Randomized trial of screen-film versus full-field digital mammography with soft-copy reading in population-based screening program: follow-up and final results of Oslo II study.

PURPOSE: To prospectively compare performance indicators at screen-film mammography (SFM) and full-field digital mammography (FFDM) in a population-based screening program.

MATERIALS AND METHODS: The regional ethics committee approved the study; informed consent was obtained from patients. Women aged 45-69 years were assigned to undergo SFM (n=16 985) or FFDM (n=6944). Two-view mammograms were interpreted by using independent double reading and a five-point rating scale for probability of cancer. Positive scores were discussed at consensus meetings before decision for recall. The group was followed up for 1.5 years (women aged 45-49 years) and 2.0 years (women aged 50-69 years) to include subsequent cancers with positive scores at baseline interpretation and to estimate interval cancer rate. Recall rates, cancer detection, positive predictive values (PPVs), sensitivity, specificity, tumor characteristics, and discordant interpretations of cancers were compared.

RESULTS: Recall rate was 4.2% at FFDM and 2.5% at SFM (P<.001). Cancer detection rate was 0.59% at FFDM and 0.38% at SFM (P=.02). There was no significant difference in PPVs. Median size of screening-detected invasive cancers was 14 mm at FFDM and 13 mm at SFM. Including cancers dismissed at consensus meetings, overall true-positive rate at baseline reading was 0.63% at FFDM and 0.43% at SFM (P=.04). Sensitivity was 77.4% at FFDM and 61.5% at SFM (P=.07); specificity was 96.5% and 97.9%, respectively (P<.005). Interval cancer rate was 17.4 at FFDM and 23.6 at SFM. The proportion of cancers with discordant double readings was comparable at FFDM and SFM.

CONCLUSION: FFDM resulted in a significantly higher cancer detection rate than did SFM. The PPVs were comparable for the two imaging modalities.