Mammographic screening and mortality from breast cancer: the Malmö mammographic screening trial
Andersson, I.; Aspegren, K.; Janzon, L.; Landberg, T.; Lindholm, K.; Linell, F.; Ljungberg, O.; Ranstam, J.; Sigfússon, B.
Bmj 297(6654): 943-948
1988
ISSN/ISBN: 0959-8138 PMID: 3142562 DOI: 10.1136/bmj.297.6654.943Document Number: 356269
Study objective.sbd.To determine whether mortality from breast cancer could be reduced by repeated mammographic screening. Design.sbd.Birth year cohorts of city population separately randomised into study and control groups. Setting.sbd.Screening clinic outside main hospital. Patients.sbd.Women aged over 45; 21088 invited for screening and 21195 in control group. Interventions.sbd.Women in the study group were invited to attend for mammographic screening at intervals of 18-24 months. Five rounds of screening were completed. Breast cancer was treated according to stage at diagnosis. Endpoint.sbd.Mortality from breast cancer. Measurements and main results.sbd.All women were followed up and classed at end point as alive without breast cancer, alive with breast cancer, dead from breast cancer, or dead from other causes. Cause of death was taken from national mortality registry and for patients with breast cancer was validated independently. Mean follow up was 8.8 years. Altogether 588 cases of breast cancer were diagnosed in the study group and 447 in the control group; 99 v 94 women died of all causes and 63 v 66 women died of breast cancer (no significant difference; relative risk 0.96 (95% confidence interval 0.68 to 1.35)). In the study group 29% more women aged > 55 died of breast cancer (28 v 22; relative risk 1.29 (0.74 to 2.25)). More women in the study group died from breast cancer in the first seven years; after that the trend reversed, especially in women aged .gtoreq. 55 at entry. Overall, women in the study group aged .gtoreq. 55 had a 20% reduction in mortality from breast cancer (35 v 44; relative risk 0.79 (0.51 to 1.24)). Other findings.sbd.In the study group 100 (17%) cancers appeared in intervals beween screenings and 107 (18%) in non-attenders; 51 of these women died from breast cancer. Cancers classed as stages II-IV comprised 33% (190/579) of cancers in the study group and 52% (231/443) in the control group. Conclusions.sbd.Invitation to mammograpihc screening may lead to reduced mortality from breast cancer, at least in women aged 55 or over.