4. Screening Asymptomatic Population – Colorectal Cancer
Asymptomatic Population – Definition:
Persons who do not belong to a colorectal cancer risk group.
4.1 Screening - Age
Colorectal cancer screening should begin at the age of 50 for asymptomatic persons. Due to the increased life expectancy, no upper age limit for screening can be given for colon cancer screening. An individual decision should be made considering comorbidities.
- Consensus
- Strong consensus
Background
The incidence of CRC increases significantly after age 50 [92][93]. A prospective colonoscopy study showed that there was a lower rate of advanced adenomas among 40 to 49 year old subjects (3.5%) [94]. Of great importance is the identification of persons with an increased risk of CRC, for whom special recommendations apply (see Chapter 5).
There are no prospective studies concerning an age limit for colorectal cancer screening. FOBT-studies included only persons up to age 75. The US Preventive Task Force discourages screening persons over 85 years of age and generally recommends that screening should not be done in persons age 76 to 85 years [95]. However, it may be considered for individual cases. The incidence of advancing neoplasias increases with age [96]. Performing endoscopic procedures also seems to be safe in older patients [97]. However, in a cohort study the complication rate increased with age [98]. In another study the relative five-year survival rate after curative operations of colorectal cancer for patients over 74 years of age were comparable with patients aged 50 to 74 [99]. Therefore, the use of CRC screening should be considered individually depending on "biological age" and existing comorbidities. There are insufficient data on the benefit/risk ratio for colorectal cancer screening in different age groups.
4.2 Methods of Colorectal Screening/Prevention
Two types of methods must be differentiated for the screening of CRC. One detects mainly cancer (FOBT, genetic stool tests, M2-PK) and the other can additionally detect adenomas (colonoscopy, sigmoidoscopy, CT-colonography, capsule endoscopy). The following procedures will be discussed:
- Colonoscopy
- Sigmoidoscopy
- FOBT
- Genetic and other stool tests
- CT-colonography
- Capsule endoscopy
4.2.1 Endoscopic Methods
Colonoscopy has the highest sensitivity and specificity of all methods for the early detection of colorectal neoplasia (therefore it is considered as ‘gold standard’). Only endoscopic methods are diagnostic as well as therapeutic methods and have the advantage that they can detect non-bleeding cancer and adenomas with high sensitivity. By removing adenomas, the development of cancer can be effectively prevented (interruption of the adenoma-carcinoma sequence) [205][206]. In addition, as was recently demonstrated, the CRC-associated mortality is reduced [Zauber, A. G. et al. 2012].
Although the participation rate was low compared to FOBT, individual randomized studies showed that in an intention to screen analysis both sigmoidoscopies [134] and colonoscopies [Quintero, E. et al. 2012] detect more advanced neoplasias. This was particularly due to the clearly higher sensitivity for advanced adenomas.
4.2.1.1 Colonoscopy
The complete quality assured colonoscopy has the highest sensitivity and specificity for the detection of cancer and adenomas and therefore should, be used as the standard CRC screening test. After a negative examination, colonoscopies should be repeated every 10 years. Colonoscopies should be performed according to the German Prevention Guidelines [3] including a digital rectal examination. For those taking part in colonoscopy screening according to the guideline additional FOBT screening is not necessary.
Background
In contrast to FOBT and sigmoidoscopy no results from randomized studies exist for CRC screening and prevention. Such studies have been initiated in Europe and the US. However, results are expected at the earliest in 15 years. Nonetheless, the use of colonoscopy is supported by indirect evidence. An external literature search identified a study from Germany. In this study patients with a CRC diagnosed by screening colonoscopy had a better prognostis than patients who had a colonoscopy because of symptoms [100]. Another US trial demonstrated that a cohort of 715 persons who had screening colonoscopies had a significantly reduced CRC-associated mortality and incidence compared to the control collective [101].
