Effective breast cancer detection with film-screen mammography.

Non-visualization of the retromammary space and ribs has been a source of concern to mammographers. In six years, 186 cancers were detected in our experience of 10 034 self-referred asymptomatic women at the University of Michigan Breast Cancer Detection Demonstration Project. These cancers were used to analyze the need to visualize the retromammary space and ribs, or both sites, if adequate technical factors were used. All the cancers were analyzed for position on the film, number of films required for visualization, relationship of the tumor to the posterior edge of the film, number of occult tumors, tumor size, histologic type, sensitivity of detection method and the number of interval cancers. Of the 186 cancers, 168 (90%) were detected on mammograms. All of the cancers were visualized on the mediolateral view; three were not visualized on the craniocaudal view. Six per cent of the cancers were within 1 cm of the posterior edge of the film; the remaining 94% were located more anteriorly in the breast. The imaged tumors were smaller and had a significantly higher percentage of non-invasive cancers than found in a symptomatic clinical population. Therefore, mammography, using proper technique, will consistently permit visualization of cancer in the breast, regardless of tumor size, histologic type, or location in the breast.