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


METHODS
Population based cohort study of incidence of breast cancer during the introduction of nationwide screening programmes.


METHODS
Norway and Sweden.


METHODS
All women aged above 30 years (1.4 and 2.9 million, respectively, in 2000).


METHODS
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.
Zahl
Per-Henrik
PH
Norwegian Institute of Public Health, PO Box 4404 Nydalen, N-0403 Oslo, Norway.
Strand
Bjørn Heine
BH
Maehlen
Jan
J
D000328:Adult; D017677:Age Distribution; D000368:Aged; D001943:Breast Neoplasms / Q000453:epidemiology*; D015331:Cohort Studies; D005260:Female; D006801:Humans; D015994:Incidence; D008403:Mass Screening; D008875:Middle Aged; D009664:Norway / Q000453:epidemiology; D011446:Prospective Studies; D013548:Sweden / Q000453:epidemiology