Large cohorts including from Germany showed colonoscopies can detect a large number of cancer at an early stage as well as adenomas in the whole colon [98]. In Germany, about 1/3 of the detected cancer in screening colonoscopies are located proximal to the colon descendens [98]. In further studies, 46 to 52% of patients with proximal neoplasias had no additional distal adenomas [102][103]. A diagnosis of neoplasias using sigmoidoscopy would have been impossible in these patients.
The results of the sigmoidoscopy case-control studies and the randomized UK study on sigmoidoscopy which both show reduction of cancer incidence and mortality should be transferable to colonoscopy [104][105][106][107]. However, the effect in the proximal colon seems to be smaller than in the distal colon [108][109][110]. The protective effect shown in FOBT studies ultimately results from performing colonoscopies in patients with positive tests.
The colonoscopy complication rate in a German study with volunteers was very low [111]. These results have recently been confirmed [98]. However, it is likely that not all complications were detected, because late complications were only incompletely recorded. Tandem examinations showed that larger adenomas were seldom missed (0- 6%) [112].
If a colonoscopy is negative, it should be repeated after 10 years. Colonoscopies performed 5.5 years after negative endoscopy results, showed no cancer and less than 1% advanced neoplasias [113]. Case control studies indicate that after a negative colonoscopy the cancer risk remains very low even after more than 10 years [108][114].
It is very important that the colonoscopy is performed with the best possible quality. In Germany, there are clear guidelines for performing colonoscopies [116].
4.2.1.2 Sigmoidoscopy
Quality assured sigmoidoscopies should be offered as a screening measure to those who refuse a colonoscopy.
- Recommendation grade
- B: Empfehlung für oder gegen eine Maßnahme - verwendete Ausdrucksweise = sollte/sollte nicht
- Level of evidence
- 2b
- Consensus
- Strong consensus
- References
- [117]
For the possible detection of proximal cancer, an annual FOBT test should be performed in addition to a sigmoidoscopy.
Background
The effectiveness of sigmoidoscopy as a screening method for CRC has been proven. An English randomized study comparing a single sigmoidoscopy to no screening after a follow-up of 11.2 years, showed that the CRC associated mortality was reduced by 43 % and the incidence of colorectal cancer by 33 % [117]. The incidence of distal cancer was 50 % lower.
However, it should be taken into consideration that not all sections of the colon can be viewed using sigmoidoscopies. In accordance, a sigmoidoscopy study showed that the incidence of proximal cancer was not affected. In this case colonoscopies are superior to sigmoidoscopies.
The protective effect of sigmoidoscopies for distal neoplasias appears to last for 6 to 10 years [107][118], and in one study even as long as 16 years [119]. However, a study with 9,417 subjects who underwent a sigmoidoscopy 3 years after a negative one showed advanced adenoma or cancer in the distal colon in 0.8% of the cases [120]. Another study in 2,146 participants with negative sigmoidoscopies compared screening/follow-up intervals of 3 and 5 years [121]. The rate of advanced neoplasias did not differ significantly (0.9% vs. 1.1%). Thus, a follow-up exam after a negative result is recommended after 5 years.
Because proximal tumors cannot be detected with a sigmoidoscopy, an additional annual FOBT is recommended. It should be performed before sigmoidoscopy, because a positive test requires a colonoscopy and, thus, an additional sigmoidoscopy can be avoided. However, a reduction of CRC-related mortality using a combination of sigmoidoscopy and FOBT has not yet been proven. A prospective non-randomized study found a lower CRC-related mortality for the combination, but the results failed to meet the test for significance and the compliance was exceptionally low [122]. In several studies, however, a combination of sigmoidoscopy and one-time FOBT was not significantly better than sigmoidoscopy alone [123][124]. In the most recent study from Japan, a combination of sigmoidoscopy and FIT detected 10% (absolute) more advanced neoplasias [125].
