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Analysis of Colorectal Cancer Occurrence During Surveillance Colonoscopy in the Dietary Polyp Prevention Trial
**674 Colonoscopic Miss Rates for Colorectal Cancer: A Population Based Analysis Brian Bressler, Lawrence Paszat, Chris Vinden, Jingsong He, Cindy Li, Linda Rabeneck Background: The gold standard for the diagnosis of colorectal cancer (CRC) is colonoscopy (COL). However, COL does contain an inherent miss rate for CRC. Previous reports evaluated miss rates in patients seen in academic centers or units with endoscopists known for their expertise. The CRC miss rate of COL performed in the course of usual clinical practice is unknown. Objective: To determine the proportion CRCs missed during COL. Methods: Using electronic data from the Canadian Institute for Health Information and the Ontario Health Insurance Program (OHIP), we identified all individuals older than 18 years old, with a new diagnosis of CRC, in the province of Ontario from 1/4/1997 to 31/3/ 2001. We excluded all individuals with synchronous, site unspecified, or location coded as other CRC. We excluded those with CRC in the descending colon and splenic flexure because we are unable to determine the depth of insertion of the instrument for those locations. We also excluded those who did not have a COL (or flexible sigmoidoscopy in those with rectal or sigmoid CRC) within 3 years prior to their diagnosis. The remaining individuals comprised our study cohort. We separated our cohort into three groups: right-sided (CRC in cecum or ascending colon), transverse CRC, and rectal or sigmoid CRC. We divided each group into two categories. The detected cancers category consisted of individuals who had lower gastrointestinal (GI) endoscopy within 6 months prior to the diagnosis (in this category we assumed the endoscopic procedure identified the cancer); the missed cancers category consisted of those who had lower GI endoscopy 6-36 months prior to the diagnosis (in this category we assumed the endoscopic procedure missed the cancer). Results: We identified 31,553 patients with a new diagnosis of CRC and excluded 21,366 because they were diagnosed with synchronous, site unspecified, location coded as other CRC, descending colon, or splenic flexure CRC, or did not have a COL within 3 years of their CRC diagnosis. The remaining 10,187 patients comprised our study cohort, of whom 2,580 had right-sided CRC, 702 had transverse CRC, and 6,905 had rectal or sigmoid CRC. The proportions of missed cancers were: 157 patients (6%) with right-sided CRC, 29 patients (4%) with transverse CRC, and 207 patients (3%) with rectal or sigmoid CRC. Conclusion: The proportion of CRCs missed by colonoscopy in usual clinical practice varies between 3-6% depending on the location of the CRC. When consent is obtained for colonoscopy patients need to be informed of the risk of missing CRC.
**675 Analysis of Colorectal Cancer Occurrence During Surveillance Colonoscopy in the Dietary Polyp Prevention Trial Ajay Pabby, Robert E. Schoen, Joel L. Weissfeld, Randall Burt, James W. Kikendall, M. Peter Lance, Moshe Shike, Elaine Lanza, Arthur Schatzkin Colonoscopy can reduce mortality and incidence of colorectal cancer (CRC). However, interval CRC is occasionally detected in subjects with recent colonoscopy. Systematic evaluation of the reasons for interval cancer may be helpful in improving the quality of colonoscopy and in developing guidelines for surveillance. Methods: The Polyp Prevention Trial (PPT) was a randomized, controlled study evaluating the effect of a dietary intervention on adenomatous polyp recurrence. Subjects underwent a baseline colonoscopy (T0 exam) for eligibility, and were scheduled to undergo a repeat exam at 1 and 4 years. We examined the circumstances surrounding the diagnosis of CRC in the PPT population including demographic information, T0 colonoscopy findings, time interval to cancer diagnosis, location, size, and staging. An algorithm was developed to analyze and classify each cancer occurrence into one of four etiologies: 1) Incomplete polyp removal (with subsequent cancer at that site), 2) False negative biopsy (where a suspicious area was biopsied but cancer was not detected), 3) Missed cancer (cancer that occurred in a different location from the site of previous polyp removal and was diagnosed in a relatively short time frame from the most recent colonoscopy), and 4) New cancer. Results: Of 2079 patients, 15 cancers developed in 14 subjects (0.67%) over 5810 person years of observation (PYO)(2.4 cases/1000 PYO). 71.4%(10/14) had an advanced adenoma and 50% had $2 adenomas detected at the baseline examination. The cancers were found throughout the colon; 53.3% (8/15) were proximal to the splenic flexure and 33.3% (5/15) were in the cecum or at one of the flexures. Based on our analysis, 7/14 or 50% of patients had a potentially ‘‘avoidable’’ cancer, with diagnosis due to incomplete removal of an advanced adenoma with cancer developing at that site subsequently (4/14) or an apparent missed cancer (3/14). The ‘‘incomplete removal’’ category highlights the importance of assuring the complete excision of advanced adenomas. Missed cancers were relatively large and were all located proximal to the hepatic flexure, emphasizing the importance of assuring cecal intubation. Conclusion: Interval cancers occur with some frequency despite colonoscopy. Improved colonoscopy quality and follow up of potential incompletely removed high risk adenomas may have reduced cancer incidence, or resulted in earlier cancer detection in up to 50% of incident cancers in the PPT.
