Evaluation of the effectiveness and cost-effectiveness of colorectal cancer screening in Australia

Abstract

The National Bowel Cancer Screening Program (NBCSP) in Australia will be fully rolled out by 2020, offering free biennial screening with immunochemical Faecal Occult Blood Testing (iFOBT) to people aged 50-74 years, but current participation rates are low at 40%.

Section 1 of this thesis describes the development, calibration and validation of a microsimulation model, Policy1-Bowel, which simulates colorectal cancer (CRC) natural history and screening in Australia. I demonstrate the model’s cross-validity and external validity by comparing the estimates with other microsimulation model outcomes and with long-term CRC incidence and mortality outcomes in large randomised-controlled trials that offered guaiac FOBT or sigmoidoscopy screening.

Section 2 evaluates the effectiveness and cost-effectiveness of the current NBCSP in Australia. 2-yearly iFOBT screening at 50-74 years (i.e. the fully rolled-out NBCSP) is estimated to reduce CRC incidence and mortality by 23-33% and 36-52%, respectively, at 40-60% participation. The program is highly cost-effective due to the cancer treatment costs averted. More than 59,000 and 83,800 deaths were predicted to be prevented by the NBCSP in 2015-2040 at participation rates of 40% and 60%. It is predicted that annual expenditure on colorectal cancer control will be reduced within a decade of full rollout of the program.

Section 3 examines alternate CRC screening approaches, comparing 2-yearly iFOBT screening with screening approaches that use iFOBT, colonoscopy, sigmoidoscopy, computed tomographic colonography, faecal DNA and plasma DNA at different screening intervals in people aged 50-75 years. 2-yearly iFOBT was found to be the most cost-effective, and one of the most effective approaches. I also examine the impact of extending the NBCSP target age to include people in their forties and/or eighties. The current target age range has the most favourable benefit-to-harm balance and is the most cost-effective; extending screening to 45 years could be cost-effective, but would substantially increase colonoscopy demand and be associated with a less favourable benefits-to-harms trade-off.

The findings of the thesis suggest that fully implemented NBCSP is currently the optimal approach for CRC screening in Australia. Increasing participation in the program is a critical with potential to save tens of thousands of lives over the next two decades.