Predictive factors by multivariate analysis for colorectal cancer in Malaysian patients undergoing colonoscopy

BACKGROUND: The majority of colorectal cancers are still diagnosed in patients who present with symptoms especially in countries where colorectal screening programs are not practised. The aim of our study was to determine the predictive factors for colorectal cancer in patients referred for colonoscopy. METHODS: A prospective study of 485 consecutive patients who underwent colonoscopy during a 22-month period was performed. All patients answered a detailed questionnaire. Indications for colonoscopy and the findings were recorded. RESULTS: The mean age of the study population was 55.7 +/- 14.7 years. There were 221 (45.6%) males and 264 (54.4%) females. Sixty-five (13.4%) were Malays, 298 (61.4%) were Chinese and 112 (23.1%) were Indians. Multiple backward stepwise regression analysis revealed that independent predictors for colorectal cancer (odds ratio [95% CI]) were the presence of rectal bleeding (4.3 [4.0-8.0]) and iron deficiency anemia (4.0 [3.6-10.2]). In those aged 50 and over, male gender (4.5 [2.2-9.3]) and abdominal pain (3.1 [1.4-6.7]) were also significant positive predictors of cancer. CONCLUSIONS: With the ever-increasing demand for gastrointestinal endoscopy, the appropriate utilization of colonoscopy is essential to afford prompt patient evaluation. Our study supports the need to prioritize the use of colonoscopy in patients with rectal bleeding and iron deficiency anemia. In the older patient where the background prevalence of colorectal cancer is higher, referral for colonoscopy is also justified.     

Open access endoscopy in rural and remote Western Australia: Does it work?

Background: Access to diagnostic endoscopy is limited in rural and remote Western Australia. Published reports suggest open access referrals may result in over‐servicing, this is reduced by adherence to the American Society for Gastrointestinal Endoscopy (ASGE) guidelines.The aim was to assess whether an out reach surgical service offering open access endoscopy to rural areas was being over utilized. Methods: Prospective data collection from all patients undergoing upper and lower endoscopy procedures between January 1996 and June 2000 were included in the present study. Indications for referral between the general practitioners and the visiting surgeons were reviewed in patient records and assessed for compliance with the ASGE guidelines. The groups were analysed for appropriateness of referrals and frequency of positive pathology investigations. Records for all patients undergoing colonoscopy were reviewed to determine the reason and number of cancelled procedures. Results: A total of 772 endoscopies were performed and 75% were booked as open access services. The referral rate for procedures was greater for general practitioners (583) compared to the visiting surgeons (189), the overall compliance rate for approved indications using the ASGE guidelines for both groups was 92%. There was no significant difference in pathology found between groups. Conclusion: The present study shows that an outreach rural surgical service programme in Western Australia offering open access endoscopy conforms to international guidelines and does not induce unnecessary procedures. Rural patients benefit from a personal cost savings andconvenience. There is an associated reduction in government‐assisted travel costs to larger centres as well as decreased waiting lists.     

Appropriateness of colorectal cancer screening: appraisal of evidence by experts.

OBJECTIVE: . To evaluate how the level of evidence perceived by an international panel of experts was concordant with the level of evidence found in the literature, to compare experts perceived level of evidence to their appropriateness scores, and to compare appropriateness criteria for colonoscopy between experts and an evidence-based approach. DESIGN: Comparison of expert panel opinions and systematic literature review regarding the level of evidence and appropriateness of colonoscopy indications. PARTICIPANTS: European Panel on the Appropriateness of Gastrointestinal Endoscopy multidisciplinary experts from 14 European countries. MAIN OUTCOME MEASURES: Concordance and weighted kappa coefficient between level of evidence as perceived by the experts' and that found in the literature, and between panel- and literature-based appropriateness categories. RESULTS: Experts overestimated the level of published evidence of 57 indications. Concordance between the level of evidence perceived by the experts and the actual level of evidence found in the literature was 36% (weighted kappa 0.18). Indications for colonoscopy were reported to be appropriate, uncertain, and inappropriate by the experts in 54, 19, and 27% of the cases, and by the literature in 37, 46, and 17% of the cases. A 46% agreement (weighted kappa 0.29) was found between literature-based and experts' appropriateness criteria. CONCLUSIONS: Experts often overestimated the level of evidence on which they based their decisions. However, rarely did the experts' judgement completely disagree with the literature, although concordance between panel- and literature-based appropriateness was only fair. A more explicit discussion of existing evidence should be undertaken with the experts before they evaluate appropriateness criteria.     