However, it should be considered that currently in Germany sigmoidoscopies are not covered by the health insurance catalogue of benefits and, thus, they cannot be charged. Furthermore, in contrast to screening colonoscopies no quality assurance measures are established for sigmoidoscopies. In England, a requirement for the participation in a sigmoidoscopy study was at least 50 supervised and 100 independent sigmoidoscopies [104]. Every examination was documented on video. The colon depth that was reached, the quality of colon preparation, and the results were recorded.
4.2.1.3 Capsule-Colonoscopy
Capsule colonoscopy should not be used for colon cancer screening in the asymptomatic population.
Background
A literature search on capsule colonoscopy for screening did not identify any studies. There are a number of case series on sensitivity and specificity of colorectal neoplasias using the first capsule generation [126][127][128][129][130]. For the second capsule generation (PCC2) with improved technical characteristics, a sensitivity of 84-89% was reported for polyps larger than 6 mm [131][132]. However, this was a small cohort with preselected patients so that currently its use for colorectal cancer screening cannot be recommended for the general population.
4.2.2 Stool Tests [4]
[4]: Prof. Schmiegel did not take part in the votes on the recommendations concerning FOBT/iFOBT, genetic stool tests and M2-PK because of a potential conflict of interest.
4.2.2.1 Fecal Occult Blood Test (FOBT)
For persons with an average CRC-risk who do not want a colonoscopy, a FOBT should be conducted annually.
- Consensus
- Strong consensus
A positive test result requires endoscopic examination of the entire colon.
- Level of evidence
- 1a
- Consensus
- Strong consensus
Annual FOBTs are better to reduce CRC-associated mortality than testing once every two years.
- Level of evidence
- 1b
- Consensus
- Strong consensus
- References
- [133]
Immunologic FOBTs (iFOBT) with a proven high specificity of >90% and sensitivity may be used alternatively to the Guaiac test.
Background
The basic principle of stool testing for occult blood is that colorectal cancer bleed more often than normal colorectal mucosa. Traditional FOBTs use filter paper impregnated with Guaiac resin which after adding hydrogen peroxide turns blue in the presence of hemoglobin in the stool. In Germany, there are currently three Guaiac tests available: Hemoccult®, HemoCare®, and HemoFEC®. The most sensitive gFOBT (Hemoccult Sensa®) is not available in Germany. Because many cancer bleed intermittently [145], repeated testing is required in order to improve detection of CRC [146][147]. Accordingly, in the studies three consecutive stools with 2 samples per stool were tested using test cards with two fields each (i.e. 6 fields total) [148].
The results of four large randomized studies exist on the effectiveness of FOBT as a screening method for colorectal cancer [133][149][150]. In the most recent meta-analysis of these studies, a reduction of CRC-associated mortality by 25% was shown for those patients who had an FOBT at least once (relative risk 0.75, 95%CI 0,66 – 0.84) [151]. In three of the four studies a gFOBT was done every 2 years. When comparing tests every year with tests every two years, the annual testing was better with regard to reduction of mortality [133].
Test sensitivity and specificity are particularly dependent upon test handling and patient instruction. A rehydration of the test fields before their development increases screening sensitivity, but clearly reduces specificity (in one study from 97.6% to 90.2%, in another study from 97 to 85.4% [133][152]) and is, therefore, not recommended. There is evidence that instructing patients before conducting the test on nutrition and interfering drugs can reduce the number of false positive tests and, therefore, the number of necessary colonoscopies [153][154][155]. Therefore, it seems helpful to explain to patients the factors which can influence test results. The influence of plant peroxidases can alternatively be prevented by waiting for 3 days before test development [156]. However, the necessity of dietary restrictions for FOBT was questioned in a meta-analysis [157].
If one test field is positive for occult fecal blood, a complete colonoscopy after digital rectal examination is mandatory. Unfortunately, even under study conditions in some cases less than 90% of all persons with positive FOBT had a colonoscopy [158]. In one study it was even only 64% [159].
