The impact of colonoscopy for colorectal cancer screening

Background

Colorectal cancer is the second leading cause of cancer-related death. Prevention of this neoplasm should be achievable by screening programs in asymptomatic patients. The objective of the present paper is to assess colonoscopic findings in asymptomatic people submitted to screening.

Methods

A prospective study was undertaken on 153 consecutive asymptomatic people submitted to colonoscopy. Sex, age, previous diseases, and familial cases of cancer, as well as tobacco and alcohol ingestion were assessed. Patients with rectal macro- or microscopic bleeding and colorectal diseases were excluded. Bowel cleansing, polyps, angioectasias, diverticular disease, inflammation, and neoplasm were also verified. Polyps were classified according to their size, number, and location.

Results

Colonoscopic alterations were detected in 99 individuals: polyps in 64.3?%, diverticular disease in 27.9?%, inflammatory mucosal alterations in 9.7?%, melanosis coli in 2.6?%, and angioectasias in 7.8?%. There was an increasing incidence of polyps in individuals older than 50?years. Multivariate logistic regression showed age and sex as predictive factors for polyps [odds ratio (OR)?=?1.43; 1.19?<?OR?<?2.67].

Conclusions

The results of this investigation revealed a significant incidence of colonoscopic alterations in asymptomatic people submitted to colonoscopy for colorectal cancer screening.     

Fecal occult blood screening for colorectal cancer in a Veterans Administration hospital

Over a 3.5 year period beginning September 1978, we gave fecal occult blood test kits to 13,522 outpatient applicants for medical care. Two thousand nine hundred sixty-four (22 percent) kits were returned completed according to instructions. One or more specimens were positive in 135 (5 percent) of the tests returned. One hundred twenty of the 135 patients with positive results were investigated by history, physical examination, digital rectal examination, and colonoscopy. Seventy-six of the 120 also had double-contrast barium enemas. Fifty-nine (48 percent) of the 120 patients who completed the work-up had neoplastic lesions; 14 of them were malignant (11.4 percent) and 44 were benign (36.6 percent). Three of the malignant lesions were carcinoma in situ, three had stalk invasion but no residual tumor was found at surgery (Dukes' type A), four were Dukes' type B, and three were Dukes' type C. The classification of one was uncertain. There was stalk invasion, but no further surgery was performed. Thus, of the 14 malignant lesions detected during the first screening, 13 had known classifications and 10 of these 13 were therapeutically favorable (carcinoma in situ, Dukes' type A or B). Ten of the 14 malignant lesions were beyond the range of the rigid proctosigmoidoscope.Our results to date indicate the following: (1) There was excellent patient follow-up and compliance for diagnostic procedures and therapeutic intervention (88.8 percent) when the results of the fecal occult blood test were positive. (2) Neoplasia had a high predictive value (48 percent). (3) A favorable staging for malignant lesions was detected by this method (71 percent). (4) An unacceptably high percentage of malignant lesions were beyond the range of the rigid sigmoidoscope (71 percent). (5) Work-up for patients with a positive fecal occult blood test result should include full colonoscopic examination.     

Faecal occult blood screening for colorectal neoplasia: a randomized trial of three days or six days of tests

Haemoccult, a guaiac test for faecal occult blood, detects 56-78 per cent of asymptomatic carcinomas when performed over 3 days. In patients with known colorectal cancer the sensitivity of the test for neoplasia is increased by extending the test period to 6 days. We report the first randomized comparison of 3 day with 6 day testing in asymptomatic individuals. 35,184 age and sex matched individuals were randomly allocated to receive Haemoccult over 3 or 6 days. The tests were completed by 10,176 (57.8 per cent) of the 17,616 offered 3 day Haemoccult and 9461 (53.9 per cent) of the 17,568 offered 6 day Haemoccult, a significant decrease in compliance (P less than 0.001). Of the 3 day Haemoccult tests 131 (1.29 per cent) were positive, significantly fewer than the 160 (1.69 per cent) positive tests after 6 day Haemoccult (0.01 less than P less than 0.02). Investigation of subjects with a positive test revealed 20 carcinomas (1.14 per 1000 offered and 1.97 per 1000 completing the test) in the 3 day group and 24 carcinomas (1.37 per 1000 offered and 2.54 per 1000 completing the test) after 6 day Haemoccult tests (0.5 less than P less than 0.7 for those offered the test and 0.3 less than P less than 0.5 for those completing it). After 3 day Haemoccult 112 adenomas in 76 persons were detected (4.31 per 1000 offered and 7.47 per 1000 completing the test). In the 6 day group 123 adenomas in 83 persons (4.72 per 1000 offered and 8.77 per 1000 completing the test) were detected (0.5 less than P less than 0.7 for those offered the test and 0.3 less than P less than 0.5 for those completing it). Large adenomas were found in 27 individuals after 3 day testing (1.53 per 1000 offered the test and 2.65 per 1000 completing it) and in 35 individuals after 6 day testing (1.99 per 1000 offered the test and 3.70 per 1000 completing it) (0.3 less than P less than 0.5 for those offered the test and 0.1 less than P less than 0.2 for those completing it). This study has not demonstrated a significant increase in the yield of neoplasia in asymptomatic subjects offered Haemoccult over 6 days. However there was a significant decrease in compliance and a higher rate of colonscopy in those offered 6 day testing.     

