Purpose: To investigate the positive predictive value for cancer of abnormal mammographic findings and the role of assessment procedures.
Materials and methods: We reviewed a series of 962 patients recalled and examined in the 1st Breast Screening Center of Turin, out of 18; 996 women aged 50-59 screened for the first time from 1991 to 1995, within a population-based mammography program. The diagnostic assessment procedures included one or more of the following: physical examination, additional mammographic views (detail or magnification), ultrasonography, and ultrasonography/X-ray-guided fine needle aspiration cytology. Surgical biopsies detected 152 cancers.
Results: The positive predictive value for screening mammography with abnormal findings steadily grew from 10.9% in 1991-92 to 15.6% in 1993, topping 21.1% in 1994 and 20.1% in 1995. The highest positive predictive value for cancers was observed among cases referred for opacities with irregular margins (88.2%) and isolated calcifications (23.8%). The benign/malignant biopsy ratio was .54 in 1991-92, .31 in 1993, .27 in 1994 and .25 in 1995. The accuracy of assessment procedures was different for each abnormal radiologic sign: the accuracy of cytology was high for opacities, intermediate for calcifications, low for architectural distortions; ultrasonography and physical examination had low sensitivity among cases referred for calcifications or opacities with regular margins. The positive predictive value of surgical indications was high for opacities, intermediate for calcifications, low for architectural distortions. The role of assessment procedures in excluding surgery was different for each abnormal radiologic sign.
Discussion and conclusions: The results of this study confirm the accuracy of mammography in the early detection of breast cancer and the different role of assessment procedures in the various abnormal mammographic findings. The improvement in positive predictive value for screening recalls from about 10% (close to recommended European standards) up to about 20% (well above European standards) demonstrates the importance of the "learning curve" within the screening team. Most of this improvement could be referred to refined diagnostic criteria for calcifications, as shown by an increase in positive predictive value for calcifications from 13.7% in 1991-92 to 40.5% in 1995.