The effect of FOBTs on CRC-mortality results from the diagnosis of colorectal cancer at an earlier stage with a more favorable prognosis. Advantages of FOBT include an easy test performance as well as low costs. A disadvantage is the moderate sensitivity for cancer and the low sensitivity for adenomas. In one randomized study a reduction in colorectal cancer incidence was shown; it must be considered, however, that in the context of this study over 30% of the participants underwent a colonoscopy [160].
Immunological tests specifically detect human hemoglobin. Thus, no change in diet is necessary during testing. In contrast to the gFOBT, some tests also have the option of automated analysis and changing the hemoglobin threshold values which would be considered positive. Tests are either called immunologic FOBT (iFOBT) or fecal immunochemical tests (FIT). Currently in Germany, they are not covered by health insurance. In contrast to the gFOBT, there are no studies with an endpoint of CRC- associated mortality reduction. However, there are a number of randomized studies which compare individual iFOBTs directly with certain gFOBTs. In a meta-analysis of these studies identified in a literature search individual iFOBTs (OC-Sensor)) were significantly better at detecting advanced neoplasia than the Hemoccult® test (pooled odds ratio (OR) of 2.12 (95% CI 1.66–2.71) [135]. In two studies which compared the gFOBT HemoFEC® or Hemoccult Sensa® with an iFOBT (Inform® or FlexSure®), however, no significant difference was found [135]. In particular, in the two largest randomized studies from The Netherlands [134][136] a significant difference was found suggesting a superiorbity of the iFOBT used (OC-Sensor) over the Hemoccult.
Sensitivity and specificity of iFOBT available in Germany vary greatly so that the general use of iFOBTs is not recommended [137]. It seems necessary to prove a sufficient sensitivity and especially the specificity individually for each iFOBT that will be used for screening. The lowest acceptable specificity limit is considered to be 90%. The results of screening studies suggest that, if a corresponding cut-off is adjusted, a similarly high specificity of >90% as for the gFOBTs can be reached for the iFOBT with much higher sensitivity [138][144]. Currently, the optimal hemoglobin content at which the iFOBT should be considered positive is under discussion. In both Dutch publications the limit was 100 ng/ml. In the included studies one stool sample each was examined using the iFOBT. Some data show that the testing of several stool samples increases its sensitivity [140][141][142]. However, a trial from The Netherlands shows that reducing the cut-off has a similar effect [143]
Overall the data show that iFOBT, for which there are appropriate data, are a useful substitute for gFOBT.
For those who take part in colonoscopy screening, there is no need for any additional FOBT or other screening tests.
- Level of evidence
- 1a
- Consensus
- Strong consensus
4.2.2.2 Genetic Screening Tests
Stool tests that measure DNA changes cannot be recommended for CRC screening in the asymptomatic population.
Background
In many cases, the development of colorectal cancer through the intermediate step of the adenoma takes place with characteristic genetic changes. Isolation and testing of DNA from colon epithelial cells in the stool is possible [161][162][163][164]. This procedure has the advantage that theoretically non-bleeding lesions could also be identified. In a study by Imperiale which included almost 5,500 asymptomatic persons, stool samples of 2,500 participants were tested for a total of 23 genetic variants. They were then compared to the gFOBT [165]. The sensitivity of the genetic tests was higher than for the gFOBT. However, it was merely 50% for cancer and 15% for advanced adenomas with costs of several hundred US Dollars per test and a tedious procedure. A literature search identified only one other study [166]. In this prospective study 3,764 asymptomatic persons aged 50 to 80 years had a gFOBT and a colonoscopy. Of these, 2,497 participants had stool samples tested with a DNA-panel I with the same markers as in the Imperiale study and 217 with a DNA-panel II with only 3 mutations including the methylation marker vimentin. The sensitivity for relevant neoplasias was 20% for DNA- panel I and 40% for DNA-panel II. The sensitivity for the Hemoccult®-test was 11%, for the Hemoccult-Sensa® 21%. The specificity for the DNA-panel II was not determined. Overall panel I was better than one of the gFOBTs (Hemoccult®) and equal to the other gFOBT (HemoccultSensa®). Panel II seemed to be better than both gFOBT. However, it was only tested in a small proportion of the participants.
