Version July 2025
INTRODUCTION —
Colorectal cancer (CRC) is a common and lethal cancer worldwide and one of the leading causes of cancer death in the United States.
This topic describes strategies for CRC screening in the general population at average risk for CRC. Screening is intended for patients without signs or symptoms of possible CRC. Details regarding individual tests for CRC screening and their administration, advantages, disadvantages, and efficacy are discussed separately. (See "Tests for screening for colorectal cancer".)
CRC epidemiology, including incidence, mortality rates, and variability by sex, age, and portion of the colon, is described in detail separately. (See "Epidemiology and risk factors for colorectal cancer", section on 'Epidemiology'.)
Recommendations for patients at increased risk are described in detail separately:
●(See "Familial adenomatous polyposis: Screening and management of patients and families".)
●(See "Juvenile polyposis syndrome", section on 'Screening and management'.)
●(See "Clinical manifestations, diagnosis, and prognosis of ulcerative colitis in adults".)
●(See "MUTYH-associated polyposis", section on 'Colorectal cancer surveillance'.)
For patients with colon polyps that require follow-up surveillance for CRC, recommendations are described separately. (See "Overview of colon polyps".)
SCREENING RATIONALE
Natural history of colorectal cancer and colon polyps — Most CRCs arise from precancerous colon polyps that progress from small (<8 mm) to large (≥8 mm) polyps, then to dysplasia and carcinoma. Adenomatous polyps occur in approximately 30 percent of men and approximately 20 percent of women above age 40 to 50. A colon polyp must be biopsied to determine its pathology because gross appearance does not reliably distinguish adenomatous polyps from hyperplastic polyps, which are typically not precancerous.
Progression from polyps to carcinoma is believed to take approximately 10 years. This estimate is imprecise and may not apply to all types of polyps. The clinical presentation and natural history of colon polyps are described in detail separately. (See "Overview of colon polyps".)
Benefits of screening — We suggest that average-risk individuals ages 45 to 75 years undergo screening for CRC. CRC incidence and mortality rates have been declining in the United States, likely due to an increase in screening [1-3]. (See "Epidemiology and risk factors for colorectal cancer", section on 'Epidemiology'.)
CRC is moderately common, with a lifetime incidence of 4 percent in average-risk individuals in the United States (see "Epidemiology and risk factors for colorectal cancer", section on 'Incidence'). Estimates from observational studies and randomized trials suggest that CRC screening reduces CRC mortality by approximately 16 to 24 deaths per 1000 persons screened (figure 1).
Screening tests for CRC can improve disease prognosis by identifying early-stage CRC that is easier to treat and has a lower mortality rate than CRC detected after symptoms develop. In addition, screening can prevent CRC by detecting and removing premalignant polyps before they progress to CRC.
Across the multiple strategies that are recommended for screening by major guidelines, the numbers of CRC deaths averted appear to be relatively similar, although the sensitivity and specificity for detecting polyps and CRC vary, as shown in a figure (figure 1). A mortality benefit has been demonstrated in randomized clinical trials for guaiac-based fecal occult blood testing (gFOBT) and sigmoidoscopy. A potential mortality benefit is inferred for other screening tests based on observational studies and comparisons with studies of other screening strategies that have undergone randomized, controlled trials. The types of evidence supporting efficacy of each CRC screening strategy are discussed in detail separately. (See 'Test selection' below and "Tests for screening for colorectal cancer".)
Harms associated with screening — Most of the harms of screening for CRC are related to the risks from colonoscopy and sigmoidoscopy, including perforation. Any abnormal results of initial screening tests other than colonoscopy (eg, stool-based test, virtual colonoscopy) necessitate a colonoscopy to evaluate the abnormality; thus, all screening modalities are associated with the potential for colonoscopy-associated complications [4,5]. In a meta-analysis of over 335,000 individuals screened initially by either FOBT or sigmoidoscopy with positive results followed up with colonoscopy, a major complication was recorded in 0.08 percent of participants, including 0.03 percent who initiated screening with FOBT [6]. In older adults, colonoscopy carries increased risk of complications. Complications of colonoscopy are described in detail separately. (See "Overview of colonoscopy in adults", section on 'Adverse events'.)
Cost and cost effectiveness — The cost of the various screening tests for CRC varies over a wide range, from a few US dollars for gFOBT to USD $1000 or more for colonoscopy. Models regarding the cost-effectiveness (cost per year of life saved) of CRC screening come to somewhat different conclusions because they make different assumptions. The cost per year of life saved is within the generally accepted range in the United States (USD $50,000), relative to no screening, for all of the recommended CRC screening tests [7]. As an example, in one analysis, the cost per year of life saved was USD <$15,000 for all recommended tests, compared with no screening [8]. In a microsimulation study that compared noninvasive CRC tests in a United States community clinic population, annual fecal immunochemical testing was the most effective, cost-saving strategy, even in realistic (imperfect) adherence scenarios [9]. Triennial blood-based CRC testing was least effective, even with perfect adherence.