HYPERPLASTIC POLYPS

A colonoscopy and colonoscopic polypectomy service was established at Wellington Hospital, New Zealand in April 1975. Between April 1975 and March 1990 1157 polyps were either removed or biopsied and examined histologically. Twenty-five polyps were lost. Patient-age seemed to increase through the spectrum hyperplastic, tubular, tubulovillous, villous and polypoid carcinoma. Sessile < 6 mm in diameter hyperplastic polyps were more numerous than small adenomatous polyps. Pedunculated tumours were most commonly adenomata in all sizes, whereas sessile tumours in the rectum and sigmoid colon were usually hyperplastic. As polyp size increased the numbers of hyperplastic polyps decreased relative to the numbers of adenomatous polyps. The majority of hyperplastic polyps were found in the distal colorectum. Site distribution for hyperplastic polyps corresponded to the site distribution for colorectal carcinomata. One of five patients with hyperplastic index polyps was found to have an adenomatous polyp at follow-up. Strong evidence for a sequential relationship between hyperplastic and adenomatous polyps was not found in this study. It is unlikely that an aggressive attitude to the investigation and removal of hyperplastic polyps will have a significant effect on the later development of colorectal cancer.     

Long Term Follow-up of HNPCC Gene Mutation Carriers: Compliance with Screening and Satisfaction with Counseling and Screening Procedures

Hereditary non polyposis colorectal cancer (HNPCC) is a hereditary predisposition to colorectal and endometrial cancer, caused by mutations of the mismatch repair (MMR) genes MSH2, MLH1 and MSH6. Regular colonoscopy reduces the incidence of colorectal cancer in mutation carriers dramatically. The aim of this study was to evaluate the use of colonoscopy by proven HNPCC mutation carriers. We also evaluated the satisfaction with the counseling and screening procedures at the long term. A questionnaire survey was performed among 94 proven MMR gene mutation carriers. Data were analyzed using univariate and multivariate analysis. The average time of follow-up was 3,5 years (range 0.5–8.5 years). The response rate was 74%. The proportion of unaffected mutation carriers under colonoscopic screening increased from 31 to 88% upon genetic testing, and for gynecological screening from 17 to 69%. However, more than half of the responders experienced colonoscopy as unpleasant or painful. About 97% felt well informed during counseling, and 88% felt sufficiently supported. Ten percent of the responders reported a high cancer worry that was significantly (P = 0.007) associated with a high perceived cancer risk. Six responders (9%) regretted being tested. Remarkably, of 4 of these 6 a close relative died recently of cancer. Problems with obtaining a disability or life insurance or mortgage were experienced by 4 out 10 healthy carriers opting for these services. In conclusion, genetic testing for HNPCC considerably improves compliance for screening, which will result in a reduction of HNPCC-related cancer morbidity and mortality in mutation carriers. Most HNPCC gene mutation carriers cope well with their cancer susceptibility on the long term.     

