Colorectal cancer, which includes both colon and rectal cancer, ranks as the third most common cancer and the third leading cause of cancer death in both men and women in the United States. The American Cancer Society (ACS) estimates approximately 153,020 new colorectal cancer cases will be diagnosed in 2024, resulting in approximately 53,230 deaths. However, there's exceptionally good news: colorectal cancer is largely preventable through screening and modifiable lifestyle factors. Unlike most cancers where screening simply detects existing disease, colorectal cancer screening can actually prevent cancer by identifying and removing precancerous polyps before they become malignant.

Understanding Colorectal Cancer Development

Most colorectal cancers develop from adenomatous polyps—abnormal growths on the inner lining of the colon or rectum. According to the National Cancer Institute (NCI), polyps are extremely common, occurring in approximately 30-40% of people by age 60. While most polyps never become cancerous, certain polyps—particularly adenomatous polyps larger than 1 cm—can progress to cancer over approximately 10-15 years. This slow progression from polyp to cancer creates an extraordinary prevention opportunity: finding and removing polyps prevents cancer from ever developing.

The NCI describes colorectal cancer as typically beginning as a polyp (adenoma), which over years accumulates genetic mutations that transform normal cells into precancerous and then cancerous cells. The adenoma-carcinoma sequence explains why screening can prevent, not just detect, colorectal cancer. When screening identifies and removes adenomatous polyps, it interrupts this progression, preventing colorectal cancer before it starts.

Approximately 10-15% of colorectal cancers develop through a different pathway called the serrated pathway, involving serrated polyps rather than traditional adenomas. Some serrated polyps, particularly sessile serrated lesions, carry cancer risk and should be removed when detected. Additionally, about 5-10% of colorectal cancers result from inherited genetic syndromes including Lynch syndrome and familial adenomatous polyposis (FAP), which require enhanced screening and management.

Several risk factors increase colorectal cancer likelihood. Non-modifiable risk factors include increasing age (more than 90% of colorectal cancers occur in people age 50 or older, though concerning recent increases in younger adults have been observed), personal history of colorectal polyps or inflammatory bowel disease (Crohn's disease or ulcerative colitis), family history of colorectal cancer or adenomatous polyps, inherited genetic syndromes, and type 2 diabetes. The ACS reports that modifiable risk factors include physical inactivity, diet high in red and processed meats, obesity, alcohol consumption, and smoking—all factors that can be changed to reduce risk.

Colorectal Cancer Screening: Multiple Effective Options

Colorectal cancer screening is one of the most powerful cancer prevention tools available. The ACS strongly recommends that adults at average risk begin regular screening at age 45. For older adults, screening should continue through age 75 for people in good health with life expectancy exceeding 10 years. For adults ages 76-85, screening decisions should be individualized based on patient preferences, overall health, prior screening history, and life expectancy. The ACS recommends against screening adults over age 85.

The U.S. Preventive Services Task Force recommends screening beginning at age 45 and continuing through age 75. For adults ages 76-85, the USPSTF recommends selective screening based on individual patient circumstances. The task force recommends against routine screening in adults over 85, as harms increasingly outweigh benefits in this age group who have limited life expectancy.

Several screening methods exist, each with distinct advantages and limitations. Colonoscopy remains the gold standard screening method. This procedure examines the entire colon using a flexible tube with a camera, allowing direct visualization of the colon lining. During colonoscopy, doctors can detect and immediately remove polyps, preventing cancer development. According to the NCI, colonoscopy detects approximately 95% of polyps and cancers, making it the most sensitive screening test. The ACS recommends colonoscopy every 10 years for average-risk adults starting at age 45, assuming results are normal.

The major advantage of colonoscopy is the ability to detect and remove polyps during the same procedure, combining screening with prevention. Research published by the NCI shows that colonoscopy with polypectomy reduces colorectal cancer incidence by approximately 76-90% and reduces mortality by approximately 68%. Disadvantages include the need for bowel preparation (consuming laxatives to clean the colon, which many patients find unpleasant), sedation (requiring someone to drive you home), procedure risks including bleeding and perforation (though serious complications occur in fewer than 1 in 1,000 procedures), and the need to take time off work or activities.

Flexible sigmoidoscopy examines only the rectum and lower portion (sigmoid colon) of the colon using a shorter flexible tube. The ACS recommends flexible sigmoidoscopy every five years, often combined with annual fecal immunochemical testing (FIT). Advantages include no sedation requirement, shorter procedure time, and less extensive bowel preparation than colonoscopy. However, sigmoidoscopy examines only about one-third of the colon, missing cancers or polyps in the upper colon. If polyps are detected, full colonoscopy is needed for complete examination and removal.

CT colonography (virtual colonoscopy) uses computed tomography imaging to examine the colon. After bowel preparation similar to colonoscopy, CT scans create detailed colon images that radiologists review for polyps or masses. The ACS recommends CT colonography every five years. Advantages include no sedation requirement and similar accuracy to colonoscopy for detecting polyps larger than 1 cm. Disadvantages include radiation exposure, the fact that if polyps are detected you'll need traditional colonoscopy for removal (meaning two bowel preparations), and reduced sensitivity for small polyps.

