Sex and race are risk factors for colorectal cancer within reach of the sigmoidoscope.

There is controversy about the efficacy and feasibility of flexible fiberoptic sigmoidoscopy (FFS) as a screening test for colorectal cancer in asymptomatic adults aged 50 years and over. Some authorities recommend periodic FFS screening for all such adults, whereas other authorities do not recommend screening FFS at all. There is evidence that some physicians have adopted a policy of "selective screening" by emphasizing screening FFS for adults with ancillary risk factors such as a personal history of colon polyps or previous colorectal cancer, or a family history of colon, female genital, or breast cancer. Results of this study of the subsite distribution of colorectal cancer show that both male sex and Oriental race are risk factors for colorectal cancer within reach of FFS, and that the risk of being male and Oriental (relative risk [RR] = 1.9) is of the same magnitude as that for other ancillary risk factors known for the general population (excluding specific rare disorders). Knowledge that sex and race are risk factors for colorectal cancer detectable by screening FFS may be important to those physicians who choose the selective screening approach. Further research is necessary to determine whether selective screening for colorectal cancer is efficacious, or whether the race and sex differences noted in this study are important in the etiology of colorectal cancer.