ASSESSING RISK FOR COLORECTAL CANCER —
The first step in screening is identifying the patient's level of risk for CRC because level of risk impacts screening and follow-up recommendations. For this purpose, patients are generally determined to be either at average risk or at increased risk.
We assess the risk for CRC at the initial visit for an adult who is age 20 years or older, unless a genetic risk is already known and documented, to identify high-risk patients who should begin CRC screening at an earlier age than those at average risk. Subsequent reassessment every three to five years identifies whether the patient or their biologic family members have developed factors that raise the patient's level of risk for CRC. Although there are no published guidelines supporting this approach, one study from a United States national population-based cancer registry found that the number of patients who would meet criteria for high-risk screening based on family history significantly increased from age 30 (2.1 percent) to age 50 (7.1 percent), supporting the need to update the family history [10].
Factors important to determine CRC risk can be assessed by asking several questions. A "no" response to all of these questions generally indicates average risk.
●Have you ever had CRC or a precancerous polyp? A personal history of CRC increases the risk of another primary (metachronous) cancer. Surveillance following CRC is discussed separately. (See "Post-treatment surveillance for colorectal cancer", section on 'Diagnosing second cancers and polyps'.)
A personal history of precancerous colorectal polyps increases the risk of CRC [11,12]. Precancerous colon polyps include adenomas and serrated polyps. The number and types of polyp lesions guide the determination of the appropriate interval for surveillance. Recommendations for follow-up are described separately. (See "Overview of colon polyps", section on 'Surveillance'.)
If the patient's personal polyp history is uncertain, records should be obtained to determine if the patient had an adenomatous polyp. If records cannot be obtained, the patient may recall being told a polyp was found and advised to have a follow-up colonoscopy in five years or sooner, suggesting the polyp was adenomatous or a sessile precancerous lesion.
●Have any biologic family members had CRC or a documented advanced polyp? An advanced polyp is defined as an advanced adenoma (adenoma ≥1 cm, or with high-grade dysplasia, or adenoma with tubulovillous or villous histology [13]) or advanced serrated lesion (sessile serrated polyp [SSP] ≥1 cm, or traditional serrated adenoma ≥1 cm, or SSP with cytologic dysplasia).
If so, how many biologic family members, were they first-degree relatives (parent, sibling, or child), and at what age was the cancer or polyp first diagnosed? Enhanced screening is warranted for a patient with increased risk of CRC due to a family history of CRC or documented advanced polyp and is described in detail separately. (See "Screening for colorectal cancer in patients with a family history of colorectal cancer or advanced polyp".)
If a biologic family member is reported to have had a polyp but there is lack of available documentation about the type of polyp, the patient is typically screened as if a family member did not have an advanced polyp. (See "Screening for colorectal cancer in patients with a family history of colorectal cancer or advanced polyp", section on 'Assessing risk due to family history'.)
If the patient cannot obtain any family history whatsoever related to CRC or polyps, some experts suggest screening the patient as average risk, although no studies have evaluated that approach.
●Do you have biologic family members with any of the known genetic syndromes that can cause CRC? Patients with a family history of a known genetic syndrome for CRC may require enhanced screening plus genetic counseling. These syndromes and associated screening recommendations are discussed in detail separately:
•(See "Familial adenomatous polyposis: Screening and management of patients and families".)
•(See "Juvenile polyposis syndrome", section on 'Screening and management'.)
•(See "MUTYH-associated polyposis", section on 'Colorectal cancer surveillance'.)
●Do you have inflammatory bowel disease (ulcerative colitis or Crohn disease)? Patients with inflammatory bowel disease (IBD) of the colon (ulcerative colitis or Crohn disease) have an increased risk of CRC. The approach to surveillance for CRC in patients with IBD is discussed separately. (See "Surveillance and management of dysplasia in patients with inflammatory bowel disease", section on 'Approach to surveillance'.)
●Did you receive abdominal radiation for childhood cancer? Adults who received abdominal radiation in childhood for malignancy are at increased risk of CRC. Enhanced screening recommendations are described separately. (See "Epidemiology and risk factors for colorectal cancer", section on 'Abdominopelvic radiation'.)
Other risk factors that may influence screening advice include:
●HIV infection in men – For males who are living with human immunodeficiency virus (HIV), the risk for cancer in the colon seems to be similar to the general population risk, so screening strategies for CRC should be based on other risk factors the patient has [14].
Males living with HIV have an increased risk for anal neoplasia (though not for colon cancer) compared with the general population. Specific screening recommendations for anal cancer are described separately. (See "Anal squamous intraepithelial lesions: Epidemiology, clinical presentation, diagnosis, screening, prevention, and treatment", section on 'Screening for anal SIL'.)
●Additional risk factors for CRC, including lifestyle matters (eg, dietary factors, obesity, alcohol use, smoking) that may impact CRC risk, are discussed in detail separately. (See "Epidemiology and risk factors for colorectal cancer", section on 'Factors that may influence screening recommendations'.)
A detailed discussion of risk factors for CRC is presented separately. (See "Epidemiology and risk factors for colorectal cancer".)