Stool-based tests detect signs of cancer or polyps in stool samples collected at home. The fecal immunochemical test (FIT) detects hidden blood in stool using antibodies specific to human hemoglobin. FIT is recommended annually. The test is simple, non-invasive, requires no bowel preparation or dietary restrictions, and can be done at home. However, FIT detects only about 74% of colorectal cancers and is less sensitive for polyps than visual exams like colonoscopy. Positive FIT results require follow-up colonoscopy.

The guaiac-based fecal occult blood test (gFOBT) also detects blood in stool but uses a chemical reaction. Like FIT, gFOBT is performed annually. It requires dietary restrictions (avoiding certain foods that can cause false-positive results) and detects approximately 50% of colorectal cancers, making it less sensitive than FIT.

The multi-targeted stool DNA test (mt-sDNA, Cologuard) detects both blood and DNA mutations associated with colorectal cancer and precancerous polyps. According to the ACS, this test is performed every three years. A study published in the New England Journal of Medicine found that mt-sDNA detected 92% of colorectal cancers and 42% of advanced adenomas, more sensitive than FIT. However, it has higher false-positive rates, costs more than FIT, and requires colonoscopy follow-up when positive.

Choosing the Right Screening Test

With multiple effective screening options, how do you choose? The ACS emphasizes that the best test is the one that gets done—any screening is better than no screening. Consider several factors when choosing. If you want the most thorough single examination and can tolerate bowel preparation and sedation, colonoscopy every 10 years is excellent. If you prefer avoiding sedation and invasive procedures, annual FIT or three-year mt-sDNA testing provides good alternatives, though colonoscopy is needed if results are abnormal.

If you have elevated risk due to family history, personal history of polyps, or inflammatory bowel disease, colonoscopy is generally recommended over stool tests because it's more sensitive and allows complete colon examination. The NCI recommends that people with first-degree relatives (parent, sibling, child) diagnosed with colorectal cancer or adenomatous polyps before age 60, or multiple affected first-degree relatives at any age, should begin colonoscopy screening at age 40 or 10 years younger than the age at which the youngest affected relative was diagnosed, whichever comes first.

For people with Lynch syndrome, colonoscopy should begin at ages 20-25 and be repeated every 1-2 years. People with familial adenomatous polyposis require even earlier and more frequent surveillance. Individuals with inflammatory bowel disease need colonoscopy surveillance beginning 8-10 years after disease onset, with frequency depending on disease extent and other risk factors.

Cost and insurance coverage may influence your choice. Most insurance plans, including Medicare, cover colonoscopy screening at no cost when coded as preventive screening. Stool-based tests are also typically covered. Check with your insurance provider about coverage for different screening options.

Dietary and Lifestyle Factors in Prevention

Beyond screening, substantial evidence demonstrates that dietary and lifestyle factors significantly influence colorectal cancer risk. The ACS estimates that approximately 50% of colorectal cancer cases could be prevented through healthy lifestyle choices combined with appropriate screening. Making evidence-based dietary and lifestyle modifications reduces your colorectal cancer risk while providing numerous other health benefits.

According to the NCI and World Cancer Research Fund/American Institute for Cancer Research (WCRF/AICR), strong evidence indicates that several dietary factors increase colorectal cancer risk. Red meat consumption (beef, pork, lamb) is associated with increased risk. The WCRF/AICR concludes that consuming more than about 18 ounces of cooked red meat weekly increases colorectal cancer risk. Red meat may increase risk through heme iron, heterocyclic amines and polycyclic aromatic hydrocarbons formed during high-temperature cooking, and N-nitroso compounds formed during digestion.

Processed meat consumption (meat preserved by smoking, curing, salting, or chemical preservatives—including bacon, sausage, hot dogs, ham, deli meats) shows even stronger association with colorectal cancer. The WCRF/AICR states there is convincing evidence that processed meat consumption increases colorectal cancer risk, with no identified safe threshold. The International Agency for Research on Cancer classifies processed meat as carcinogenic to humans based on colorectal cancer evidence.

To reduce risk, the ACS recommends limiting red meat consumption to no more than 18 ounces per week (cooked weight) and avoiding or minimizing processed meats. Choose chicken, fish, beans, and plant proteins more often than red or processed meats.

Alcohol consumption increases colorectal cancer risk in a dose-dependent manner—the more you drink, the higher your risk. According to the NCI, people who regularly drink 2-3 alcoholic drinks daily have approximately 20% higher colorectal cancer risk compared to non-drinkers. The ACS recommends limiting alcohol consumption to no more than one drink daily for women and two drinks daily for men, though less is better for cancer prevention.

