colorectal cancer, consider making the following changes to your lifestyle:

• If you smoke, quit: That includes e-cigs. If you smoke, your risk is higher not only for lung cancers, but for colorectal and other cancers.
• Drink responsibly: The American Cancer Society advises no more than two drinks a day for men and one for women.
• Exercise: You have a greater risk of developing colorectal cancer if you are sedentary. Being more active might lower your risk.
• Lose weight: If you are overweight or obese, you have a higher risk of both developing colorectal cancer and dying from it. This is especially true for colon cancer.
• Consume adequate fiber: You should take in 25 grams of fiber a day to maintain a healthy colon. This means eating more fresh fruit, vegetables, whole grains, beans, and legumes. The typical American diet is 10 to 15 grams of fiber a day. 

While every case is different, the good news is that surgery for both colon and rectal cancers can be highly successful—even for many patients with advanced disease. While the treatment depends on the extent of the cancer, most patients will need surgery to remove the affected part of the colon. Some may need additional chemotherapy and some patients with rectal cancer may need radiation therapy, too. And some patients will need a colostomy, a procedure to connect the bowel to an opening in the abdomen for stool to pass through into a disposable bag. A colostomy may be temporary or permanent, depending on the surgery and, in some cases, the patient.

Surgery for rectal cancer is more highly specialized and intricate because of the location of rectal tumors—and the importance of preserving the ability to control bowel movements. Dr. Reddy says it's important to choose a surgeon who has done many of these procedures.

Even with good treatment, a cancer diagnosis can be emotionally devastating, says Philana Gydricza, a licensed clinical social worker and an oncology patient navigator for the Smilow Cancer Hospital. “Cancer is almost like an intruder in your house. It’s that level of threat,” she says. Gydricza helps patients navigate such matters as financial concerns, transportation, and family issues. It’s also important to seek out support beyond treatment—including social and psychological counseling. 

Many patients worry about how cancer treatment will affect their appearance and sexuality—especially if they are single and hope to have a long-term relationship in their future.

One such patient, a young single woman, brought a pile of clothes to the appointment at which doctors were going to mark a location on her body for a colostomy bag, which she would need to divert her bowel movements away from her colon after surgery. The staff worked with her to position the bag so that it wouldn’t create a visible lump. “She was very, very self-conscious,” Gydricza says, and her concerns were taken seriously.

Gydricza and other social workers do their best to make sure patients like this know they will be vital after treatment. “We tell them they still can be very sexy and beautiful,” she says.

[Are at-home colorectal cancer screenings right for you? Yale Medicine GI experts weigh in.]