CHARACTERISTICS OF BREAST-CANCER IN AN INCIDENT CANCER POPULATION

The effectiveness of film mammography is a source of concern to radiologists because neither the ribs nor retromammory space is included on the films in good quality examinations. Incident cancers (107) were detected in 10,034 self-referred women followed at the University of Michigan Breast Cancer Detection Demonstration Project (UM-BCDDP [Ann Arbor, Michigan, USA]) for 5 yr. These cancers were analyzed for location on the film, method of detection, size, histology and the number of films required for detection. Mammography alone detected 52 (49%) of the cancers, whereas physical examination alone detected 15 (14%). The other 40 cancers were detectable on both examinations. All of the 92 cancers detected by mammography were visible in both the mediolateral and the craniocaudal views. Only 2.2% of these cancers were within 1 cm of the posterior edge of the film in the mediolateral view; 18.7% were within 1 cm of the posterior edge in the craniocaudal view. These incident cancers were smaller and fewer were located within the posterior 1 cm of the breast than in a similar study using the UM-BCDDP prevalent cancer population. Mammography consistently detected cancer in the breast, regardless of tumor size, histologic type, or location within the breast.