P110
GASTROINTESTINAL ENDOSCOPY
**676 Impact of Virtual Reality Simulator Training on the Acquisition of Competency in Colonoscopy: Final Results of Multi-Center Randomized Controlled Trial Jonathan Cohen, Seth Cohen, Kinjal C. Vora, New York Society for Gastrointestinal Endoscopy (NYSGE) Study Group, J. Steven Burdick, Robert H. Hawes, Xiaonan Xue BACKGROUND: The GI MentorÔ is a virtual reality endoscopy simulator which uses force feedback technology to create a realistic training experience. We conducted a randomized blinded comparison of simulator training vs no simulator training to define the benefit of simulator training. METHODS: First year GI fellows were randomized to receive 10 hours of unsupervised training on the GI MentorÔor no simulator experience during the first 8 weeks of fellowship. Fellows performed all procedures except colonoscopy during this time. After this period, both groups began performing real colonoscopy. The first 200 colonoscopies performed by each fellow were graded by proctors to measure technical and cognitive success, subjective competency and patient comfort level. Objective competency for a procedure was defined as unassisted examination to the cecum with correct recognition and identification of abnormalities. RESULTS: 45 fellows were randomized from 16 hospitals over 2 years. Pre-colonoscopy experience in other procedures and the # of failed examinations rated as difficult for the proctor were similar in the 2 groups. Fellows in the simulator group had significantly higher objective competency rates during the first 100 cases. A mixed effects model demonstrated higher objective competence overall in the simulator group (p < 0.0001) with the difference between groups being significantly greater during the first 80 cases performed than during the latter cases. The median # of cases needed to reach 90% competency was 160 in both groups. Patient comfort level was similar in the two groups. CONCLUSION: Fellows who undergo colonoscopy training for 10 hours on the GI MentorÔ perform significantly better during the early phase of real colonoscopy training. Almost all trainees reach full competency by 200 colonoscopies. Study funded by ASGE Outcomes & Effectiveness Award.
