In 2006 the National Bowel Cancer Screening Program (NBCSP) was introduced and its progressive phasing in will be complete in 2020 when screening kits will be sent to people aged between 50 and 75 years, every 2 years. The screening uses faecal occult blood tests and those people who test positive are referred for colonoscopy. However, the participation rate in this program remains around 40%. There are more people being screened privately but despite advertising campaigns there has been only modest improvement in the uptake of screening.
What can we do to improve the situation?
Firstly, it would seem important to report the benefit that the bowel screening program is achieving. The earliest indication was after the first couple of years when kits were being sent only to 50, 60 and 65 year olds. This group was compared to those who had not received a kit, and the Australian Institute of Health and Welfare reported that those not screened had 38% higher odds of having more advanced disease when bowel cancer was eventually diagnosed. On follow-up over the next 3 years the non-invitees had a 15% higher risk of bowel cancer death (correcting for lead time bias). Those people invited to screen who did not participate had twice the chance of death when their bowel cancer was subsequently diagnosed later, than those who participated and were diagnosed by the screening.
More recently David Roder’s group analysed South Australian data to determine the relationship between pre-diagnostic colonoscopy and colorectal cancer deaths. They found that having a pre-diagnostic colonoscopy was associated with an unadjusted reduction of the risk of colorectal cancer death by 17%. Further, after making allowance for different time periods and demographic characteristics, they reported that the risk of dying from bowel cancer was reduced by 17% if people had had one colonoscopy, 27% for two and 45% for 3 pre-diagnostic colonoscopies. This shows that regular screening is important. As expected, the higher survival rates once diagnosed for the screened group is mainly due to the early stage at diagnosis.
It is clear that bowel screening saves lives, so how can the participation rates be improved? The other two population screening programs breast screen and cervical screening have participation rates of 55% and 56% nationally. Differences between these programs and bowel screening that may be relevant, aside from the fact that they have been established for longer, include the that clinicians are involved in administering the breast and cervical screening whereas the FOBT is self-administered. Also, bowel screening is the first population screening test for men, and they have a lower screening rate than women.
A further issue is that the initial bowel screening program did not formally involve primary care in recruitment, although they do receive the results if the participant nominates a GP. Research has shown that a recommendation to participate in bowel screening from a GP is a strong motivator. There are ongoing studies to find effective GP interventions that can be demonstrated to impact on screening rates.
Bowel screening both detects bowel cancer early when it is more likely to be cured by surgery but also detects polyps which may evolve into cancer and they can be removed to prevent cancer. This not only reduces bowel cancer in the population but is far more cost- effective than treating established bowel cancer where high-cost targeted therapies are being added to cytotoxics, particularly for metastatic disease.
If public health messaging about screening has been a challenge, the message of preventing bowel cancer by lifestyle changes is even more difficult to affect change. Diets with more fibre and less meat and processed meats, less alcohol and less calories to prevent obesity, along with an increase in vigorous exercise each week, often require significant changes from how the majority of the population live. Daily low dose aspirin will reduce the risk of developing bowel cancer in high-risk individuals but the evidence of where the balance lies between efficacy and side effects in the rest of the population has been more difficult to interpret and give strong recommendations.
In summary, everyone, working in specialties or primary care, can play a role in raising awareness of the potential for preventing bowel cancer deaths by screening and lifestyle changes. Those younger than the screening age in whom bowel cancer has been increasing over the past 15 years, also need to be aware that they can develop bowel cancer and although uncommon, they should not ignore symptoms and should present as early as possible.
Even with no further breakthrough treatment or insights we can significantly reduce bowel cancer and bowel cancer deaths by fully implementing what we already know to be effective.