Endoscopic colorectal cancer screening: screening modality vs. screening interval

Kessler, William R.; Nehme, Omar S.
December 2003
American Journal of Gastroenterology;Dec2003, Vol. 98 Issue 12, p2796
Academic Journal
In this study by Shoen et al., the benefit of repeat sigmoidoscopy performed 3 yr after a negative examination was assessed. The patient population was composed of participants from the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial (PLCO). The mean age was 65.7 yr and 61.6% were men. Patients underwent flexible sigmoidoscopy at enrollment and 3 yr later. Procedures were performed by trained nurses, primary care physicians, and gastroenterologists. Using three variables (depth of insertion, quality of preparation, and visual findings), endoscopists placed the examination findings into one of four categories: 1) abnormal suspicious signified presence of any polyps or masses, regardless of size; 2) inadequate signified either insertion depth of <50 cm or inability to visualize 90% of the colonic mucosa; 3) abnormal, not suspicious signified endoscopic abnormalities excluding polyps and masses (i.e., hemorrhoids and diverticulosis); 4) negative signified an adequate examination without abnormality. Patients with initial examinations placed in categories 2, 3, or 4 were included in the study. Examinations were diagnostic only if lesions were neither biopsied nor removed. Lesions were classified as "distal" if they were noted in the rectum, sigmoid colon, or descending colon. Polypectomy was performed on a follow-up therapeutic procedure. Histology was read by community pathologists. Advanced adenomas were defined as adenomas ≥ 1 cm, adenomas with any villous features, or with severe dysplasia. Factors reviewed included sex, age, body mass index, education, smoking history, family history of colorectal cancer, previous endoscopy, and result of baseline screening. Of 11,583 qualifying patients, a total of 9,317 (80.4%) returned for repeat examination. In comparing repeat versus initial examination, no statistically significant difference was noted for percentage of inadequate examinations (12.3% vs 11.2%) or depth of insertion (86.7% vs 89.8%), respectively. A total of 1,292 (13.9%) patients had suspicious findings on repeat examination. Lesions were described as >1 cm in 5.5%, between 0.5 and 0.9 cm in 21.6%, and <0.5 cm in 73%. Histological data was available for only 951 patients (74.6%), as the remainder had no diagnostic follow-up. Of the 951 patients who had diagnostic follow-up, 104(10.9%) were evaluated by repeat flexible sigmoidoscopy, whereas 847 (89.1%) underwent colonoscopy. Follow-up diagnostic studies revealed that similar percentages of patients had either no suspicious abnormality, had only hyperplastic polyps, or had adenomas. Six patients (0.6%) were found to have cancer. Distal neoplastic findings included 214 nonadvanced adenomas, 72 advanced adenomas, and six cancers. Proximal neoplastic findings included 124 nonadvanced adenomas, 39 advanced adenomas, and one cancer. Of note, although 52 patients had both distal and proximal nonadvanced adenomas, 12 patients had a nonadvanced distal adenoma and an advanced proximal adenoma. The authors conclude that although the yield of repeat sigmoidoscopy for cancer and advanced adenoma 3 yr after a negative examination is much lower (2.5% vs 0.8%), when coupled with the prevalence of colorectal cancer, a longer examination interval will lead to more missed lesions and to a subsequent increase in morbidity and mortality.


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