The American Cancer Society estimates approximately 153,000 new cases of colorectal cancer in the United States in 2024, making it the third most common cancer in both men and women. What makes colorectal cancer particularly notable among malignancies is how preventable and treatable it is when caught early — screening can detect and remove precancerous polyps before they ever become cancer, and early-stage disease has a 5-year survival rate above 90 percent. Yet screening rates remain stubbornly below target, and a concerning rise in cases among younger adults has reshaped who should be thinking about this disease. Here’s what you need to know. For a broader look at major health conditions, see our medical conditions guide.
Understanding Colorectal Cancer
Colorectal cancer develops in the colon (the large intestine) or the rectum (the last several inches of the large intestine before the anus). Most colorectal cancers begin as polyps — small growths on the inner lining of the colon or rectum. Not all polyps become cancer, but certain types, particularly adenomatous polyps (adenomas) and sessile serrated polyps, have the potential to transform into cancer over a period typically spanning 10 to 15 years.
This slow progression from normal tissue to polyp to cancer — known as the adenoma-carcinoma sequence — is the biological basis for screening. By detecting and removing polyps during colonoscopy, the chain leading to cancer is broken. According to the National Cancer Institute, colonoscopy with polypectomy has been estimated to reduce colorectal cancer incidence by 40 to 60 percent and mortality by 50 to 60 percent.
Colorectal cancers are predominantly adenocarcinomas, arising from the glandular cells that line the colon and rectum. Less common types include carcinoid tumors, gastrointestinal stromal tumors (GISTs), lymphomas, and squamous cell carcinomas. The specific location within the colon matters clinically — right-sided colon cancers tend to have different molecular characteristics and present differently than left-sided or rectal cancers.
Risk Factors
Age is the single strongest risk factor. The majority of colorectal cancers are diagnosed in people over 50, with the average age at diagnosis being 66 for men and 69 for women. However, the incidence among adults under 50 has been rising steadily — approximately 1 to 2 percent per year since the mid-1990s — prompting major screening guideline changes.
Modifiable risk factors include obesity (particularly abdominal obesity), physical inactivity, diets high in red and processed meat, heavy alcohol use, and smoking. According to the World Cancer Research Fund, there is strong evidence that processed meat consumption increases colorectal cancer risk, with each 50-gram daily serving (about 2 slices of deli meat) raising risk by approximately 16 percent.
Non-modifiable risk factors include personal history of colorectal polyps or cancer, inflammatory bowel disease (ulcerative colitis or Crohn’s disease affecting the colon), family history of colorectal cancer (particularly a first-degree relative diagnosed before age 50), and inherited genetic syndromes. Lynch syndrome (hereditary nonpolyposis colorectal cancer, or HNPCC) and familial adenomatous polyposis (FAP) are the most significant hereditary conditions, together accounting for approximately 5 to 10 percent of all colorectal cancers.
Type 2 diabetes is associated with a 30 percent increased risk of colorectal cancer, independent of obesity. African Americans have higher incidence and mortality rates compared to other racial groups, though the reasons are multifactorial and include differences in screening rates, access to care, and potentially biological factors.
Symptoms and Warning Signs
Early-stage colorectal cancer frequently produces no symptoms, which is precisely why screening is so critical. When symptoms do develop, they can include a persistent change in bowel habits (diarrhea, constipation, or narrowing of the stool lasting more than a few days), rectal bleeding or blood in the stool, persistent abdominal discomfort (cramps, gas, pain), a feeling that the bowel does not empty completely, weakness and fatigue, and unexplained weight loss.
The Mayo Clinic emphasizes that rectal bleeding should always be evaluated, even in younger adults and even when hemorrhoids are present — hemorrhoids can coexist with cancer, and attributing bleeding to hemorrhoids without proper evaluation has been a documented cause of delayed diagnosis in younger patients.
Iron deficiency anemia — particularly in men and postmenopausal women — can be the first sign of a right-sided colon cancer that has been slowly bleeding. If blood work reveals iron deficiency anemia without an obvious cause, your doctor should consider evaluating the GI tract for occult blood loss.
When to seek emergency care: Call 911 or go to the nearest emergency room if you experience significant rectal bleeding with lightheadedness or rapid heartbeat, severe abdominal pain with distension and vomiting (suggesting bowel obstruction), or inability to pass gas or stool combined with worsening pain. These may indicate complications such as hemorrhage, obstruction, or perforation.