Colorectal cancer screening: optimal compliance with postal faecal occult blood test.

Five approaches to postal faecal occult blood test (FOBT) were compared in a population sample of 966 subjects collected from three general practitioner patient lists in Southern Sydney. The highest compliance rate (59.8%) was achieved by a method using a general practitioner letter, with no dietary restrictions with FOBT. This was also the least expensive method. Compliance rates can be affected by incorrect address information and screenees not considering themselves to be current patients. An explanation from the family doctor addressed personally to the patient with an enclosed FOBT kit can achieve high compliance rates.     

A population‐based audit of the clinical use of faecal occult blood testing in primary care for colorectal cancer

Aim Symptoms related to colorectal cancer (CRC) are common. We investigated the value of the faecal occult blood test (FOBT), when administered in primary care, in the diagnosis of CRC. Method All patients who underwent a FOBT (Hemoccult II) at 20 public primary care centres in Sörmland County, Sweden, during 2000–2005, were included (n = 9048). Linkage to the Swedish Cancer Registry identified all cases of CRC. Symptoms recorded at the time of the FOBT were retrieved from the patient records. The outcome from the FOBT to diagnosis and subsequent survival was compared between patients who were FOBT negative and patients who were FOBT positive. Results One‐hundred and sixty‐one patients were diagnosed with CRC within 2 years after undergoing a FOBT in primary care. These comprised 18% of all 917 patients diagnosed with CRC in the county during the study period. In 41 (25.4%) of the 161 patients the test was negative. Symptoms related to CRC were documented for 158 (98%) patients at the time the FOBT was administered. The median investigation time from the FOBT test to the diagnosis of CRC was 91 days: 80 days for FOBT‐positive patients and 188 days for FOBT‐negative patients (P < 0.001). This difference was signficant independent of age, sex and site of tumour. The hazard ratio for FOBT negativity, 3 years after the FOBT, when adjusted for age and sex, was 1.47 (95% CI, 0.81–2.68). Conclusion Despite having suggestive symptoms, 41 (4.5%) of 917 CRC patients had a negative FOBT result in primary care. This was associated with diagnostic delay and, potentially, a worse outcome.     

Effectiveness of a colonoscopic screening programme in first‐degree relatives of patients with colorectal cancer

Aim The study aimed to assess the diagnostic yield of a colonoscopy screening programme in first‐degree relatives of colorectal cancer (CRC) patients and to identify factors associated with advanced neoplasia. Method We conducted a cross‐sectional study. Individual characteristics, family trees and colonoscopy findings of asymptomatic first‐degree relatives of CRC patients were collected. The findings were classified into cancer (invasive carcinoma and/or non‐invasive high‐grade neoplasia), high‐risk adenomas (≥ 10 mm and/or a villous component) and low‐risk adenomas (tubular < 10 mm). The dependent variable was the presence of advanced neoplasia, defined as cancer and/or high‐risk adenoma. Results Two hundred and sixty‐three relatives (147 females), 50.0 ± 11.5 (range, 25–75) years of age, agreed to participate out of a total of 618 who were invited (acceptance rate 42.5%). Index cases were diagnosed at 63.8 ± 12.4 (range, 37–88) years of age. The closest familial relationship was parent/offspring in 168 (63.9%) participants and sibling in 95 (36.1%) participants; 14.8% had three or more relatives with CRC/cancer associated with Lynch syndrome, and two or more affected generations were identified in 24.0%. Advanced neoplasia was found in 56 (21.3%) participants. Of these, invasive cancer, non‐invasive high‐grade neoplasia and high‐risk adenomas were detected in five (1.9%), six (2.3%) and 45 (17.1%) participants, respectively. Low‐risk adenomas were detected in 20 (7.6%) participants. Male sex (odds ratio, 2.59; P = 0.003) and sibling relationship (odds ratio, 2.74; P = 0.001) were independently associated with advanced neoplasia. Conclusion We detected advanced neoplasia in a considerable number of participants. Our data support colonoscopy screening in first‐degree relatives of patients with CRC at an earlier age than in the medium‐risk population. Male sex and sibling relationship were predictors of advanced neoplasia.     

