Colorectal cancer (CRC) is one of the three most common cancers in Europe, North America, Northern Africa, Western Asia, South Eastern Asia and Australia ( WHO 2003a) In the United States, in 2003 it was predicted to account for 10% of all cancer‐related deaths (ACS 2003, quoted in Chorost 2004). In the European Union, in 1995 CRC accounted for 13% of new cancer cases (ACCP 2000). In Australia, in 1990 CRC was responsible for 14% of cancer deaths (NHMRC 1999) and is the most frequently occurring cancer for new cases (AIHW 2003). Most CRCs are believed to evolve from adenomatous polyps (pre‐cancerous, visible protrusions that can develop on the mucosal surface of the colon or rectum), although most polyps do not evolve into cancer. Bowel cancer is rare in people under the age of 50, and the risk increases with age. In Australia, there is currently a 1 in 17 lifetime risk for males of being diagnosed with colorectal cancer by the age of 75 years and a 1 in 26 risk for females (AIHW 2003).

At the primary prevention level, it is believed that eating a healthy diet and exercising regularly could prevent 66‐75% of bowel cancer cases (Anonymous 2002). Unfortunately, strategies to address such risk factors as physical inactivity, overweight and consumption of foods that are high in saturated fat and/or low in fibre, require a great deal of concerted, coordinated effort, extending to the global level (WHO 2003a). Even so, It is not certain that individual risk reduction through such lifestyle modifications would ensue, and they may not be sufficiently effective as an approach to disease control (Levin 2002). In addition, some predisposing factors for colorectal cancer cannot be changed. They include older age, family history of CRC, individual history of CRC or polyps, certain hereditary conditions and inflammatory bowel disease (Gazelle 2000). However, the majority of CRCs are diagnosed in asymptomatic people whose only risk factor is age, who therefore could be considered as being at average risk (Barry 2002).

CRC is highly curable if it is diagnosed early, because it has a long pre‐clinical phase that allows detection by screening before it becomes surgically incurable (Chorost 2004). Data from South Australia show that the 5‐year survival rate is 88% for Stage A (localised disease) compared to only 7% for Stage D (distant metastases), which equates with international experience (NHMRC 1999). Screening is recommended for those of 50 years and older because the incidence of CRC begins to rise between 40 and 50 years of age. Screening guidelines vary with the method used‐for fecal occult blood testing, screening is recommended at least biennially, and preferably annually (ACCP 2000; Winawer 2003).

Fecal Occult Blood Testing (FOBT) is the most commonly used screening modality in the United States (Ransohoff 2002) and has been the focus of national bowel screening program pilots in Australia and the UK (AIHW 2003; UK CRC Pilot 2003). FOBT screening can be regarded as "a sequence of risk refinement leading to a final decision as to whether or not one should undertake the definitive diagnostic test" (NHMRC 1999). FOBT detects blood in the stool and is useful because cancers and adenomatous polyps bleed more than normal (it has been estimated that around two thirds of colon cancers bleed in the course of a week) (Chorost 2004). To date, two types of FOBT are available ‐ guaiac tests (rehydrated and non‐rehydrated) and immunochemical tests. Guaiac tests are based upon the psuedoperoxidase activity of haem. Immunochemical tests utilise antibodies against human haemoglobin. A positive result indicates the need for a diagnostic examination such as a sigmoidoscopy or colonoscopy.

However, universal consensus does not exist for the choice of FOBT as a screening programme tool (Autier 2002). Concerns exist about the sensitivity (the effectiveness of a test in detecting a cancer in those who have the disease) and specificity (the extent to which a test gives negative results in those that are free of the disease) of FOBT screening. Reported sensitivity for the detection of cancer ranges from around 40% to 90%, but only from 10% to 25% for the detection of polyps. The specificity of FOBT ranges from around 90% to 98%, depending on the type of test, (whether rehydrated or non‐rehydrated) (Gazelle 2000). This means that up to 10% of patients who undergo FOBT screening will have a false‐positive result. This propensity need not necessarily be regarded as a negative; it has been suggested that the high incidence of false‐positive results contribute towards the effectiveness of FOBT screening (Gazelle 2000). Indeed, Australian clinical practice guidelines stress that individuals should be told that it is not a diagnostic test, but a "selection process for those who should undergo colonoscopy" (NHMRC 1999). A problem arising from this approach is that those individuals with a false positive result may undergo needless anxiety, as well as the discomfort, cost and risk of colonoscopy.

Despite these limitations, FOBT screening is the safest and least expensive of the currently available screening tests (Chorost 2004; Gazelle 2000). The results of randomised trials of FOBT screening have indicated a reduction in mortality of 23% in the population that were actually screened, as well as a favourable shift in the stage distribution of colorectal cancers in the screening groups (Towler 1998). FOBT trials suggest that, after an interval of about 10 years, there could be a reduction of up to 20% in CRC mortality from biennial screening and even more from annual screening (WHO 2003b). However, these projections depend on high uptake and adherence to regular screening.

Unfortunately, initial uptake and continuing adherence to annual FOBT screening is low (Vernon 1997). A national survey undertaken in the United States in 2001 found that only 23.5% of those over 50 years had a FOBT within one year (Seeff 2003). A population uptake of less than 20% was achieved in Japan in 1998, and in Germany FOBT compliance, after a screening programme of 25 years, was only 20% for men and 30% for women (Baker 2004). Screening uptake tends to be even lower in minority groups; a survey conducted in California in 2001 found that Hispanics, Asians, and Native Hawaiians are less likely to be screened than whites or African Americans, even after adjusting for sociodemographic factors (Ponce 2003). The same survey also found that women as a population group were screened less frequently than men. A recent review examining factors affecting the utilisation of CRC screening tests (not just FOBT) in the United States concluded that fear of finding cancer and the belief that cancer is fatal results in low adherence, while a positive attitude toward screening and physician recommendation results in high adherence (Subramanian 2004). Other factors reported to be associated with reduced utilisation of FOBT include fear of pain, embarrassment, distaste, lack of perceived need, fear of the results, fatalism (belief that nothing can be done) and feeling well (Baker 2004; Rex 2002).

Intervention strategies can employ a number of "social cognitive" models which have proven effective in describing individual motivation to perform a variety of health behaviours by identifying a range of attitudinal predictors. These include the Health Belief Model (Rosenstock 1974), Protection Motivation Theory (Rogers 1975), and the Theory of Planned Behaviour (Ajzen 1991). These models can successfully map variables that describe individual differences in the intention to perform a behaviour. However, the relationship between behavioural intention and actual behaviour is less than perfect (Sheppard 1988).

There is a clear need for a deeper understanding of what are effective strategies to promote increased uptake of FOBT screening, bearing in mind that one of the most common reasons given for not having a recent colorectal screening test is the absence of any current health problems (Ponce 2003). Differences in FOBT uptake may also exist between gender, ethnic and socio‐economic groups. As an additional complication, those who choose to have an initial FOBT may not necessarily choose to adhere to repeat screenings (Craven 2001). Therefore, approaches to promote long‐term CRC screening change may differ from those required to promote the uptake of screening.