Colorectal cancer is the third most commonly diagnosed cancer and the fourth leading cause of death in the world. There are few published studies that have used theory-based interventions designed to increase colorectal cancer screening in community lay health organizations. The present study was guided by the theoretical concepts of the preventive health model. Twelve health clubs of a municipal district in Tehran were randomized to two study groups with equal ratio. The control group received usual services throughout the study while the intervention group also received a theory-based educational program on colorectal cancer screening plus a reminder call. Screening behavior, the main outcome, was assessed 4 months after randomization. A total of 360 members aged 50 and older from 12 health clubs completed a baseline survey. Participants in the intervention group reported increased knowledge of colorectal cancer and screening tests at 4 months follow-up (p’s < .001). Moreover, exposure to the theory-based intervention significantly improved self-efficacy, perceived susceptibility, efficacy of screening, social support, and intention to be screened for colorectal cancer, from baseline to 4 months follow-up (p’s < .001). The screening rate for colorectal cancer was significantly higher in the intervention group compared to the control group (odds ratio = 15.93, 95 % CI = 5.57, 45.53). Our theory-based intervention was found to have a significant effect on colorectal cancer screening use as measured by self-report. The findings could have implications for colorectal cancer screening program development and implementation in primary health care settings and through other community organizations.