Evaluation of an immunochemical test for faecal occult blood in screening for colorectal neoplasia in a high risk group

A group of 1615 asymptomatic individuals presumed to be at increased risk of colorectal neoplasia were selected as the study group. All were tested by an immunochemical test for faecal occult blood. In the second half of the study, individuals who were occult blood negative were offered colonoscopy. Ninety-nine individuals (6.1%) returned stools which were occult blood positive. Investigation by full colonoscopy was possible in 90 cases, revealing nine patients (10%) with invasive cancers, four patients (4.4%) with carcinomata in situ, and 36 patients (40%) with adenomata. Non-neoplastic pathology capable of producing occult blood positive stools was found in 31 individuals (34.4%). No pathology was found in 10 instances (11.1%). Of the 53 occult blood negative subjects who underwent colonoscopy, eight were found to have adenomata. Only one of these was larger than 5 mm in diameter (18 mm). No carcinomata were found. The site within the large bowel of the tumour did not appear to significantly affect the occult blood status of the faeces but the size of the tumours detected suggests that the presence of blood within the stool is more likely to be associated with larger lesions. The frequency of detection of both carcinomata and adenomata was greatest in individuals who had a past history of colorectal neoplasia. The individual cost of this immunochemical test is nominal. The high diagnostic yield and low false positive and negative rates suggest that case follow-up, surveillance, or screening utilizing this test is justified.     

湖北地区目标人群中大肠癌筛检结果分析

目的通过大肠肿瘤序贯隐血筛检方案的实施,了解湖北地区大肠癌的患病率,并对该方案的应用进行分析。方法采用随机整群分层抽样,选取5个筛查点的17418人作为目标人群,对其中40岁以上者进行序贯粪隐血试验,对阳性者进一步行肠镜检查;并对符合条件的高危人群进行粪隐血和肠镜检查。结果目标人群17418人,40岁以上者8884人,接受粪隐血试验检查者2908人。男女比例1：1.1,中位年龄52岁。序贯粪隐血试验阳性者316人,阳性率为10.9%。序贯粪隐血试验阳性者中124人接受肠镜检查。检出大肠癌5例,检出率1.6%。Dukes A期和B期4例,占检出大肠癌的4/5。结论湖北地区大肠癌的患病率呈较高水平,序贯粪隐血筛检方案有较高的有效性和可行性,尤其是在大肠癌的早期防治中。提高受检人群的依从性是未来筛检工作的重点。     

Survival of patients with colorectal cancer diagnosed in a randomized controlled trial of faecal occult blood screening.

BACKGROUND: Analysis of survival of subjects with colorectal cancer diagnosed by different modalities can provide insight into the mechanism by which screening has an effect. It can also give an indication of the feasibility of using prognostic indicators as surrogate outcome measures to predict mortality in future studies. METHODS: This paper examines the survival of individuals with colorectal cancer diagnosed in the Nottingham trial and explores the role of selected prognostic factors as possible surrogate outcome measures. RESULTS: Survival was significantly better in subjects with screen-detected cancers than in controls, even after adjusting for tumour stage and accounting for lead-time bias. Survival was inversely related to stage of tumour, with patients with stage A tumours having the best survival. Subjects with well or moderately differentiated tumours had a significantly better survival than those with poorly differentiated tumours. CONCLUSION: Screening for colorectal cancer by means of faecal occult blood testing improved survival among subjects with screen-detected cancers. Differences in prognostic factors largely explain the differences in survival between both non-responders and subjects with interval cancers and those in the control group, but not the improved prognosis for patients with screen-detected cancers. The use of such factors as surrogate outcome measures may therefore be inappropriate.