Colorectal cancer screening saves lives. For average-risk adults, screening should start at age 45 and continue through 75, because it can find and remove precancerous polyps before they become cancer — and caught early, this cancer is highly treatable. Cases are rising in adults under 50, so younger adults with symptoms should not wait. You have several screening options, and the best test is the one you will actually complete. This article is general educational information, not medical advice; talk with your doctor about which screening is right for you, and see the warning signs below.
The American Cancer Society estimates roughly 158,000 new cases of colorectal cancer in the United States in 2026 (about 108,900 colon and 50,000 rectal cancers), and approximately 55,000 deaths — making it one of the most commonly diagnosed cancers and a leading cause of cancer death in both men and women. What makes colorectal cancer 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 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. This guide is educational only and is not a substitute for care from a qualified clinician.
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, can transform into cancer over a period that often spans 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 removal of polyps has been estimated to reduce colorectal cancer incidence and mortality substantially.
Colorectal cancers are predominantly adenocarcinomas, arising from the glandular cells that line the colon and rectum. Less common types include carcinoid (neuroendocrine) 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 still diagnosed in people over 50. However, incidence among adults under 50 has been rising steadily — by roughly 2 to 3 percent per year in recent decades (the American Cancer Society reports an increase of about 2.9 percent per year among people under 50 from 2013 to 2022) — and death rates in people under 55 have been creeping up about 1 percent per year since the mid-2000s. This early-onset trend prompted major screening-guideline changes and is a central reason the recommended start age was lowered to 45.
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 daily 50-gram serving (about two slices of deli meat) raising risk by roughly 16 percent.
Non-modifiable risk factors include a personal history of colorectal polyps or cancer, inflammatory bowel disease (ulcerative colitis or Crohn’s disease affecting the colon), a 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 roughly 5 to 10 percent of all colorectal cancers.
Type 2 diabetes is associated with an increased risk of colorectal cancer, independent of obesity. Black Americans have higher incidence and mortality rates than most other racial and ethnic groups; the reasons are multifactorial and include differences in screening rates, access to care, and potentially biological factors. Understanding your personal and family risk helps you and your doctor decide when to start screening and how often.
Symptoms and Warning Signs
Early-stage colorectal cancer frequently produces no symptoms, which is precisely why screening is so important. 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, or 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 hidden blood loss.
See a doctor promptly — and don’t assume it’s “just hemorrhoids” — if you have rectal bleeding or blood in the stool, a lasting change in bowel habits, unexplained weight loss, iron-deficiency anemia, or persistent abdominal pain. These have many causes, most not cancer, but they need evaluation, especially in anyone 45 or older who hasn’t been screened, or a younger adult with ongoing symptoms. Call 911 or go to the nearest emergency room for heavy rectal bleeding with lightheadedness or a rapid heartbeat, severe abdominal pain with distension and vomiting, or an inability to pass gas or stool with worsening pain — these can signal hemorrhage, bowel 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 personal preferences. People at higher-than-average risk — because of family history, a personal history of polyps, or inflammatory bowel disease — often need to start earlier and screen more frequently, on a schedule set by their doctor.
Multiple screening options are available, and the best one is the test you will actually complete:
- Colonoscopy every 10 years — the most complete test, allowing both detection and removal of polyps in a single procedure. Requires bowel preparation and sedation.
- Stool-based tests: the fecal immunochemical test (FIT) every year, or the multitarget stool-DNA test (Cologuard) every three years. These are non-invasive and done at home, but any positive result must be followed by a colonoscopy.
- CT colonography (virtual colonoscopy) every five years — uses CT imaging to visualize the colon without sedation, but still requires bowel preparation and cannot remove polyps.
- Blood-based test: in 2024 the U.S. FDA approved Shield (Guardant Health), a blood test for colorectal cancer screening in average-risk adults 45 and older — the first blood test approved as a primary screening option. It is drawn like an ordinary blood test, which may appeal to people who won’t do a colonoscopy or stool test. Important caveats: it is less sensitive than colonoscopy for early cancers and, in particular, is not good at detecting precancerous polyps, so it prevents fewer cancers than colonoscopy; a positive result must be followed by a colonoscopy. It is generally recommended on a roughly three-year interval, and Medicare covers an FDA-approved blood-based test that meets certain criteria.
- Flexible sigmoidoscopy every five years — examines only the lower third of the colon; used less commonly today.
Many gastroenterologists consider colonoscopy the preferred method because it is the most complete and can remove polyps during the same procedure, but non-invasive options (stool-based and blood-based tests) are valuable because they meaningfully increase the number of people who get screened at all. The worst screening test is the one that never gets done — so if a colonoscopy is a barrier for you, ask your doctor about an alternative rather than skipping screening.
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 has roughly a 90 percent 5-year survival rate, regional disease (spread to nearby lymph nodes) is in the ballpark of the low 70s percent, and distant (metastatic) disease is much lower, historically in the mid-teens percent — though survival for metastatic disease has been improving with newer therapies. These figures reflect averages over past years and cannot predict any individual’s outcome.
Beyond stage, several molecular and pathologic factors influence prognosis and treatment. 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 choice of chemotherapy and immunotherapy. Universal testing for Lynch syndrome through MMR/MSI testing of newly diagnosed colorectal cancers is now standard practice.
Treatment Approaches
Treatment is planned and directed by an oncology team and is tailored to the cancer’s stage, location, and molecular features, as well as the patient’s overall health. The overview below is for understanding, not self-management, and includes no dosing.