**677 Clinical Importance of Flat and Depressed Lesions in American Veterans with in situ and Submucosally Invasive Colorectal Adenocarcinoma Karen C. Kim, Shai Friedland, Robert V. Rouse, Jon Kosek, Suzanne M. Matsui, Roy M. Soetikno Background: Flat and depressed colorectal neoplasms (FDCN) can be found among Western patients. However, the clinical significance of these lesions in the United States is unclear. This study was designed to clarify the incidence of endoscopically flat and depressed neoplasms among in situ and submucosally invasive colorectal adenocarcinoma diagnosed in American patients. Methods: Through visits to a number of Japanese endoscopy units and self-training, we have developed a team of American endoscopists who are familiar with the techniques used to diagnose and treat FDCN since 2000. We routinely use the Japanese macroscopic classification of early colorectal cancer. We used our prospectively entered pathology database to identify cases of in situ and submucosally invasive adenocarcinoma (T1) that were diagnosed between January 2000 to September 2003. We correlated pathologic diagnosis with endoscopic findings, and used t-test and Chi-square for statistical comparisons. Results: Of 118 neoplasms, 75 (63.6%) were CIS and 43 (36.4%) were invasive to the submucosa (T1). Of the CIS lesions, 11 (15%) were flat or depressed, and 64 (85%) were polypoid. Of the early invasive cancers, 13 (30%) were flat or depressed, and 30 (70%) were polypoid. Flat and depressed lesions were smaller than polypoid lesions, with mean size of 1.3 +/ÿ 0.7 cm vs 2.0 +/ÿ 1.0 cm, respectively (p = 0.0001). Flat and depressed lesions were found throughout the colon. In contrast, polypoid lesions were more likely to be found in the left colon (p=0.03). The mean age of patients of both groups was similar (p=ns). All but two of the patients were male. Conclusions: Flat and depressed-appearing colorectal lesions are common among in situ and submucosally invasive adenocarcinoma found in American veterans. They account for approximately 15% and 30% of in situ and submucosally invasive adenocarcinoma, respectively. They are found in patients of similar age when compared to those with polypoid lesions of similar pathology, are located throughout the colon, and are smaller in size than polypoid lesions.
VOLUME 59, NO. 5, 2004
**675 Analysis of Colorectal Cancer Occurrence During Surveillance Colonoscopy in the Dietary Polyp Prevention Trial Ajay Pabby, Robert E. Schoen, Joel L. Weissfeld, Randall Burt, James W. Kikendall, M. Peter Lance, Moshe Shike, Elaine Lanza, Arthur Schatzkin Colonoscopy can reduce mortality and incidence of colorectal cancer (CRC). However, interval CRC is occasionally detected in subjects with recent colonoscopy. Systematic evaluation of the reasons for interval cancer may be helpful in improving the quality of colonoscopy and in developing guidelines for surveillance. Methods: The Polyp Prevention Trial (PPT) was a randomized, controlled study evaluating the effect of a dietary intervention on adenomatous polyp recurrence. Subjects underwent a baseline colonoscopy (T0 exam) for eligibility, and were scheduled to undergo a repeat exam at 1 and 4 years. We examined the circumstances surrounding the diagnosis of CRC in the PPT population including demographic information, T0 colonoscopy findings, time interval to cancer diagnosis, location, size, and staging. An algorithm was developed to analyze and classify each cancer occurrence into one of four etiologies: 1) Incomplete polyp removal (with subsequent cancer at that site), 2) False negative biopsy (where a suspicious area was biopsied but cancer was not detected), 3) Missed cancer (cancer that occurred in a different location from the site of previous polyp removal and was diagnosed in a relatively short time frame from the most recent colonoscopy), and 4) New cancer. Results: Of 2079 patients, 15 cancers developed in 14 subjects (0.67%) over 5810 person years of observation (PYO)(2.4 cases/1000 PYO). 71.4%(10/14) had an advanced adenoma and 50% had $2 adenomas detected at the baseline examination. The cancers were found throughout the colon; 53.3% (8/15) were proximal to the splenic flexure and 33.3% (5/15) were in the cecum or at one of the flexures. Based on our analysis, 7/14 or 50% of patients had a potentially ‘‘avoidable’’ cancer, with diagnosis due to incomplete removal of an advanced adenoma with cancer developing at that site subsequently (4/14) or an apparent missed cancer (3/14). The ‘‘incomplete removal’’ category highlights the importance of assuring the complete excision of advanced adenomas. Missed cancers were relatively large and were all located proximal to the hepatic flexure, emphasizing the importance of assuring cecal intubation. Conclusion: Interval cancers occur with some frequency despite colonoscopy. Improved colonoscopy quality and follow up of potential incompletely removed high risk adenomas may have reduced cancer incidence, or resulted in earlier cancer detection in up to 50% of incident cancers in the PPT.