Conversely, several dietary factors may reduce colorectal cancer risk. Dietary fiber from whole grains, fruits, vegetables, and legumes is associated with reduced colorectal cancer risk. The WCRF/AICR reports probable evidence that foods containing dietary fiber decrease colorectal cancer risk. Fiber may reduce risk by speeding transit time of potential carcinogens through the colon, diluting carcinogens, and producing beneficial short-chain fatty acids during fermentation by gut bacteria. Aim for at least 25-30 grams of fiber daily from food sources.

Calcium and vitamin D have been associated with reduced colorectal cancer risk in multiple studies. The NCI reports that adequate calcium intake (1,000-1,200 mg daily from food and supplements) may reduce risk. However, very high calcium intake might increase prostate cancer risk in men, so staying within recommended ranges is important.

Dairy products are associated with reduced colorectal cancer risk, possibly through calcium, vitamin D, or other components. Whole grains (brown rice, whole wheat bread, oatmeal, quinoa) contain fiber, vitamins, minerals, and phytochemicals that may reduce risk. The WCRF/AICR recommends making whole grains a substantial part of your usual diet.

Physical Activity, Body Weight, and Other Lifestyle Factors

Physical activity is one of the most consistently documented factors associated with reduced colorectal cancer risk. According to the ACS, people who are physically active have approximately 19% lower risk of colon cancer compared to the least active people. The NCI reports that physical activity may reduce risk through multiple mechanisms including reducing inflammation, improving immune function, regulating insulin and insulin-like growth factors, reducing body fat, and speeding transit time through the colon.

The ACS recommends adults engage in at least 150 minutes of moderate-intensity aerobic activity or 75 minutes of vigorous-intensity activity weekly (or a combination), preferably spread throughout the week. Greater amounts of activity provide additional benefit. Reduce sedentary behavior—limit time sitting and watching television, as sedentary behavior is independently associated with increased colorectal cancer risk.

Maintaining a healthy body weight significantly impacts colorectal cancer risk. The NCI states that obesity (body mass index 30 or higher) increases colorectal cancer risk by approximately 30-50% compared to healthy weight. Abdominal obesity (excess fat around the waist) shows particularly strong association with colorectal cancer. Obesity may increase risk through chronic inflammation, elevated insulin and insulin-like growth factors, and sex hormone alterations.

If you're overweight or obese, even modest weight loss reduces risk. The ACS recommends achieving and maintaining a body weight within the healthy range (BMI 18.5-24.9), or at least avoiding weight gain. If you're at a healthy weight, stay there through balanced diet and regular physical activity.

Smoking is associated with increased colorectal cancer risk and death. According to the NCI, long-term smokers have 30-40% higher risk of dying from colorectal cancer compared to non-smokers. Smoking may contribute to colorectal cancer development by introducing carcinogens into the digestive system, promoting inflammation, and impairing DNA repair. If you smoke, quitting reduces your colorectal cancer risk (in addition to dramatically reducing risk of lung cancer, heart disease, and numerous other conditions).

Aspirin and NSAIDs have been shown in multiple studies to reduce colorectal cancer risk. However, these medications also carry risks including gastrointestinal bleeding and cardiovascular effects. The U.S. Preventive Services Task Force recommends against routine use of aspirin for colorectal cancer prevention in most adults due to the balance of benefits and harms. However, for individuals at high risk for colorectal cancer and low risk for bleeding, discussing daily low-dose aspirin with your healthcare provider might be appropriate.

Living After Colorectal Cancer: Survivorship and Surveillance

For the approximately 1.5 million colorectal cancer survivors in the United States, ongoing surveillance and healthy lifestyle habits are crucial. The ACS recommends regular follow-up including physical examinations, colonoscopy surveillance, and sometimes blood tests (including carcinoembryonic antigen, or CEA) and imaging to detect recurrence early when it's most treatable.

Colonoscopy surveillance after polyp removal or cancer treatment follows specific schedules based on findings. The NCI provides guidelines: after removal of 1-2 small tubular adenomas with low-grade dysplasia, repeat colonoscopy in 5-10 years; after removal of 3-4 adenomas or any adenoma 10 mm or larger, repeat in 3 years; after removal of 5-10 adenomas, consider repeat in 1 year (potential for underlying genetic syndrome); and after removal of 10 or more adenomas, repeat within 1 year and consider genetic testing for polyposis syndromes.

Lifestyle modifications improve outcomes for colorectal cancer survivors. Research shows that regular physical activity after diagnosis reduces colorectal cancer recurrence and death. The ACS recommends colorectal cancer survivors engage in at least 150 minutes of moderate-intensity physical activity weekly. Maintaining a healthy body weight, limiting alcohol, avoiding smoking, and eating a diet rich in vegetables, fruits, whole grains, and fiber while limiting red and processed meats all support better outcomes.

Colorectal cancer is highly preventable through screening and healthy lifestyle choices. By undergoing recommended screening, maintaining a healthy weight, staying physically active, eating a diet rich in fiber and whole grains while limiting red and processed meats, and avoiding smoking and excessive alcohol, you can dramatically reduce your colorectal cancer risk. These same strategies benefit survivors by reducing recurrence risk and improving overall health and longevity.