SOCIAL FACTORS AND HEALTH EQUITY —
In the United States, incidence rates and mortality for CRC are higher among Native American/Alaskan Native; Native Hawaiian; other Pacific Islander; and Black people, particularly Black males, than among those in other racial or ethnic groups [15]. CRC incidence is also disproportionately high in geographic locations such as the Mississippi Delta region and the Appalachian region that are correlated with socioeconomic disadvantage [16,17]. Disparities in incidence and mortality among Black people are apparent even prior to the age recommended for initiating screening in people at average risk for CRC.
Several factors have been shown to contribute to disparities, including disproportionate rates of exposure to risk factors, historical social injustices, and barriers to access to screening and other preventive services. Disparities have also been documented in the quality of screening and care received, such as delays in initiation of treatment [18,19]. A report by the United States Preventive Services Task Force (USPSTF) found an extensive body of literature on implementation strategies for delivering preventive care services, including CRC screening [20,21]. The USPSTF encouraged development of delivery services to ensure equitable access to high-quality care from screening through treatment, particularly for people from groups that experience disproportionate incidence, late-stage diagnosis, and death from CRC. Studies in the managed care organizations and safety net settings have shown that system-based coordinated strategies for equitable delivery of screening and follow-up care can address structural barriers and reduce or even eliminate disparities [22-24]. Examples of specific systems-based interventions include patient navigation and reminder systems [25]. (See "Epidemiology and risk factors for colorectal cancer", section on 'Race and sex'.)
AGE TO INITIATE SCREENING —
We initiate screening at age 45 years in adults at average risk; this approach balances the benefits of detection and prevention with the burden on the patient and the risk of harms from screening [26]. (See 'Benefits of screening' above.)
In individuals ages 45 to 49, the net benefit of CRC screening is likely moderate; however, it is less well established than in individuals ages 50 to 75. CRC incidence is generally lower in younger individuals, and most trials and observational studies of CRC screening did not include participants younger than age 50 (figure 2) [27]. However, studies that included participants younger than age 50 have not shown differences in the relative benefits and harms with screening or the accuracy of screening tests in the 45- to 49-year-old age group [27,28].
The suggested age to initiate CRC screening varies among professional guidelines:
●The United States Preventive Services Task Force recommends initiating screening at age 45 (Grade B) while maintaining its strongest recommendation (Grade A) for initiating at age 50 [26].
●The 2021 American College of Gastroenterology guidelines also recommend initiating screening at age 45 in adults at average risk [29].
●Initiating screening at age 45 years is a "qualified" recommendation from the American Cancer Society (ACS) and a strong recommendation at age 50 and older [5,30]. The ACS noted that data to support starting at age 45 years are limited; the rationale is supported from some but not all modeling analyses [31].
●Initiating screening at age 50 years for average-risk adults is recommended by the Canadian Task Force on Preventive Health Care (CTFPHC), the European Council, the American Academy of Family Physicians, and the American College of Physicians (ACP) [32-35].
DISCONTINUING SCREENING —
The decision about when to discontinue screening should be individualized based on shared decision-making, taking into account the patient's risk for CRC, prior screening history, personal values, and whether the patient's comorbid conditions and life expectancy justify the risks of continued screening [36-39].
We continue to screen for CRC through age 75 years for average-risk patients, as long as their life expectancy is 10 years or greater. Screening at least until age 75 years for patients at average risk for CRC is recommended by the United States Preventive Services Task Force and many other guidelines [5,26,32-35,40]. This is based on the increasing frequency of CRC with age and the time course of progression from polyp to CRC.
For older adults who have never been screened, results of a modeling study suggest that one-time screening appears to be cost-effective up to an age that varies depending on the patient's life expectancy, comorbidities, and the test used for screening [41]. As an example, for patients at average risk for CRC and without any comorbidities, in the simulation study, assuming a willingness to pay USD $100,000 per quality-adjusted life-year gained, colonoscopy was cost-effective to age 83 years, sigmoidoscopy to 84 years, and fecal immunochemical testing to 86 years. In that study, colonoscopy was the most effective, due to its overall effectiveness for both CRC and adenomas, and was also the most expensive strategy for one-time screening.
For patients aged 76 to 85 years who have been screened before, we individualize the decision about whether to continue screening, based on factors including the patient's preferences, prior testing results, and comorbidities. Some guidelines recommend not continuing screening, whereas others recommend that the decision to screen adults 76 to 85 years be individualized, taking into account the patient's overall health and prior screening history [5,26,32,40,42,43]. Data supporting continued screening are limited; trials have included too few older patients to provide reliable evidence-based guidance about the balance of benefits and harms of screening beyond age 75 years. A prospective observational study of Medicare beneficiaries found that undergoing colonoscopy modestly decreased the risk of developing CRC over an eight-year period for those aged 70 to 74 years (2.2 versus 2.6 percent in the no-screening group), with a non-significant decrease in risk for those 75 to 79 years. In a modeling study of adults aged 65 years at average risk for CRC with average life expectancy and negative colonoscopy at age 55, extending screening beyond age 75 resulted in net harm (loss of quality-adjusted life-years) due to complications from colonoscopy.
