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 tbe 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 rum at FFDM and 13 mm at SFM. Including cancers dismissed at consensius 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.