Endoscopic and histologic correlates of colorectal polyp bleeding

Screen-detected colorectal cancers are associated with an improved outcome compared with stage-matched interval cancers

Background:

Colorectal cancers (CRCs) detected through the NHS Bowel Cancer Screening Programme (BCSP) have been shown to have a more favourable outcome compared to non-screen-detected cancers. The aim was to identify whether this was solely due to the earlier stage shift of these cancers, or whether other factors were involved.

Methods:

A combination of a regional CRC registry (Northern Colorectal Cancer Audit Group) and the BCSP database were used to identify screen-detected and interval cancers (diagnosed after a negative faecal occult blood test, before the next screening round), diagnosed between April 2007 and March 2010, within the North East of England. For each Dukes' stage, patient demographics, tumour characteristics, and survival rates were compared between these two groups.

Results:

Overall, 322 screen-detected cancers were compared against 192 interval cancers. Screen-detected Dukes' C and D CRCs had a superior survival rate compared with interval cancers (P=0.014 and P=0.04, respectively). Cox proportional hazards regression showed that Dukes' stage, tumour location, and diagnostic group (HR 0.45, 95% CI 0.29–0.69, P<0.001 for screen-detected CRCs) were all found to have a significant impact on the survival of patients.

Conclusions:

The improved survival of screen-detected over interval cancers for stages C and D suggest that there may be a biological difference in the cancers in each group. Although lead-time bias may have a role, this may be related to a tumour's propensity to bleed and therefore may reflect detection through current screening tests.

Identification of colorectal adenomas by a quantitative immunochemical faecal occult blood screening test depends on adenoma characteristics, development threshold used and number of tests performed

BACKGROUND

Faecal occult blood tests (FOBT) are faulted by low sensitivity for advanced adenomatous polyps (AAP). Quantified, immunochemical, haemoglobin (Hb)-specific immunochemical FOBT (I-FOBT) measurements are now used for colorectal screening.

AIMS

To correlate adenoma characteristics to amount of faecal Hb lost and to evaluate sensitivity and specificity for AAP by faecal Hb development threshold used and number of I-FOBTs collected.

METHODS

Three daily I-FOBTs were collected and analysed in 1221 patients scheduled for colonoscopy. Faecal Hb was analysed as ngHb/mL of buffer and the highest result related to colonoscopy findings.

RESULTS

In 1204 patients without cancer, colonoscopy identified adenomas in 294, 99 with AAPs. Adenoma patients had elevated faecal Hb increasing with advanced histology, size, pedunculated shape and multiplicity (P < 0.001 for all). At 50 ngHb/mL threshold, sensitivity and specificity for AAPs were 54.5% (95%CI 44.7, 64.7) and 88.1% (95%CI 86.2, 90.1) for three tests. At higher thresholds, sensitivity decreased, but was significantly higher with more samples collected. Conversely, specificity increased at higher thresholds, but decreased with more samples.

CONCLUSIONS

Faecal Hb loss from adenomas is significantly associated with size, number and advanced features. Sensitivity and specificity for AAPs are determined by test threshold chosen and number of samples collected; these determine the number of colonoscopies needed for positive tests.

Review article: faecal occult blood testing for colorectal cancer

Major health organizations recommend colorectal cancer screening using faecal occult blood tests, sigmoidoscopy or both for patients 50 years of age or older who are at average risk for colorectal cancer. However, no specific recommendations have been made regarding choice of test from among the tests currently or soon to be available. Therefore, to aid clinicians in rationally choosing a particular test for faecal occult blood, published data are reviewed regarding the performance characteristics, strengths and weaknesses of the various faecal occult blood tests. New studies suggest that immunochemical tests (e.g. HemeSelect) or a combination of sensitive guaiac tests and immunochemical tests (e.g. Hemoccult Sensa and HemeSelect) are the most sensitive, specific tests for detecting colorectal carcinoma and colorectal polyps > or =1 cm.