Shortened life expectancy modifies these age guidelines. Patients with a life expectancy less than 10 years (some would say five years) would not be expected to benefit from colorectal screening, since studies indicate benefit from screening in a population starts to accrue after approximately five years. For example, in a meta-analysis of screening with sigmoidoscopy, an absolute risk reduction of one CRC-related death for every 5000 sigmoidoscopies was observed at 4.3 years, and an absolute risk reduction of one CRC-related death for every 1000 sigmoidoscopies occurred by 9.4 years [44]. In one modeling study, screening patients ages 67 to 69 with three or more comorbidities would save fewer lives than screening older patients (ages 75 to 79) with no comorbidity (81 versus 459 lives saved per 100,000) [45]. Some guidelines recommend stopping screening for CRC when the patient's life expectancy is less than 10 years [40].
CHOOSING A SCREENING TEST
Test selection — In patients at average risk for CRC, we suggest screening with either colonoscopy or fecal immunochemical testing (FIT). Other screening strategies include multitarget stool deoxyribonucleic acid (mt-sDNA) testing (Cologuard); high-sensitivity guaiac-based fecal occult blood testing (gFOBT), such as Hemoccult SENSA; computed tomography (CT) colonography (CTC); and flexible sigmoidoscopy.
This approach is based on the quality of evidence regarding different test options and considerations of test accuracy, convenience, and acceptability. However, because test adherence is essential to the success of screening, the choice among these tests also depends on patient preference and test efficacy and availability.
●Comparative test performance – Only a few randomized trials have compared the efficacy of different CRC screening tests in improving clinically important outcomes, such as death, for CRC. In a population-based trial of 57,404 adults in Spain who were ages 50 to 69 years and at average risk for CRC, invitation to FIT screening was comparable to invitation to colonoscopy in reducing the risk of CRC mortality at 10 years (0.24 versus 0.22 percent in the intention-to-screen analysis; risk difference -0.02; 95% CI -0.10 to 0.06) [46]. FIT was also comparable to colonoscopy for detecting CRC, with an incidence of CRC at 10-year follow-up of 1.35 percent in participants randomized to colonoscopy versus 1.22 percent in those randomized to FIT (risk difference 0.09 percent, 95% CI -0.28 to 0.10). Participation in any form of CRC screening was higher in the group randomized to FIT (40 versus 32 percent). Results from this trial underscore the importance of test adherence for the efficacy of population-based CRC screening strategies. A second comparative efficacy trial of the effectiveness of screening colonoscopy versus stool-based testing is ongoing [47].
Data from multiple randomized trials support the efficacy of gFOBT, sigmoidoscopy, and, possibly, colonoscopy in reducing mortality from CRC, compared with usual care. Efficacy data for other CRC screening tests derive from observational studies, modeling studies, or comparisons of test accuracy. Details regarding test efficacy and other characteristics of specific testing options for CRC screening are discussed separately (figure 1). (See "Tests for screening for colorectal cancer".)
mt-sDNA testing (Cologuard) includes FIT plus DNA assays, so its accuracy may be similar to that of FIT; however, its mortality benefits have not yet been confirmed in randomized trials (see "Tests for screening for colorectal cancer", section on 'Multitarget stool DNA tests with fecal immunochemical testing'). Although screening CTC has reasonable test accuracy compared with colonoscopy, its efficacy for reducing CRC mortality has not been established in randomized trials (see "Tests for screening for colorectal cancer", section on 'Computed tomography colonography'). Screening with gFOBT reduces CRC mortality; however, we prefer FIT to gFOBT because FIT is more accurate and gFOBT requires multiple stool samples and diet modifications (see "Tests for screening for colorectal cancer", section on 'Guaiac-based fecal occult blood test (gFOBT)'). Screening with flexible sigmoidoscopy also reduces deaths from CRC, but this benefit appears limited to distal (left-sided) CRCs. (See "Tests for screening for colorectal cancer", section on 'Sigmoidoscopy'.)
●Role of patient preference – Because existing evidence does not document the unequivocal superiority of specific CRC screening tests, we use patient preferences to help guide test selection. After determining that a patient is at average risk for CRC, we initiate the discussion regarding CRC screening by suggesting screening (see 'Assessing risk for colorectal cancer' above). We then engage in shared decision-making by eliciting individual patient preferences and values; conveying the individual's risk of CRC; and discussing test effectiveness, safety, availability, frequency, convenience, comfort, and cost.
●Importance of adherence – The best screening test is one that the patient is willing to complete according to the test instructions [26]. Completing screening with a guideline-recommended test that is acceptable to the patient is preferable to having the patient decline screening because of not being given screening test options that fit with their preferences [5,26].
