Estimation of life years gained in population-based cancer screening programs

Abstract

Due to the potential negative consequences of cancer screening programmes and the substantial resources invested in them, it is important to monitor their effectiveness. Mortality in the target population is one indicator that can be used to demonstrate the long-term effectiveness of organized, population-based screening programmes—after 10 to 20 years, mortality in the target population is expected to decrease by 20–30%. One of the main limitations of the mortality indicator is that, particularly for cancers with good survival rates, it only shows the effectiveness of screening over a long period of time. Therefore, survival analysis, where results are available earlier, is often used to evaluate the effectiveness of population- based cancer screening programmes. It is recognized that a number of biases can creep into the results of survival analysis (e.g. lead, length and overdiagnosis bias). Recently, Slovenian researchers have proposed a new analytical approach that allows a comparison of survival rates for cancers detected and undetected in the screening programme, taking into account all relevant biases. The calculated survival rates form the basis for the calculation of life years gained, a measure that expresses the additional number of years of life that people live as a result of participating in the screening programme. In the test case, we assessed the impact of the introduction of the National Breast Cancer Screening Programme DORA, which was first offered to residents in 2008 and expanded to the entire population in 2018. Women invited to the DORA programme in the period 2008–2022 gained a total of 90.6 life years. If all women had been included in the DORA programme since 2008, they would have gained 552.7 years of life. The total number of life years gained increases with each additional year of observation that individual women survive after enrolment in the DORA programme. The new method will help in the management of existing cancer screening programmes, their promotion and the evaluation of the impact of changes in screening policy.

Keywords

• organized screening programme
• performance evaluation
• cancer registry
• breast cancer
• life years gained