Detection rate of immunochemical fecal occult blood test for colorectal adenomatous polyps with severe dysplasia

This study was conducted to assess the accuracy of an immunochemical occult blood test for detecting colorectal adenomas with severe dysplasia, and to determine the relationship between the grading of adenomatous dysplasia and the results of this test. Sixteen colorectal adenomas under 1 cm with severe dysplasia, 65 adenomas under 1 cm with mild-to-moderate dysplasia, 65 adenomas 1 cm or larger with mild-to-moderate dysplasia, 65 colorectal cancers and 130 healthy controls were investigated. Each subject was tested with an immunochemical fecal occult blood test on 3 consecutive days, and the accuracy of the test was evaluated. The detection rate of this test was 13% for severe dysplasia under 1 cm, 45% for severe dysplasia 1 cm or more, 17% for mild-to-moderate dysplasia under 1 cm, 40% for mild-to-moderate dysplasia 1 cm or more, and 89% for colorectal cancers, and the false positive rate was 5%, showing a significant difference in the detection rate between severe dysplasias 1 cm or more and those under 1 cm (P < 0.05) as well as significant difference between severe dysplasias 1 cm or more and mild-to-moderate dysplasia under 1 cm (P < 0.01), and between cancers and adenomas (P < 0.001), whereas there was no significant difference between the detection rates for severe dysplasia 1 cm or more and mild-to-moderate dysplasia 1 cm or more. These results indicate that there is no association between the detection rate of this immunochemical occult blood test for adenomas and the grade of adenomatous dysplasia.

Factors that influence bleeding in superficial-type colorectal tumors: study of endoscopic and histologic correlates

To clarify the mechanisms responsible for superficial-type colorectal tumor (STT) bleeding, 74 STTs were studied to determine whether their size, shape, surface area features, colorectal site, and level of invasion were correlated with bleeding. The bleeding rate, the proportion of specimens from patients with positive fecal occult blood test (FOBT) results relative to the total number of specimens in each morphological group and probability of an STT being an invasive submucosal carcinoma were positively correlated with tumor size, and bleeding was more common in submucosal than in intramucosal lesions. Logistic regression analysis indicated that the level of submucosal invasion had a significant influence on bleeding. It was also found that the length of erosion on the surface of STTs was significantly greater in bleeding tumors, and that the potential for invasion into the submucosa increased with the area of erosion.

A comparison of fecal occult-blood tests for colorectal-cancer screening

BACKGROUND

Hemoccult II, a widely used guaiac test for fecal occult blood, has a low sensitivity for detecting colorectal neoplasms in asymptomatic patients at average risk. In such patients, the performance characteristics of screening tests developed to improve on Hemoccult II are not known.

METHODS

A set of three fecal occult-blood tests--Hemoccult II; Hemoccult II Sensa, a more sensitive guaiac test; and HemeSelect, an immunochemical test for human hemoglobin--was mailed to all patients 50 years of age or older who were scheduled for personal health appraisals at the Kaiser Permanente Medical Center in Oakland, California. The performance of each test and of a combination test (HemeSelect to confirm positive Hemoccult II Sensa results) was evaluated by identifying screened patients who had colorectal neoplasma (carcinoma or a polyp > or = 1 cm in diameter) in the two years after screening.

RESULTS

Of the 10,702 eligible patients, 8104 (75.7 percent) had at least one interpretable sample and were screened on the basis of at least one test; 96 percent of these patients had complete two-year follow-up. The sensitivity of the tests for detecting carcinoma was lowest with Hemoccult II (37.1 percent; 95 percent confidence interval, 19.7 to 54.6 percent), intermediate with the combination test (65.6 percent; 95 percent confidence interval, 47.6 to 83.6 percent) and with HemeSelect (68.8 percent; 95 percent confidence interval, 51.1 to 86.4 percent), and highest with Hemoccult II Sensa (79.4 percent; 95 percent confidence interval, 64.3 to 94.5 percent). The specificity for detecting carcinoma was 86.7 percent with Hemoccult II Sensa, 94.4 percent with HemeSelect, 97.3 percent with the combination test, and 97.7 percent with Hemoccult II. HemeSelect and the combination test detected more colorectal carcinomas and polyps than Hemoccult II, with only slight increases in the number of colonoscopies needed.

CONCLUSIONS

HemeSelect and a combination test in which HemeSelect is used to confirm positive Hemoccult II Sensa results improve on Hemoccult II in screening patients for colorectal carcinoma.