Randomized trials have found that participation rates for participants assigned to screening with FIT were greater than with stool guaiac, sigmoidoscopy, or colonoscopy [46,48,49]. This suggests that patients may prioritize convenience and ease of testing without the need for dietary restrictions or multiple stool samples. Noninvasive screening tests such as FIT, mt-sDNA testing, and stool guaiac can be given or mailed directly to patients to complete in the comfort of their homes.
Although findings from these studies may inform discussions about CRC screening, they represent the average preference for groups of patients and should not dictate test selection for individual patients.
Test options — Guidelines from professional organizations recommend different tests for CRC screening. A 2019 guidance statement from the American College of Physicians provides a summary and appraisal of various guidelines on CRC screening, as well as information on recommended screening tests [50].
The following section summarizes recommendations regarding test selection and screening strategies. Details regarding the test procedure and the advantages and disadvantages of specific tests are discussed separately. (See "Tests for screening for colorectal cancer".)
●Preferred tests – These include colonoscopy and FIT:
•Colonoscopy – For patients at average risk of CRC who prefer colonoscopy, we perform colonoscopy every 10 years. Screening with colonoscopy appears to have similar efficacy as FIT for reducing incidence and mortality from CRC. Among screening tests, colonoscopy has the highest sensitivity for detecting adenomatous polyps (figure 1) and allows lesion removal anywhere in the colon during just one procedure. Consequently, it offers the potential to detect and prevent cancer by removing adenomatous polyps prior to malignant transformation. (See "Tests for screening for colorectal cancer", section on 'Colonoscopy'.)
The frequency of follow-up for patients with findings on a colonoscopy is described separately. (See "Overview of colon polyps", section on 'Surveillance'.)
When an adequate screening colonoscopy is accomplished, intercurrent stool tests (ie, between colonoscopy examinations) are not necessary. In addition, for patients who have had a negative colonoscopy and have been recommended to have routine screening in 10 years, screening with FIT or other screening tests is not indicated prior to the end of the 10-year period. The lower risk of CRC mortality associated with a negative colonoscopy may extend up to 15 years [51].
Colonoscopy is recommended as a screening option by the United States Preventive Services Task Force (USPSTF), American Cancer Society (ACS), National Comprehensive Cancer Network (NCCN), and American Academy of Family Physicians (AAFP) and is in the most highly recommended tier of tests according to the United States Multi-Society Task Force (MSTF) on Colorectal Cancer [5,26,34,52,53]. It is a suggested alternative in the American Society of Clinical Oncology (ASCO) guideline and by the American College of Physicians (ACP) [35,54,55]. However, the Canadian Task Force on Preventive Health Care (CTFPHC) does not recommend using colonoscopy as a primary screening test [32].
•FIT – For patients at average risk of CRC who prefer FIT, we screen annually on a single stool sample. We offer FIT as a comparable alternative to colonoscopy or when access to colonoscopy is limited, with the understanding that if the FIT result is positive, colonoscopy needs to be performed promptly. FIT appears comparable to colonoscopy for reducing mortality from CRC and detecting CRC but has lower detection rates for advanced adenomas (figure 1) [46]. Compared with gFOBT, FIT has greater sensitivity, comparable specificity, and better detection of advanced adenomas [27,56-58]. (See "Tests for screening for colorectal cancer", section on 'Fecal immunochemical test (FIT) for blood'.)
FIT is recommended as a screening option by many expert groups. We prefer using a quantitative FIT with automated high-throughput analysis as the fecal test of choice for CRC screening, as recommended by a European consensus panel [59]. Annual testing with FIT is one of several options recommended by the USPSTF, which does not endorse test preferences [27]. In the United States, the MSTF recommends FIT as one of the first-tier (most highly recommended) choices [52]. ACP, ACS, AAFP, and ASCO include FIT as a screening option [5,34,35,54] and NCCN suggests it as an alternative test [53].
●Other tests – Other testing strategies appropriate for average-risk patients include the following:
•mt-sDNA testing – mt-sDNA, also known as FIT-DNA and multitarget fecal DNA, combines FIT and tests for DNA mutations and methylation. It is available as Cologuard in the United States. The test is performed every three years on one stool collection sample, but the USPSTF recommends use of mt-sDNA every one to three years. (See "Tests for screening for colorectal cancer", section on 'Multitarget stool DNA tests with fecal immunochemical testing'.)
mt-sDNA testing has a higher single-application sensitivity and a lower specificity than FIT for CRC and advanced precancerous lesions [60], and it is more expensive than FIT.
mt-sDNA testing is included as a second-tier choice by MSTF and is also recommended by the ACS, NCCN, and USPSTF [5,52,61].
•CTC – We advise CTC (formerly referred to as "virtual colonoscopy") as another option. CTC is performed every five years. CTC is more sensitive than any test other than colonoscopy to detect adenomatous polyps, although data are limited on other outcomes. Patients should understand that if CTC findings suggest polyps or CRC, colonoscopy is required promptly for evaluation. (See "Tests for screening for colorectal cancer", section on 'Computed tomography colonography'.)