Automated volumetry at CT colonography: a phantom study

RATIONALE AND OBJECTIVES: To assess the performance of a computer-aided detection (CAD) algorithm for measuring polyp-like structures on CT colonography (CTC) images of a phantom. MATERIALS AND METHODS: We constructed a Plexiglas phantom to which we affixed a series of idealized Plexiglas polyp-like objects, including spheres and hemispheres. We imaged the phantom in a four-channel detector CT scanner at a 1.3 mm slice thickness with a reconstruction interval of 0.6 mm, using combinations of 100 mAs, 30 mAs, horizontal and vertical orientation. For each set of CT images, the interior surface of the phantom was segmented. The CAD algorithm was applied to the resulting surface to identify the polypoid regions of interest and to calculate their volume and maximum linear dimension. Calculated values were then compared with actual values to yield percent error in each measurement. RESULTS: The mean error in volume for the subgroups of spheres and hemispheres was 3% and 5% respectively. Mean error in linear dimension was approximately 2% for both shape subgroups. All CAD-calculated values were closely correlated with their respective actual values. Parameter selection did not significantly affect the accuracy of the calculated measurements. CONCLUSIONS: Our CAD software accurately measured the greatest linear dimension and the volume of each of the polyp-like structures in our phantom. Results were largely independent of phantom orientation and the CT exposure factors.     

Support vector machines committee classification method for computer-aided polyp detection in CT colonography

RATIONALE AND OBJECTIVES: A new classification scheme for the computer-aided detection of colonic polyps in computed tomographic colonography is proposed. MATERIALS AND METHODS: The scheme involves an ensemble of support vector machines (SVMs) for classification, a smoothed leave-one-out (SLOO) cross-validation method for obtaining error estimates, and use of a bootstrap aggregation method for training and model selection. Our use of an ensemble of SVM classifiers with bagging (bootstrap aggregation), built on different feature subsets, is intended to improve classification performance compared with single SVMs and reduce the number of false-positive detections. The bootstrap-based model-selection technique is used for tuning SVM parameters. In our first experiment, two independent data sets were used: the first, for feature and model selection, and the second, for testing to evaluate the generalizability of our model. In the second experiment, the test set that contained higher resolution data was used for training and testing (using the SLOO method) to compare SVM committee and single SVM performance. RESULTS: The overall sensitivity on independent test set was 75%, with 1.5 false-positive detections/study, compared with 76%-78% sensitivity and 4.5 false-positive detections/study estimated using the SLOO method on the training set. The sensitivity of the SVM ensemble retrained on the former test set estimated using the SLOO method was 81%, which is 7%-10% greater than the sensitivity of a single SVM. The number of false-positive detections per study was 2.6, a 1.5 times reduction compared with a single SVM. CONCLUSION: Training an SVM ensemble on one data set and testing it on the independent data has shown that the SVM committee classification method has good generalizability and achieves high sensitivity and a low false-positive rate. The model selection and improved error estimation method are effective for computer-aided polyp detection.     

Preoperative Colonoscopy Decreases the Need for Laparoscopic Management of Colonic Polyps

PURPOSE Patients are commonly referred to surgeons for surgical resection of polyps that cannot be excised colonoscopically. Repeating the colonoscopy may be met with resistance by both the patient and the referring endoscopist. However, there are two distinct benefits. First, if the lesion was not marked, tattooing facilitates laparoscopic resection. Second, and more importantly, many of these polyps can be removed endoscopically by an experienced colorectal surgeon, avoiding unnecessary colon resection. Over a period of five years, we have reviewed preoperative colonoscopy in patients who were referred for surgical treatment of benign polyps.METHODS From January 1999 through September 2003 all patients referred for surgical resection of a benign polyp were consecutively entered into a database by a single group of colorectal surgeons. All patients underwent preoperative colonoscopy on the day before the planned colon resection. Patient charts were reviewed, and demographics were recorded. The referral and preoperative colonoscopy reports and all pathology results were reviewed to record the polyp size, location, histology, and subsequent treatment.RESULTS Altogether, 71 patients were included in this study. The average size of the polyps was 24 mm (range, 10–60 mm). The location of the polyp as determined by preoperative colonoscopy differed from the location noted on referral colonoscopy in nine patients (13 percent). Surgery was canceled in 23 patients (32 percent), primarily because of complete polypectomy at preoperative colonoscopy. Of the 48 who underwent surgery, 23 (47 percent) had a colonic tattoo placed, at the discretion of the surgeon. Lesions clearly located in the cecum were not tattooed routinely. Of the 48 patients who underwent surgery, 45 (94 percent) underwent laparoscopic colon resection.CONCLUSIONS We concluded that patients referred for surgical resection of a polyp should undergo repeat colonoscopy preoperatively, given that in our study one-third of patients were spared unnecessary colectomy. In addition, repeat endoscopy by the operating surgeon offers an opportunity to confirm the location of the lesion and place a colonic tattoo to facilitate laparoscopic resection.Presented at the meeting of The American Society of Colon and Rectal Surgeons, Dallas, Texas, May 8 to 13, 2004.     

