Melbourne School of Population and Global Health - Theses
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ItemColorectal cancer screening in Australia: what is the role of family history?( 2012)Colorectal cancer (CRC) is the third most common cancer suffered throughout the world, with nearly one million new cases diagnosed world-wide each year and half a million deaths. Due to demographic trends, significantly more individuals will be confronted with CRC in the future. Therefore, its control has become a major public health issue for industrialised countries. Australia has one of the highest CRC incidence rate in the world. It is the second most frequently diagnosed cancer and the second largest cause of cancer deaths in Australia (14,234 new cases and 4,047 deaths in 2007). Approximately 15% to 30% of these cases occur in just the 2% of the population with a strong family history of the disease. The characteristics of colorectal cancer fulfill the conditions that make mass screening useful and beneficial for public health: strong incidence, poor prognosis, a typically long pre-symptomatic latency period, effective treatment in early stages of the disease, it is preceded by a precancerous lesion in 95% of cases and there are testing methods which are scientifically proven to be effective at reducing mortality. Screening for colorectal cancer has been shown to be an effective method to reduce both incidence and mortality, and for several years now, international scientific consensus has recognised the need for setting up mass screening initiatives for colorectal cancer. In 2006 the Australian government introduced a national bowel cancer screening programme (NBCSP) using faecal occult blood test but only for people tuning 50, 55 or 65 years of age. The latest data from the programme published in 2010 showed that only 40% of those invited to screen actually performed the test. The primary aim of my thesis was to investigate the CRC screening practices taking place outside of the current national programme based on the current screening guidelines recommendations. I conducted two systematic reviews of the literature to determine the predictors of screening for people at familial-risk of CRC and the level of screening uptake in that population. I identified a low level of screening participation among people at increased risk of CRC and that family history of CRC and physicians’ recommendation to screen were the most consistent predictors of CRC screening uptake. Overall, I found only a small number of studies investigating the screening practices of those most at risk of CRC, with important methodological shortcomings in their analyses. I investigated CRC screening practices in Australia based on the Colorectal Cancer Family Registry (ACCFR) study. 3845 participants were classified into four risk categories according to the strength of their family history of CRC based on current Australian guidelines. Among participants categorised “at or slightly above” average risk of CRC (represent 98% of the general population) eligible for screening, 90% reported never having been screened and 8% reported over-screening. Middle- aged people, those with a family history of CRC and those with a university degree were more likely to be over-screened. For participants categorised “at moderately increased-risk” or “potentially high-risk” of CRC (represents the 2% of the general population in which 15-30% of all CRC occur), 95% were underscreeners and only 5% reported guideline-defined “appropriate” screening. People of middle-age, higher education and who had resided in Australia longer were more likely to have had screening for CRC in this risk category. In a cost-effectiveness analysis of screening strategies addressed to people at increased risk of CRC due to family history, I found that biennial screening with immunochemical faecal occult blood test, colonoscopy every ten years or colonoscopy every five years reduced the number of CRC cases by 11%, 22% and 34% respectively. All three strategies had an incremental cost-effectiveness ratio (ICER) under $50,000 per life-year gained (LYG), which is regarded as the upper limit of acceptable cost-effectiveness for screening technologies in the Australian health system. At $16,924 per LYG, colonoscopy screening every five-year appears to be the most cost-effective strategy. Overall, my results show that current guidelines for CRC screening are not being implemented in the population. CRC screening participation is low across all risk categories and the vast majority of screening tests undertaken were inappropriate in terms of timing, modality or frequency. Finally, family-history-based CRC screening is a cost-effective strategy and should be considered as an option to increase participation among those most at risk of developing CRC.