Adherence to screening examinations for colorectal cancer after diagnosis in a first-degree relative.

Reports of colorectal cancer screening behavior were collected from 83 twin sisters of colorectal cancer cases and compared to the patterns found by national surveys. Prior to the diagnosis of colorectal cancer in a twin, the unaffected cotwins were being screened at rates close to those of the general population. In the years after diagnosis the annual frequency of each exam increased by approximately 15 to 20 percentage points. By the time of response nearly 89% of these cotwins had at least one fecal occult blood test, 90% had at least one digital rectal exam, and 69% had a sigmoidoscopy in comparison to 44, 63, and 27% of the general population, respectively. However, despite the evident familial risk, within the year prior to the report, 42.3% of colorectal cancer twins had had a fecal occult blood test, 44.3% had had a digital rectal exam, and 16% had had a sigmoidoscopy exam (the comparable figures from the general population sample are 14.5, 19.3, and 4%, respectively). The colorectal cotwins have a higher rate of sigmoidoscopy screening than either the National Health Interview Survey or the breast cotwins. Both colorectal and breast cancer cotwins have a higher rate of fecal occult blood test and digital rectal exam than the NHIS sample. This suggests that those at increased risk of cancer in general, are more likely to obtain routine screening including fecal occult blood test and digital rectal exam as part of the physical exam; however, the specialized sigmoidoscopy screening is more likely to be provided to those at most risk.