Prospective Evaluation of Factors Predicting Difficulty and Pain During Sedation-Free Colonoscopy

PURPOSE Colonoscopy can be painful for patients and difficult for colonoscopists; however, it is hard to predict how painful or difficult the examination will be. This study was designed to identify factors that predict pain and difficulty during sedation-free colonoscopy.METHODS A total of 848 consecutive sedation-free colonoscopies were evaluated in a prospective manner. Factors were recorded, including patient pain, intubation time, demographic data, history of abdominal surgery, bowel preparation status, diverticular disease, bowel habits, anxiety level, and number of previous colonoscopies. These factors were analyzed to determine their association with pain and difficulty.RESULTS Almost all colonoscopies (845/848; 99.6 percent) were successful. Univariate analyses showed that lower body mass index, younger age, female gender, anxiety level, first time, intubation time, preparation status, previous hysterectomy, and previous gynecologic surgery were predictors of patient pain, and lower body mass index, female gender, anxiety level, preparation status, previous hysterectomy, previous gynecologic surgery, and constipation were predictors of difficulty of intubation. Multivariate logistic regression analyses revealed that lower body mass index, younger age, intubation time, preparation status, previous hysterectomy, and antispasmodic agent use were predictors of patient pain, and lower body mass index, female gender, constipation, preparation status, and previous hysterectomy were predictors of difficulty of intubation.CONCLUSIONS By use of intubation time and patient pain, several patient characteristics were identified that may predict technical difficulty and pain associated with the procedure. These findings have implications for the practice and teaching of colonoscopy.     

Predictors of nonadherence to screening colonoscopy

BACKGROUND: Colonoscopy has become a preferred colorectal cancer (CRC) screening modality. Little is known about why patients who are referred for colonoscopy do not complete the recommended procedures. Prior adherence studies have evaluated colonoscopy only in combination with flexible sigmoidoscopy, failed to differentiate between screening and diagnostic procedures, and have examined cancellations/no-shows, but not nonscheduling, as mechanisms of nonadherence. METHODS: Sociodemographic predictors of screening completion were assessed in a retrospective cohort of 647 patients referred for colonoscopy at a major university hospital. Then, using a qualitative study design, a convenience sample of patients who never completed screening after referral (n=52) was interviewed by telephone, and comparisons in reported reasons for nonadherence were made by gender. RESULTS: Half of all patients referred for colonoscopy failed to complete the procedure, overwhelmingly because of nonscheduling. In multivariable analysis, female sex, younger age, and insurance type predicted poorer adherence. Patient-reported barriers to screening completion included cognitive-emotional factors (e.g., lack of perceived risk for CRC, fear of pain, and concerns about modesty and the bowel preparation), logistic obstacles (e.g., cost, other health problems, and competing demands), and health system barriers (e.g., scheduling challenges, long waiting times). Women reported more concerns about modesty and other aspects of the procedure than men. Only 40% of patients were aware of alternative screening options. CONCLUSIONS: Adherence to screening colonoscopy referrals is sub-optimal and may be improved by better communication with patients, counseling to help resolve logistic barriers, and improvements in colonoscopy referral and scheduling mechanisms.