Adherence and the Economics of Colon Cancer Screening

Colorectal cancer (CRC) is a significant and preventable disease, yet CRC screening rates remain low. Previous investigators have identified barriers to adherence to CRC screening; however, the majority of data have been retrospectively derived, and the limited data produced from prospective assessment have been limited to fecal occult blood testing (FOBT). Constructs based on the Health Belief Model have been proposed to identify items associated with non-adherence to CRC screening, but prospective validation of this model is lacking. The U.S. Preventive Services Task Force report cites a major cause of uncertainty for calculation of the incremental cost-effectiveness of CRC screening is the deficit in primary data regarding adherence to CRC screening tests, specifically whether heterogeneity exists in screening rates of competing strategies. The Institute of Medicine confirmed the importance of detecting heterogeneity in adherence between strategies, understanding that some strategies currently recommended for CRC screening may be dominated by strategies that achieve greater levels of adherence.

This study aims to determine whether adherence rates to CRC screening are heterogeneous between competing strategies (FOBT and colonoscopy). This study will also prospectively examine domains of the Health Belief Model to identify associations with non-adherence to screening. Adherence rates specific to tested strategies will be incorporated in our existing economic models to compare the incremental cost-effectiveness of competing CRC screening strategies. These data will greatly impact policy decisions regarding resource allocation for CRC screening. It is also expected that future research based on data generated through this project will aim to develop and test interventions that optimize adherence to screening strategies to decrease mortality from CRC.

Procedures:

Patients who are due for CRC screening and meet eligibility requirements are identified through a query of the electronic medical record database at San Francisco General Hospital (SFGH). A research assistant (RA) obtains the PCP's approval to attempt recruitment at the patient's primary care appointment. The PCP discusses CRC screening with the participant during their regularly scheduled appointment.

Availability of CRC screening tests: Because of capacity constraints in the endoscopy unit at SFGH, the screening method for those at average risk of CRC had been limited to annual fecal occult blood testing (FOBT). However, the gastroenterology department initiated a pilot program which allows different primary care clinics to refer average-risk patients for colonoscopy screening in rotating 3-month time-blocks. To ensure the endoscopy unit has sufficient capacity to provide CRC screening via colonoscopy, providers in a given primary care clinic are able to refer their patients for (a) colonoscopy screening, (b) FOBT screening, or (c) a choice of either colonoscopy or FOBT screening, depending on the time block. This is not a study intervention; providers simply recommend that their patients complete a standard CRC screening test, and discuss the option or options available. Patients who decline to participate in the study undergo colorectal cancer screening under the guidance of their primary care provider; the same screening tests are available to those who participate and those who do not.

After giving written informed consent, participants complete an RA-administered 20-minute survey based on constructs of the Health Belief Model. Participants also grant us approval to review their medical records in one year to determine if they complete screening; those without a record of testing are contacted to determine if they completed testing outside of SFGH.