Quality-adjusted life years in the presence and absence of organized mammographic screening using data from BreastScreen Norway.

Benefits and harms of breast cancer (BC) screening with mammography have been debated and, although most studies reported positive effects, some studies found a negative effect in terms of net quality-adjusted life years (QALYs). We aimed to estimate net QALYs associated with biennial mammographic screening for women aged 50-69 years offered to 100,000 women followed until age 85, using various assumptions on BC mortality reduction, overdiagnosis and mortality transfer (the extent to which a reduction in BC mortality results in a reduction in all-cause mortality). Individual-level data from women invited to BreastScreen Norway during 1996-2020 were used to perform the calculations. The three baseline scenarios included (1) Model Microsimulation Screening Analysis (MISCAN): MISCAN prediction for mortality reduction and overdiagnosis proportion; (2) Model A: 40% BC mortality reduction and 15% overdiagnosis; and (3) Model B: 20% BC mortality reduction and 50% overdiagnosis. For all scenarios, an 80% mortality transfer was assumed. An online tool was developed to illustrate the impact of alternative assumptions. Biennial organized mammographic screening for women aged 50-69 years who were followed until the age of 85 years was associated with 6819, 7444 and 2446 net QALYs gained per 100,000 women for Model MISCAN, A and B, respectively. Assumptions on BC mortality reduction exhibited the largest impact on net QALYs. To conclude, even when assuming a high overdiagnosis proportion and low BC mortality reduction, net QALYs remained positive, reinforcing the value of offering BC screening with mammography to Norwegian women and showing its potential to improve health outcomes.