For older patients with comorbidities (eg, cardiopulmonary disease, diabetes mellitus, or history of stroke), CTC might be preferred over colonoscopy, because the risks of colonoscopy increase with age [62]. However, patients with abnormal findings on CTC should undergo colonoscopy. Therefore, patients who choose CTC should also be candidates for colonoscopy.
CTC requires either a bowel preparation or oral ingestion of a preparation to tag stool so it can be electronically "removed" from the radiographic images. CTC exposes the patient to some abdominal radiation and may identify incidental abdominal findings that need follow-up to determine if they are of clinical significance. Detection of incidental extra-colonic findings also rises with increasing age, which can lead to testing and procedures that carry risks. The preparation, technique, and risks of CTC are described separately. (See "Computed tomographic (CT) colonography in adults".)
CTC is recommended as a second-tier option by MSTF, a suggested alternative by ASCO, and recommended by ACS [5,52,54,55]. NCCN did not come to consensus about CTC for screening [53].
•Sigmoidoscopy combined with FIT (or high-sensitivity gFOBT) – The combination of sigmoidoscopy with FIT or gFOBT theoretically enhances lesion detection by offering direct visualization up to 60 cm as well as by detecting colon lesions beyond the reach of a sigmoidoscope by testing for occult blood. FIT is preferred over sensitive gFOBT. However, evidence supporting this strategy is limited. (See "Tests for screening for colorectal cancer", section on 'Sigmoidoscopy plus FIT or gFOBT'.)
The recommended frequencies of each test vary among expert guidelines. USPSTF recommends sigmoidoscopy every 10 years with annual FIT, which is also an option in ASCO guidelines [26,54,55]. NCCN includes an option for sigmoidoscopy every five years with annual FOBT [53]. ACP includes sigmoidoscopy every 10 years plus combined FIT every two years [35].
•Sigmoidoscopy alone – If the option of adding a stool-based test is not available or practical for a patient to do in conjunction with sigmoidoscopy, then screening with sigmoidoscopy alone every 5 to 10 years may be offered.
Sigmoidoscopy can be performed with minimal patient preparation and does not require sedation. However, a sigmoidoscopy can only identify lesions up to the distal 60 cm of the bowel. This may be problematic in women and older patients because they have a higher frequency of more proximal lesions. (See "Tests for screening for colorectal cancer", section on 'Sigmoidoscopy'.)
Evidence from large, randomized trials supports the efficacy of screening sigmoidoscopy in reducing mortality from CRC (see "Tests for screening for colorectal cancer", section on 'Evidence of effectiveness'). Recommendations for how often to perform screening with sigmoidoscopy alone vary among guidelines. Sigmoidoscopy every five years is a screening option recommended by the USPSTF and other groups [5,26,54,55]. MSTF includes it as an option to be performed every 5 to 10 years, and CTFPHC includes sigmoidoscopy every 10 years [32,52].
•gFOBT – If this method is chosen, the sensitive gFOBT (eg, Hemoccult SENSA) should be used. gFOBT is done annually on three samples as a take-home test that the patient mails back, rather than on stool obtained during a digital rectal examination (DRE). Stool obtained by DRE should not be used for CRC screening.
Some clinicians advise dietary restrictions during testing, though these restrictions may limit patient adherence to testing and thus some clinicians no longer restrict diet during testing. It typically takes at least three days to complete the testing due to the number of samples needed; however, bowel preparation and sedation are not needed.
Stool guaiac tests (gFOBT) have low sensitivity for polyps and relatively low specificity for clinically important disease. Additionally, gFOBT needs to be repeated annually if negative. (See "Tests for screening for colorectal cancer", section on 'Guaiac-based fecal occult blood test (gFOBT)'.)
Evidence from large, randomized trials supports the efficacy of gFOBT screening in reducing mortality from CRC (see "Tests for screening for colorectal cancer", section on 'Evidence of effectiveness'). gFOBT is included by the ACS, ASCO, and NCCN as an option to be done yearly, and by the ACP and CTFPHC to be done every two years; it was the only screening test recommended by the European Council in 2012 [5,32,33,53-55].
•Capsule colonoscopy – Capsule colonoscopy every five years is included in the MSTF guideline as a third-tier option, although it is not among the tests included in some screening guidelines [52]. In this test, the patient swallows a capsule containing tiny video cameras. A stool preparation is needed; however, sedation is not needed. In the United States, this test is approved by the US Food and Drug Administration (FDA) as an option for patients after an incomplete colonoscopy but not as a standalone screening method for CRC. (See "Tests for screening for colorectal cancer", section on 'Colon capsule endoscopy' and "Wireless video capsule endoscopy", section on 'Colon capsule endoscopy'.)
•mt-sRNA – Multitarget stool ribonucleic acid (mt-sRNA), also known as ColoSense, combines fecal testing for hemoglobin and RNA transcripts. The mt-sRNA test has a sensitivity of 94 percent for detecting CRC and 46 percent for detecting advanced adenomas. Its specificity is 88 percent for having no lesions on colonoscopy. This test is approved by the FDA but has not been recommended by the USPSTF [63].
