Quality‐of‐life effects of screening mammography in Norway. Issue 8 (6th September 2019) - Zahl, Per‐Henrik
Abstract : Mammography screening may save women from dying of breast cancer, although it has not been shown to reduce all‐cause mortality. Screening also leads to overdiagnosis and many false positive mammograms aggravating women's quality‐of‐life. Quality adjusted life years (QALY) analyses of mammography screening have so far, calculated life years gained assuming that all prevented breast cancer deaths translate into a reduction in all‐cause mortality. We calculated net QALYs in two hypothesized cohorts of 100, 000 Norwegian women; one screened biennially from age 50 to 69 years and one not screened. We followed both cohorts to age 85 years. We used EQ‐5D and an alternative equity weighted QALY instrument to estimate utility losses. In the screening cohort, we assumed 20% false positive tests during screening, different levels of overdiagnosis (20–75%) and different levels of breast cancer mortality reduction (10–30%). We assumed that reductions in breast cancer mortality only to a limited extent (20, 50 or 80%), resulted in reductions in all‐cause mortality. We calculated both undiscounted and discounted (4%) QALYs. Assuming that 50% of the reduction in breast cancer mortality translated to a reduction in all‐cause mortality and using estimated levels of benefits and harms in modern screening programs (50–75% overdiagnosis and 10% reduction in breast cancer mortality), undiscounted equity weighted QALY loss varied from 437 to 875 per 100, 000 women. Using the levels of benefit and harms as reported in 30–40 years old randomized trials (30% overdiagnosis and 15% reduction in breast cancer mortality), undiscounted equity weighted QALY gain was 535 per 100, 000. Net QALY in modern mammography screening in Norway is negative. Results could also be representative for Sweden, Denmark, UK and the US. Abstract : What's new? Whether current mammography screening programs are more beneficial or harmful for women remains uncertain. Here, to better understand the benefits and harms of mammography, losses in quality of life and gains in length of life were assessed using Quality Adjusted Life Years (QALY) measures in two hypothetical cohorts of Norwegian women. Follow‐up over more than three decades showed that while 10–30% of women experienced mortality reduction, 20–75% of women experienced overdiagnosis in association with mammography. The findings suggest that net QALY in current mammography screening in Norway is negative compared to when screening was initiated in the 1980s.