Introduction: The effectiveness of colorectal cancer screening in reducing incident colorectal cancer and the risk of death has been shown. Despite campaigns to promote the benefits of and use of colorectal cancer screening, most people are not participating in screening. In this paper, we examine factors associated with screening behavior over time, by health care provider, and by gender and report associations between screening and development of colorectal cancer after adjusting for diet and lifestyle factors.
Methods: Data from two population-based case-control studies of colorectal cancer were used to examine risk associations with nonparticipation in colorectal cancer screening. Study participants were identified for the first study between 1991 and 1994 (N = 1,346 cases and 1,544 controls) and for the second between 1997 and 2001 (N = 952 cases and 1,205 controls) and were asked to complete a detailed in-person interviewer-administered diet and lifestyle questionnaire. The control population is used to examine changes in screening behavior and associations with screening over time.
Results: Significantly, fewer people reported fecal occult blood test (FOBT) in 1997-2001 than in 1991-1994 (62.5% in 1991-1994 vs. 47.2% in 1997-2001); a slight nonsignificant increase in sigmoidoscopy screening was reported for these periods among controls (33.9% vs. 36.6%). In the control population, during these periods, there was a statistically significant increase in the number of people who reported having had a sigmoidoscopy for screening rather than for problems (72.6% in 1997-2001 vs. 63.8% in 1991-1994). There were differences in factors associated with screening behavior by time, by sex, and by health care provider, although having a family history of colorectal cancer, having more education, and being male was associated with more screening in all settings. After adjusting for diet and lifestyle factors, we observed that non-sigmoidoscopy screening significantly influenced risk of incident cancer (rectal OR: 2.9; 95% CI, 2.3-3.7; distal tumor OR: 1.8; 95% CI, 1.4-2.3); proximal tumor: 1.4; 95% CI, 1.1-1.8). Nonuse of FOBT also was associated significantly with tumors in the rectal (OR: 1.6; 95% CI, 1.3-1.9) and distal (OR: 1.4; 95% CI, 1.1-1.8) sites.
Summary: These data reinforce the importance of screening to reduce risk of colorectal cancer development. However, flexible sigmoidoscopy screening is increasing only modestly over time, and primarily in settings where a significant investment in screening has been made. FOBT screening, which is effective for rectal cancer prevention, is actually decreasing.