Tests that are not recommended — Certain tests are not appropriate for CRC screening because they have lower accuracy than recommended testing strategies or evidence is lacking regarding their efficacy. These include DRE, office-based gFOBT after DRE, barium enema (single or double contrast), carcinoembryonic antigen (CEA), stool RNA tests (ColoSense), or other blood-based assays that test for CRC only or for multiple cancers (ie, multicancer early detection tests) [64].
●Blood-based tests – Several blood-based tests that detect circulating cancer DNA or other genetic markers have been developed or are in development. They are not primary screening strategies because their efficacy for reducing CRC mortality in a general screening population is uncertain [65]. However, the FDA has approved one of these for cancer detection (eg, Shield), and it is an option for individuals who are unwilling or unable to do other types of CRC screening. These tests are discussed separately. (See "Tests for screening for colorectal cancer", section on 'Blood tests'.)
●Multitarget stool RNA tests – Although one stool test for RNA (ColoSense) has been approved by the FDA for CRC screening, it has not yet been included in guidelines. (See "Tests for screening for colorectal cancer", section on 'Multitarget stool RNA tests'.)
●CEA – CEA is a tumor marker that may be used for surveillance of patients with CRC but is not useful for CRC screening. (See "Clinical presentation, diagnosis, and staging of colorectal cancer", section on 'Tumor markers'.)
Resource-limited settings — An ASCO guideline, developed by a multinational panel, stratifies recommended and alternative CRC screening tests for average-risk patients aged 50 to 75 according to availability of clinical resources in the patient's setting [54,55].
●In a basic setting, highly sensitive gFOBT is recommended every one (preferred) to two years, with FIT as a suggested alternative every one (preferred) to two years.
●In a limited setting with more resources, recommended tests include highly sensitive gFOBT yearly or sigmoidoscopy every five years with suggested alternatives of FIT yearly or sigmoidoscopy every 10 years plus yearly FIT (preferred) or yearly FOBT.
FOLLOW-UP OF ABNORMAL RESULTS —
Screening should be supported by a program that assures prompt follow-up of abnormal findings as well as ongoing screening. Patients with an incomplete screening test that did not demonstrate an abnormal finding should have the screening test repeated; this is described separately. (See "Tests for screening for colorectal cancer", section on 'Follow-up of inadequate testing'.)
A patient with any positive (ie, abnormal) screening test for CRC other than colonoscopy itself requires a timely colonoscopy to evaluate for colon polyps and CRC [4,5]. If a stool-based test (fecal immunochemical test [FIT], guaiac-based fecal occult blood test [gFOBT], or FIT-DNA multitarget stool DNA [mt-sDNA] testing) is positive, a second stool test should not be done instead of a follow-up colonoscopy, because a subsequent negative stool test result does not mean that the first result was a false positive. Due to 2023 changes to CMS coverage, a follow-up colonoscopy after a positive noninvasive stool based test is now considered part of a continuum of complete CRC screening, and patient cost-sharing does not apply [66]. If the patient has gastrointestinal symptoms or signs (eg, iron deficiency anemia) suggestive of CRC, a diagnostic evaluation of the entire colon is indicated, even if a previous noninvasive test was negative. (See "Evaluation of occult gastrointestinal bleeding", section on 'Evaluation of a positive fecal occult blood test'.)
Performing the colonoscopy promptly and within three months is advised. Prompt follow-up colonoscopy minimizes the potential for progression of a preclinical lesion to a less curable stage due to a delay in follow-up testing [67,68]. In a retrospective cohort of >70,000 patients aged 50 to 70 who had a positive FIT between 2010 and 2014, rates of detection of any CRC or advanced CRC increased with increasing intervals between FIT and colonoscopy [69]. We therefore do not recommend screening patients if there is no access to colonoscopy if the test is positive.
The further evaluation and management of patients with colonoscopy-detected CRC and polyps are described separately. (See "Clinical presentation, diagnosis, and staging of colorectal cancer" and "Overview of colon polyps".)
When a screening FIT, gFOBT, or mt-sDNA stool test is positive and colonoscopy is both complete (to the cecum with adequate bowel preparation) and without abnormality, patients should return to the routine screening colonoscopy schedule.
While some clinicians may be concerned that a positive mt-sDNA test in the setting of a normal colonoscopy may represent a true rather than a false positive, the available data suggest that such patients do not have a higher risk of cancer than the general population [70]. While this suggests that returning to the routine screening schedule is reasonable for patients with an apparent false-positive mt-sDNA test, larger studies with longer follow-up are needed to confirm these findings.
SOCIETY GUIDELINE LINKS —
Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Screening for colorectal cancer".)
INFORMATION FOR PATIENTS —
UpToDate offers two types of patient education materials, "The Basics" and "Beyond the Basics." The Basics patient education pieces are written in plain language, at the 5th to 6th grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are written at the 10th to 12th grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon.
Here are the patient education articles that are relevant to this topic. We encourage you to print or e-mail these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on "patient info" and the keyword(s) of interest.)