P110
GASTROINTESTINAL ENDOSCOPY
**676 Impact of Virtual Reality Simulator Training on the Acquisition of Competency in Colonoscopy: Final Results of Multi-Center Randomized Controlled Trial Jonathan Cohen, Seth Cohen, Kinjal C. Vora, New York Society for Gastrointestinal Endoscopy (NYSGE) Study Group, J. Steven Burdick, Robert H. Hawes, Xiaonan Xue BACKGROUND: The GI MentorÔ is a virtual reality endoscopy simulator which uses force feedback technology to create a realistic training experience. We conducted a randomized blinded comparison of simulator training vs no simulator training to define the benefit of simulator training. METHODS: First year GI fellows were randomized to receive 10 hours of unsupervised training on the GI MentorÔor no simulator experience during the first 8 weeks of fellowship. Fellows performed all procedures except colonoscopy during this time. After this period, both groups began performing real colonoscopy. The first 200 colonoscopies performed by each fellow were graded by proctors to measure technical and cognitive success, subjective competency and patient comfort level. Objective competency for a procedure was defined as unassisted examination to the cecum with correct recognition and identification of abnormalities. RESULTS: 45 fellows were randomized from 16 hospitals over 2 years. Pre-colonoscopy experience in other procedures and the # of failed examinations rated as difficult for the proctor were similar in the 2 groups. Fellows in the simulator group had significantly higher objective competency rates during the first 100 cases. A mixed effects model demonstrated higher objective competence overall in the simulator group (p < 0.0001) with the difference between groups being significantly greater during the first 80 cases performed than during the latter cases. The median # of cases needed to reach 90% competency was 160 in both groups. Patient comfort level was similar in the two groups. CONCLUSION: Fellows who undergo colonoscopy training for 10 hours on the GI MentorÔ perform significantly better during the early phase of real colonoscopy training. Almost all trainees reach full competency by 200 colonoscopies. Study funded by ASGE Outcomes & Effectiveness Award.
**677 Clinical Importance of Flat and Depressed Lesions in American Veterans with in situ and Submucosally Invasive Colorectal Adenocarcinoma Karen C. Kim, Shai Friedland, Robert V. Rouse, Jon Kosek, Suzanne M. Matsui, Roy M. Soetikno Background: Flat and depressed colorectal neoplasms (FDCN) can be found among Western patients. However, the clinical significance of these lesions in the United States is unclear. This study was designed to clarify the incidence of endoscopically flat and depressed neoplasms among in situ and submucosally invasive colorectal adenocarcinoma diagnosed in American patients. Methods: Through visits to a number of Japanese endoscopy units and self-training, we have developed a team of American endoscopists who are familiar with the techniques used to diagnose and treat FDCN since 2000. We routinely use the Japanese macroscopic classification of early colorectal cancer. We used our prospectively entered pathology database to identify cases of in situ and submucosally invasive adenocarcinoma (T1) that were diagnosed between January 2000 to September 2003. We correlated pathologic diagnosis with endoscopic findings, and used t-test and Chi-square for statistical comparisons. Results: Of 118 neoplasms, 75 (63.6%) were CIS and 43 (36.4%) were invasive to the submucosa (T1). Of the CIS lesions, 11 (15%) were flat or depressed, and 64 (85%) were polypoid. Of the early invasive cancers, 13 (30%) were flat or depressed, and 30 (70%) were polypoid. Flat and depressed lesions were smaller than polypoid lesions, with mean size of 1.3 +/ÿ 0.7 cm vs 2.0 +/ÿ 1.0 cm, respectively (p = 0.0001). Flat and depressed lesions were found throughout the colon. In contrast, polypoid lesions were more likely to be found in the left colon (p=0.03). The mean age of patients of both groups was similar (p=ns). All but two of the patients were male. Conclusions: Flat and depressed-appearing colorectal lesions are common among in situ and submucosally invasive adenocarcinoma found in American veterans. They account for approximately 15% and 30% of in situ and submucosally invasive adenocarcinoma, respectively. They are found in patients of similar age when compared to those with polypoid lesions of similar pathology, are located throughout the colon, and are smaller in size than polypoid lesions.
VOLUME 59, NO. 5, 2004