The first 20 years of the Dutch population-based mammography breast cancer screening program have contributed to a drop in deaths from the disease while limiting screening harms such as false positives and overdiagnosis, according to study results reported at the Eighth European Breast Cancer Conference (EBCC-8) in Vienna.

Between 1989 and 2009, 16.6 million personal invitations to screening were sent to 3.6 million women aged 50 to 75, according to the study abstract. Compared with the three years prior to the program, deaths from breast cancer among women aged 55 to 79 fell by 31 percent in 2009, according to Jacques Fracheboud, MD, a senior researcher from Erasmus University Medical Center in Rotterdam, The Netherlands.

“We found there was a significant change in the annual increase in breast cancer deaths: before the screening program began, deaths were increasing by 0.3 percent a year, but afterwards there was an annual decrease of 1.7 percent,” Fracheboud said in a statement. “This change also coincided with a significant decrease in the rates of breast cancers that were at an advanced stage when first detected.”

The screening was rolled out in three phases: implementation for women aged 50 to 69 occurred from 1989 to 1997, screening was extended to women up to age 75 in 1998, and a transition from film screen to digital mammography was made in 2004, according to the abstract. Overall attendance was 80 percent, increasing from 73.4 percent in 1990 to 81.5 percent in 2009. During the study period, 13.2 million screening exams were performed among 2.9 million women for an average of 4.6 exams per woman.

Screening resulted in referral recommendations in 1.35 percent of cases and biopsies in 0.72 percent of cases. Referral rates increased by approximately 200 percent in initial screenings and by approximately 100 percent in subsequent screenings, resulting in an increase of detection rates by more than 30 percent. There were a total of 66,562 breast cancer diagnoses.

Screening harms were limited due to low rates of false positives and overdiagnosis. For a woman who was 50 years old at the start of the program, there was a six percent risk of a false-positive result over the 20-year period. Detection of tumors that would never progress to become a problem was limited to 2.8 percent of all breast cancers diagnosed in the total female population and 8.9 percent of screen-detected breast cancers.

The total annual cost of the program was €51.7 million ($68.3 million) in 2009, or €56.65 ($75) per examination, which, when adjusted for inflation, is approximately €3.50 ($4.6) less than in 1996.

“We are convinced that the benefits of the screening program outweigh all the negative effects,” said Fracheboud. “These results may also be of value for other mammography breast cancer programs that are strictly population-based, centrally organized, where quality assurance is guaranteed and that are continuously monitored and evaluated.”

Implementation of the breast cancer screening program was based on experience from two pilot programs and an extensive cost-effectiveness analysis. The results presented at EBCC-8 were largely in line with predictions from 1990, according to Fracheboud.