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 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 cancer outcomes. For rectal cancer, total mesorectal excision (TME) is the standard surgical technique, and advances in sphincter-sparing approaches have reduced the need for a permanent colostomy.
Chemotherapy
Adjuvant (post-surgery) chemotherapy is standard for stage III colorectal cancer and is used selectively for high-risk stage II disease. The FOLFOX regimen (a combination that includes 5-fluorouracil, leucovorin, and oxaliplatin) is among the most commonly used adjuvant regimens. The duration of adjuvant chemotherapy has been refined: research such as the IDEA collaboration showed that for many patients with stage III disease, a shorter course of oxaliplatin-based therapy is comparable to a longer one, with fewer side effects (particularly oxaliplatin-related nerve damage). Your oncologist determines the specific regimen and duration.
For metastatic colorectal cancer, systemic chemotherapy — often combined with targeted agents such as bevacizumab (which blocks tumor blood-vessel growth) or the EGFR-pathway drugs cetuximab and panitumumab (effective in certain RAS wild-type tumors) — can extend survival significantly. Some patients with limited liver or lung metastases are candidates for surgery to remove those metastases combined with chemotherapy, sometimes with curative intent.
Immunotherapy
Immunotherapy has become especially important for a specific subset: colorectal cancers with high microsatellite instability (MSI-H) or deficient mismatch repair (dMMR). A widely discussed study published in the New England Journal of Medicine reported that the checkpoint inhibitor dostarlimab produced a complete clinical response in a small group of patients with MSI-H rectal cancer, in some cases avoiding the need for surgery. This was an early, small study, and while longer follow-up and larger trials are ongoing, it points to a genuinely promising direction for selected patients. Immunotherapy is generally not effective for the more common tumors that are not MSI-H/dMMR.
Radiation Therapy
Radiation is used primarily for rectal cancer, often before surgery (neoadjuvant) to shrink the tumor and reduce recurrence risk. Short-course radiation and long-course chemoradiation are both established approaches, and “total neoadjuvant therapy” (combining chemotherapy and radiation before surgery) has become common for many rectal cancers. For colon cancer, radiation is used less frequently but may be considered in specific situations.
Prevention Beyond Screening
Beyond screening and polyp removal, lifestyle can meaningfully reduce colorectal cancer risk. The World Cancer Research Fund identifies strong evidence for several protective factors: regular physical activity, maintaining a healthy weight, a diet rich in whole grains and fiber, and limiting alcohol (no more than two drinks per day for men and one for women — and less is better).
Reducing red-meat consumption 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 has been shown to reduce colorectal cancer risk in some populations, but guidance on using it specifically for cancer prevention has been refined over time as the balance of cardiovascular benefits and bleeding risks has been re-evaluated; whether aspirin is appropriate for you is a decision to make with your doctor, not on your own.
For people with Lynch syndrome or other hereditary conditions, more intensive surveillance (typically colonoscopy every one to two years beginning in early adulthood) and, in some cases, preventive 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 side of cancer screening can help 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 50 in response to rising 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 generally begin at age 40, or 10 years before the youngest affected relative’s diagnosis, whichever comes first. Your doctor can help determine the right start age for you.
Is a colonoscopy painful?
Most patients report that the bowel preparation (drinking a laxative solution beforehand) is the most unpleasant part. The procedure itself is performed under sedation, and most patients feel little to no discomfort — many don’t remember it at all. A colonoscopy typically takes about 15 to 30 minutes, and mild bloating or cramping afterward is normal and resolves quickly.
What is the new blood test for colorectal cancer?
In 2024 the FDA approved Shield, a blood-based screening test for average-risk adults 45 and older — the first blood test approved as a primary colorectal cancer screening option. It is convenient because it only requires a blood draw, but it is less sensitive than colonoscopy, especially for detecting precancerous polyps, so it prevents fewer cancers; a positive result must be followed by a colonoscopy. It can be a reasonable option for people who would otherwise not get screened at all. Ask your doctor whether it’s appropriate for you.
Can colorectal cancer be cured?
Yes, particularly when caught early. Stage I colorectal cancer is curable with surgery alone in the large majority of cases. Stage II and III cancers are frequently curable with surgery plus chemotherapy when indicated. Even some patients with stage IV disease — particularly those with limited liver metastases that can be removed — can be cured with a combination of chemotherapy and surgery. Overall, a majority of people diagnosed with colorectal cancer survive five years or longer, and outcomes are best when the cancer is found early.
What does blood in the stool mean?
Blood in the stool has many possible causes, most of them benign — hemorrhoids, anal fissures, and diverticular bleeding are common. However, it 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 45 or older 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. Genetics play a role in some cases. This trend is what led to lowering the screening start age to 45. Young adults with 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 — a colonoscopy, an at-home stool test, a blood test, 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, most treatable 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. The remaining gap is action. Take it.
Sources
- American Cancer Society — colorectal cancer key statistics (2026 estimates)
- U.S. Preventive Services Task Force — colorectal cancer screening recommendation
- National Cancer Institute and SEER — colorectal cancer information and survival statistics
- Mayo Clinic — colon cancer symptoms and causes
- U.S. FDA — approval of the Shield blood-based colorectal cancer screening test (2024)
- World Cancer Research Fund — diet, activity, and colorectal cancer risk