●Basics topic (see "Patient education: Colon and rectal cancer screening (The Basics)")
●Beyond the Basics topics (see "Patient education: Screening for colorectal cancer (Beyond the Basics)" and "Patient education: Colonoscopy (Beyond the Basics)" and "Patient education: Flexible sigmoidoscopy (Beyond the Basics)")
SUMMARY AND RECOMMENDATIONS
●Screening rationale – Screening for colorectal cancer (CRC) can identify premalignant lesions and detect asymptomatic earlier-stage malignancies that have a greater chance of being cured. Screening has been shown to decrease mortality from CRC, and organized screening has been shown to reduce disparities; most of the risks of CRC screening are due to the risks of colonoscopy. (See 'Natural history of colorectal cancer and colon polyps' above and 'Benefits of screening' above and 'Harms associated with screening' above.)
●Assessing risk – We do an initial risk assessment to determine if a patient is at increased risk for CRC at a first office visit and update the information at a minimum of every five years. Patients at sufficiently increased risk to change screening recommendations (eg, start screening at an earlier age and/or perform screening more frequently) include those with a personal or family history of CRC or advanced adenomatous polyp and other risk factors. (See 'Assessing risk for colorectal cancer' above.)
●Age to initiate and discontinue screening
•In patients ages 45 to 49 years, we suggest screening for CRC (Grade 2B). We initiate screening at age 45 years in most average-risk adults to balance the benefits of detection and prevention with the burden on the patient and the risk of harms from screening. In individuals ages 45 to 49, the net benefit of CRC screening is likely moderate; however, it is less well established than in individuals ages 50 to 75. (See 'Age to initiate screening' above.)
•In patients ages 50 to 75, we suggest screening for CRC (Grade 2A). We continue to screen for CRC through age 75 years for average-risk patients, as long as their life expectancy is 10 years or greater. Screening at least until age 75 years for patients at average risk for CRC is recommended by most guidelines.
•For patients aged 76 to 85 years who have been screened before, we individualize the decision about whether to continue screening, based on factors including the patient's preferences, prior testing results, and comorbidities. Screening until age 86 may be reasonable for patients who have never been screened, depending on their comorbidities. (See 'Discontinuing screening' above.)
●Discussing screening tests with patients – After determining that a patient is at average risk for CRC, we discuss specific CRC screening strategies and elicit the patient's preferences regarding them. Key factors that may influence screening decisions for individual patients include the patient's values and overall health status and test efficacy, frequency, safety, availability, convenience, comfort, and cost. (See 'Test selection' above.)
●Test selection – In patients at average risk for CRC, we suggest screening with either colonoscopy or fecal immunochemical testing (FIT), rather than other test options (Grade 2C). This approach is based on the quality of evidence regarding different test options and considerations of test accuracy, convenience, and acceptability. However, because test adherence is essential to the success of screening, other screening tests are reasonable options. These include multitarget stool DNA (mt-sDNA) testing (Cologuard), CT colonography (CTC), high-sensitivity stool guaiac (such as Hemoccult SENSA), or flexible sigmoidoscopy. (See 'Test selection' above.)
●Test frequency – Guideline-recommended CRC screening strategies appear similarly efficacious in reducing death from CRC. However, the frequency of testing and the sensitivity and specificity for the detection of polyps and of CRC vary (figure 1).
•For patients who prefer colonoscopy, we perform it every 10 years. For patients who prefer noninvasive testing or in areas where access to colonoscopy is limited, we typically offer screening by FIT for occult blood annually on a single sample. Comparable alternatives include mt-sDNA testing every one to three years or CTC every five years. (See 'Test options' above.)
•In discussing strategies other than colonoscopy, we emphasize that if the other test result is positive, colonoscopy needs to be performed promptly. (See 'Test options' above.)
•Other tests available for CRC screening include sigmoidoscopy with FIT or with guaiac-based fecal occult blood testing (gFOBT), sigmoidoscopy alone, gFOBT alone, and capsule colonoscopy. (See 'Test options' above.)
●Tests we do not recommend
•Multitarget stool RNA (ColoSense) and some blood-based tests (eg, Shield) have been approved by the US Food and Drug Administration, but we typically do not use them because the data regarding their efficacy are not robust. (See 'Tests that are not recommended' above and "Tests for screening for colorectal cancer", section on 'Blood tests'.)
•CRC screening should not be based on an office-based gFOBT performed following a digital rectal examination. Barium enema tests are no longer recommended for screening because other tests are more effective. (See 'Tests that are not recommended' above.)
●Follow-up of abnormal results – Every positive CRC screening test other than colonoscopy should be followed expeditiously by a colonoscopy to visualize the entire colon for potential lesions. (See 'Follow-up of abnormal results' above.)
ACKNOWLEDGMENTS
The UpToDate editorial staff acknowledges Robert H Fletcher, MD, MSc, who contributed to earlier versions of this topic review.
The author, Dr. Chyke Doubeni, was a member of the United States Preventive Services Task Force (USPSTF). This topic review does not necessarily represent the views and policies of the USPSTF.
