Colonoscopic surveillance in asymptomatic persons with family history of colorectal cancer

The screening policy for first-degree relatives of patients with sporadic colorectal cancer has not been well-defined, especially when those patients are asymptomatic. In order to assess the potential for colonoscopic screening in this high-risk population, 409 asymptomatic person (age range: 18-74 years; mean: 39.9 ± 10.1) with only 1 affected first-degree relative received a colonoscopic examination at Chang Gung Memorial Hospital from Nov. 1993 to July 1996. In all, 41 persons, including 3 with adenocarcinoma, 1 with a adenomatous polyposis, 7 multiple adenomas, and 30 single adenomas, were identified. In the same periods, 129 asymptomatic persons (age range: 23-81 years; mean: 43.9 ± 11.1 years) who had a positive stool occult blood test and no family history of colorectal cancer received colonoscopic examinations, and 5 patients with 6 adenomas were identified. The positive detection rate in persons with a family histoy (10.0%) is higher than that in persons without a family history (3.9%) (odds ratio = 2.76, 95% C.I. = 1.07 to 7.15) despite positive stool occult blood and and a higher mean age in the latter group, which may have increased risk. Among the individuals with a family history of colorectaI cancer, 26 of the 178 older persons (> 40 years old) and 15 of the 231 younger persons (≤ 40 years old) had colorectaI neoplasm. The positive rate in older persons (14.6%) was higher than that in younger persons (6.5%) (odds ratio = 2.46, 95% C.I. = 1.26 to 4.80). These results confirm the usefulness of family history, with only one member with large bowel neoplasia in isolating a group at risk for these lesions. This group would most likely benefit from regular cancer and adenomatous polyp screening, particularly when more than 40 years old.