Breast cancer mortality in participants of the Norwegian Breast Cancer Screening Program.
Bottom Line: The MRRs were adjusted for calendar period, attained age, years since inclusion in the cohorts, and self-selection bias.The mortality reduction associated with attendance in the program was 43% (MRR, 0.57; 95% confidence interval, 0.51-0.64) after adjusting for calendar period, attained age, years after inclusion in the cohort, and self-selection bias.After 15 years of follow-up, a 43% reduction in mortality was observed among women who attended the national mammographic screening program in Norway.
Affiliation: Department of Research, Cancer Registry of Norway, Oslo, Norway; Oslo and Akershus University College of Applied Sciences, Oslo, Norway.Show MeSH
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Mentions: Crude breast cancer mortality rates were 20.7 and 39.7 per 100 000 women-years in the screened and nonscreened cohorts, respectively, which resulted in a crude MRR of 0.52 (95% CI, 0.47-0.59) (Table1). A statistically significant increase in MRR was observed according to attained age and years since inclusion in the cohorts, but not according to calendar period (results not shown). The MRR was 0.39 (95% CI, 0.35-0.44) when adjusted for calendar period, attained age, and years since inclusion in the cohorts (Table1). After adjustment for self-selection bias, we obtained an MRR of 0.57 (95% CI, 0.51-0.64). An MRR of 0.75 (95% CI, 0.67-0.84) was achieved using the more conservative upper 95% CI value for D of 1.67 from Duffy et al,20 whereas using the lower 95% CI value for D of 1.11 resulted in an MRR of 0.44 (95% CI, 0.39-0.49). The difference in crude mortality rates between the 2 cohorts tended to increase with time since inclusion in the cohorts and reached a statistically significant difference after 2 years (Table2; Figs. 2,3).
Affiliation: Department of Research, Cancer Registry of Norway, Oslo, Norway; Oslo and Akershus University College of Applied Sciences, Oslo, Norway.