[Mammography screening in the county of Copenhagen. Results of the first three screening rounds].

INTRODUCTION

Biennial service mammography screening for breast cancer has been offered to women aged 50-69 years in the municipality of Copenhagen since 1991. We report the results of the first three invitation rounds.

MATERIAL AND METHODS

Data were collected from the Copenhagen service mammography screening database and other Danish registers.

RESULTS

The average participation rate during the first three invitation rounds was 66%. The breast cancer detection rate was 10/1,000 screened in the first invitation round and 5/1,000 in the consecutive rounds. The probability of a false positive mammography was 6% at the prevalent screen, and this was reduced to 3% at incidence screens. Fifty-two cases of interval cancer were seen after the first invitation round. The expected number was 152, which gives a proportional interval cancer rate of 0.34. The sensitivity was 86% and the specificity 94% after the first round.

DISCUSSION

The detection rate of breast cancer was high, especially in the prevalence round. The trend in the incidence of breast cancer at the subsequent rounds was similar to that before screening, which indicates that mammography screening does not lead to any greater over-diagnosis. The rate of false positive mammography was high at the initial screening round, but was acceptable at subsequent rounds, and a false positive mammography does not seem to have affected participation in subsequent rounds. The Copenhagen screening programme conforms to international quality assurance guidelines for process evaluation.