Updated results of the Gothenburg Trial of Mammographic Screening.

Background: There remain uncertainties about age-specific effects of breast cancer screening on mortality due to the disease.

Methods: In 1982, a randomized trial of mammographic screening every 18 months was started in Gothenburg, Sweden. Women between the ages of 39 and 49 years were randomized to an invitation to screening (intervention group; n = 11,792) or to usual care (the control group; n = 14,321). The corresponding numbers for women between the ages of 50 and 59 years were 10,112 and 15,997. Follow-up data for breast cancer mortality were available up to the end of 2007. Data were analyzed by Poisson regression with conservative variance estimates.

Results: There were 79 breast cancer deaths in the intervention arm and 156 in the control arm, and this meant a significant 30% reduction in breast cancer mortality with the offer of screening (relative risk [RR], 0.70; 95% confidence interval [CI], 0.53-0.93; P = .01). In women aged 39 to 49 years, there was a significant 40% reduction in breast cancer mortality (RR, 0.60; 95% CI, 0.43-0.85; P = .003). In the 50- to 59-year age group, there was a nonsignificant 18% breast cancer mortality reduction (RR, 0.82; 95% CI, 0.54-1.26; P = .4).

Conclusions: The policy of offering mammographic screening substantially reduces breast cancer mortality and can do so in women younger than 50 years. Cancer 2016;122:1832-5. © 2016 The Authors. Cancer published by Wiley Periodicals, Inc. on behalf of American Cancer Society.