Publication Abstract

Authors: Zahl PH, Strand BH, Maehlen J

Title: Incidence of breast cancer in Norway and Sweden during introduction of nationwide screening: prospective cohort study.

Journal: BMJ 328(7445):921-4

Date: 2004 Apr 17

Abstract: OBJECTIVE: To determine whether any increase in the incidence of breast cancer in women detected by mammography is compensated for by a drop in the incidence after age 69, years when women are no longer invited for screening. DESIGN: Population based cohort study of incidence of breast cancer during the introduction of nationwide screening programmes. SETTING: Norway and Sweden. PARTICIPANTS: All women aged above 30 years (1.4 and 2.9 million, respectively, in 2000). MAIN OUTCOME MEASURES: Changes in age specific incidence rates of invasive breast cancer associated with the introduction of the screening programmes. RESULTS: As a result of screening the recorded incidence of breast cancer in women aged 50-69 years increased by 54% in Norway and 45% in Sweden. There was no corresponding decline in incidence after the age of 69 years. CONCLUSIONS: Without screening one third of all invasive breast cancers in the age group 50-69 years would not have been detected in the patients' lifetime. This level of overdiagnosis is larger than previously reported.