In summary, the data and results are not sufficient when considering the effort and costs of each test. Therefore, they can currently not be recommended.
4.2.2.3 M2-PK
Background
The majority of studies were done on preselected patient collectives. Thus, no conclusion can be made on the relevance of the test for screening the asymptomatic population. In externally performed literature searches two studies were identified on analyzing screening populations [167][168]. One study compared the M2-PK test with colonoscopies in 1082 asymptomatic persons. The sensitivity for advanced adenomas was 21.7% with a specificity of 82%. Another study including 1,079 participants compared the M2-PK test with different FOBT. The sensitivity for advanced neoplasia was 27.3% (compared to 7.3-20.0% for the FOBT) and a specificity of 86.2% (FOBT 92.9- 94.0%). The positive predictive value for advanced neoplasia was 11.5% and lower than all FOBTs tested. Overall, the data are not sufficient to recommend the test for the screening of the asymptomatic population.
4.2.3 Radiologic Tests
Neither CT-colonography nor MR-colonography should be used for colon cancer screening in the asymptomatic population.
In case of an incomplete colonoscopy (e.g. adhesions) und if the patient still insists on complete colon analysis a CT- or MR-colonography should be done.
Background
For the use of MR-colonography there are only individual small studies which do not provide enough data to recommend its use for screening. More data are available for CT- colonography (CTC). The two most current meta-analyses identified in the literature search comparing CTC with colonoscopy as screening procedures in the asymptomatic population showed a high sensitivity of 100 % detection for cancer and 87.9 % for adenomas ≥ 10 mm. The sensitivity for smaller adenomas was not as high [169][170]. Furthermore, there is significant heterogeneity between the different studies. It remains unknown whether the study results that were attained at experienced centers are applicable to clinical practice. Also the relevance of extracolonic results is unclear. The method involves radiation exposure, which in Germany is prohibited according to the Radiation Protection Ordinance (StrlSchV §80). Thus, it is not allowed if alternative methods are available. The exact neoplasia risk due to CTC using modern equipment with reduced radiation dose is not known. It is also unclear which polyp size mandates a colonoscopy and in which interval patients with negative CTC or smaller polyps should be monitored [171].
Patients who had an incomplete colonoscopy for technical reasons should be offered to repeat the procedure e.g. in a hospital or to have a CTC as an alternative to analyze the rest of the colon (see Chapter 6.1.)
4.3 Cost Effectiveness
FOBT as well as sigmoidoscopy, colonoscopy, and the combination of sigmoidoscopy and FOBT have been shown to be cost-effective (in comparison to screening procedures for other diseases).
- Consensus
- Consent
4.4 Recommendations of Other Included Guidelines
According to the DELBI-criteria 2 guidelines were included for CRC screening, the recommendations of the US Preventive Task Force from 2008 [95] and the Asian Pacific consensus recommendation from 2007 [183]. The US-Preventive Task Force recommends the following methods: a sensitive FOBT (Hemoccult Sensa® and IFOBT/FIT) annually, a sigmoidoscopy every 5 years with an FOBT every 3 years, or a colonoscopy every 10 years. The use of CT-colonography and genetic stool tests is not recommended. Capsule endoscopy and the M2-PK-test are not listed. It should be mentioned that the Hemoccult Sensa® is not available in Germany.
The Asian Pacific guideline recommends a FOBT (gFOBT und iFOBT) every 1-2 years, a sigmoidoscopy every 5 years, and a colonoscopy every 10 years. A CT-colonography is not recommended, and genetic stool tests, capsule endoscopies, and M2-PK-tests are not mentioned.
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