Screening: Your Best Defense
The U.S. Preventive Services Task Force recommends colorectal cancer screening for all average-risk adults beginning at age 45 and continuing through age 75. For adults aged 76 to 85, the decision to screen should be individualized based on overall health, life expectancy, prior screening history, and patient preferences.
Multiple screening options are available:
- Colonoscopy every 10 years — the gold standard, allowing both detection and removal of polyps in a single procedure. Requires bowel preparation and sedation.
- Stool-based tests: Fecal immunochemical test (FIT) annually, or multitarget stool DNA test (Cologuard) every 3 years. These are non-invasive and can be done at home, but positive results require follow-up colonoscopy.
- CT colonography (virtual colonoscopy) every 5 years — uses CT imaging to visualize the colon without sedation, but still requires bowel preparation and cannot remove polyps.
- Flexible sigmoidoscopy every 5 years — examines only the lower third of the colon; less commonly used today.
The best screening test is the one you actually complete. Many gastroenterologists consider colonoscopy the preferred method because of its completeness and therapeutic capability, but stool-based tests are valuable alternatives that significantly increase screening participation. People with higher-than-average risk — due to family history, personal history of polyps, or inflammatory bowel disease — typically need earlier and more frequent colonoscopy on a schedule determined by their gastroenterologist.
Staging and Prognosis
Colorectal cancer staging uses the TNM system, with stages ranging from 0 (carcinoma in situ, confined to the innermost lining) through IV (distant metastasis). Five-year relative survival rates reported by the National Cancer Institute’s SEER database illustrate the impact of stage at diagnosis: localized disease (stage I/II) has a 91 percent 5-year survival rate, regional disease (stage III, with lymph node involvement) drops to 73 percent, and distant disease (stage IV, metastatic) has a 14 percent 5-year survival rate.
Beyond stage, several molecular and pathologic factors influence prognosis and treatment decisions. Microsatellite instability (MSI) status, KRAS and BRAF mutation status, tumor sidedness, and mismatch repair (MMR) protein expression all have implications for both prognosis and the selection of chemotherapy and immunotherapy regimens. Universal testing for Lynch syndrome through MMR/MSI testing of all newly diagnosed colorectal cancers is now standard practice.
Treatment Approaches
Surgery
Surgery is the primary curative treatment for localized and regional colorectal cancer. The standard procedure is colectomy — removal of the cancer-containing segment of the colon along with surrounding lymph nodes. Minimally invasive (laparoscopic or robotic) surgery has become the norm for most colon cancers, offering faster recovery with equivalent oncologic outcomes. For rectal cancer, total mesorectal excision (TME) is the standard surgical technique, and advances in sphincter-sparing approaches have reduced the need for permanent colostomy.
Chemotherapy
Adjuvant (post-surgery) chemotherapy is standard for stage III colorectal cancer and selectively used for high-risk stage II disease. The FOLFOX regimen (5-fluorouracil, leucovorin, and oxaliplatin) is the most commonly used adjuvant regimen. The duration of adjuvant chemotherapy has been refined — the IDEA collaboration showed that for many patients with stage III disease, 3 months of FOLFOX is comparable to 6 months, with fewer side effects (particularly oxaliplatin-related neuropathy).
For metastatic colorectal cancer, systemic chemotherapy — often combined with targeted agents such as bevacizumab (which blocks tumor blood vessel growth) or cetuximab/panitumumab (which target the EGFR pathway, effective in KRAS wild-type tumors) — can extend survival significantly. Some patients with limited liver or lung metastases are candidates for curative-intent metastasectomy combined with chemotherapy.
Immunotherapy
Immunotherapy has emerged as a game-changer for a specific subset: colorectal cancers with high microsatellite instability (MSI-H) or deficient mismatch repair (dMMR). According to a landmark study published in the New England Journal of Medicine, the checkpoint inhibitor dostarlimab achieved a complete clinical response in every patient (100 percent) in a small trial of MSI-H rectal cancer, potentially eliminating the need for surgery entirely. While this represented a small cohort and longer follow-up is needed, it signals a transformative possibility for selected patients.
Radiation Therapy
Radiation is primarily used for rectal cancer, often given before surgery (neoadjuvant) to shrink the tumor and reduce recurrence risk. Short-course radiation (5 treatments over one week) and long-course chemoradiation (5 to 6 weeks of radiation combined with chemotherapy) are both established approaches. For colon cancer, radiation is used less frequently but may be considered for tumors adherent to adjacent structures.
