INITIAL VERSUS SUBSEQUENT SCREENING MAMMOGRAPHY - COMPARISON OF FINDINGS AND THEIR PROGNOSTIC-SIGNIFICANCE

OBJECTIVE. The goal of this study was to compare findings on initial a nd subsequent screening mammograms to determine the prognostic signifi cance of screening-detected abnormalities. MATERIALS AND METHODS, All 3386 abnormal examinations from a 9-year mammographic screening progra m were studied, An initial examination was defined as one for which th ere were no prior films available for comparison (even if one or more prior examinations had been performed); the remainder were called subs equent examinations, The principal mammographic feature of each abnorm ality was recorded, as well as whether a biopsy was performed, For all screening-detected cancers, we also determined several surrogate mark ers of prognosis (tumor size, presence of axillary lymph node metastas is, and tumor stage). These various parameters were analyzed as a func tion of initial versus subsequent screening. RESULTS. The frequency of abnormal examinations was more than 2 times greater for initial exami nations (7%) than for subsequent examinations (3%). Only minor differe nces were noted between initial and subsequent screenings when compari ng the principal mammographic features of the abnormalities, However, the number of cancers found per number of biopsies performed was signi ficantly greater (p=.02) for subsequent screenings (41%) than for init ial screenings (32%). Among the 333 cancers detected, tumor size was s ignificantly smaller for subsequent screenings (p=.0076), Node-negativ e status and early tumor stage (stage 0 or 1) also were found more fre quently for subsequently screened cancers, but these differences were not statistically significant CONCLUSION. Substantially fewer abnormal screening interpretations are made when mammography has been performe d previously and when the prior films are available for comparison. Th is results in cost savings and reduced morbidity at subsequent screeni ng (no further work-up, less patient anxiety, fewer benign biopsies). Surrogate markers of prognosis also appear to be more favorable for ca ncers detected at subsequent screening.