Long-term benefits for lower socioeconomic groups by improving bowel screening participation in South Australia: A modelling study

Introduction: The gap in bowel cancer screening participation rates between the lowest socioeconomic position (SEP) groups and the highest in Australia is widening. This study estimates the long-term health impacts and healthcare costs at current colorectal cancer (CRC) screening participation rates by SEP in South Australia (SA). Methods: A Markov microsimulation model for each socioeconomic quintile in SA estimated health outcomes over the lifetime of a population aged 50–74 years (total n = 513,000). The model simulated the development of CRC, considering participation rates in the National Bowel Cancer Screening Program and estimated numbers of cases of CRC, CRC deaths, adenomas detected, mean costs of screening and treatment, and quality adjusted life years. Screened status, stage of diagnosis and survival were obtained for patients diagnosed with CRC in 2006–2013 using data linked to the SA Cancer Registry. Results: We predict 10915 cases of CRC (95%CI: 8017─13812) in the lowest quintile (Q1), 17% more than the highest quintile (Q5) and 3265 CRC deaths (95%CI: 2120─4410) in Q1, 24% more than Q5. Average costs per person, were 29% higher in Q1 at $11997 ($8754─$15240) compared to Q5 $9281 ($6555─$12007). When substituting Q1 screening and diagnostic testing rates with Q5’s, 17% more colonoscopies occur and adenomas and cancers detected increase by 102% in Q1. Conclusion: Inequalities were evident in CRC cases and deaths, as well as adenomas and cancers that could be detected earlier. Implementing programs to increase screening uptake and follow-up tests for lower socioeconomic groups is critical to improve the health of these priority population groups.