Prevention Beyond Screening
Beyond screening and polyp removal, lifestyle modifications can meaningfully reduce colorectal cancer risk. The World Cancer Research Fund identifies strong evidence for the following protective factors: regular physical activity (at least 30 minutes of moderate activity daily), maintaining a healthy weight, a diet rich in whole grains and fiber, and limiting alcohol to no more than two drinks per day for men and one for women.
Reducing consumption of red meat (to less than 18 ounces of cooked meat per week) and avoiding processed meat are evidence-based dietary recommendations. Calcium and vitamin D may have modest protective effects, though supplementation solely for cancer prevention is not universally recommended. Aspirin use has been shown to reduce colorectal cancer risk in certain populations, and the USPSTF previously recommended low-dose aspirin for cancer prevention in select adults, though this recommendation has been refined as cardiovascular benefit-risk calculations have evolved.
For individuals with Lynch syndrome or other hereditary conditions, more intensive surveillance (typically colonoscopy every 1 to 2 years beginning at age 20 to 25) and, in some cases, prophylactic surgery are recommended. Genetic counseling and testing are appropriate for anyone with a strong family history of colorectal cancer or a pattern suggestive of a hereditary syndrome. Understanding the financial planning for cancer screening helps remove barriers to these preventive measures.
Frequently Asked Questions
At what age should I start screening for colorectal cancer?
For average-risk adults, screening should begin at age 45 based on current USPSTF and American Cancer Society guidelines. This was lowered from age 50 in response to rising colorectal cancer rates among younger adults. If you have a first-degree relative diagnosed with colorectal cancer before age 60, or two or more first-degree relatives diagnosed at any age, screening should begin at age 40 or 10 years before the youngest affected relative’s diagnosis, whichever is earlier.
Is a colonoscopy painful?
Most patients report that the bowel preparation (drinking a large volume of laxative solution the day before) is the most unpleasant part of the process. The procedure itself is performed under sedation — typically “twilight” sedation with propofol or a combination of midazolam and fentanyl — and most patients feel little to no discomfort. Many don’t remember the procedure at all. The entire colonoscopy typically takes 15 to 30 minutes. Mild bloating or cramping afterward is normal and resolves quickly.
Can colorectal cancer be cured?
Yes, particularly when caught early. Stage I colorectal cancer is curable with surgery alone in the vast majority of cases. Stage II and III cancers are frequently curable with surgery plus adjuvant chemotherapy when indicated. Even some patients with stage IV disease — particularly those with limited liver metastases — can be cured with a combination of chemotherapy and surgical resection. Overall, approximately 65 percent of colorectal cancer patients survive 5 years or longer.
What does blood in the stool mean?
Blood in the stool has many potential causes, most of which are benign — hemorrhoids, anal fissures, and diverticular bleeding are common culprits. However, blood in the stool can also be a sign of colorectal polyps or cancer. Bright red blood typically originates from the lower colon or rectum, while dark or tarry stools suggest bleeding higher in the GI tract. Any rectal bleeding should be evaluated by a doctor, especially if it persists, is accompanied by changes in bowel habits or weight loss, or occurs in someone over 45 who hasn’t been screened.
Why is colorectal cancer increasing in young adults?
The reasons for rising early-onset colorectal cancer are not fully understood, but researchers suspect a combination of factors: increasing obesity rates, more sedentary lifestyles, dietary shifts toward processed foods, changes in the gut microbiome, and possibly environmental exposures. Genetic factors may play a role in some cases. This trend led to the 2021 USPSTF recommendation to begin screening at 45 rather than 50. Young adults experiencing persistent rectal bleeding, changes in bowel habits, or unexplained abdominal symptoms should not delay medical evaluation.
Your Next Step
If you’re 45 or older and haven’t been screened, schedule your first colorectal cancer screening. Talk to your doctor about which method is right for you — whether that’s a colonoscopy, a stool-based test you can do at home, or another approved option. If you have a family history of colorectal cancer or polyps, ask whether you need earlier or more frequent screening.
If you’re experiencing symptoms — changes in bowel habits, rectal bleeding, unexplained weight loss, or persistent abdominal pain — don’t wait for your next scheduled screening. Get evaluated now. These symptoms have many possible causes, most of which are not cancer, but prompt evaluation ensures that if cancer is present, it’s found at the earliest possible stage.
Colorectal cancer is among the most preventable and treatable cancers when approached proactively. The tools exist — effective screening, proven prevention strategies, and increasingly sophisticated treatment options. The remaining gap is action. Take it.