Observations on Invasive Breast Cancer Diagnosed in a Service Screening and Diagnostic Breast Imaging Program

Six-hundred six cancers were found among 59,899 woman who had been screened in the Breast Imaging Division at the Massachusetts General Hospital (MGH) from 1990 to 1999 (427 invasive breast cancers detected by screening mammography and 179 invasive breast cancers detected by nonmammographic criteria in women who had previous negative mammograms), and 204 invasive breast cancers were identified during this period solely by nonmammographic criteria in women who had never been screened at MGH but who received a diagnostic mammogram after the time of cancer detection. The screen-detected invasive breast cancers in the MGH data set tended to be smaller, with a median size of 10 mm, than tumors detected by nonmammographic criteria, which had a median size of 15 mm (P 0.001). The mammographically detected invasive breast cancers found in the past decade tended to be slightly smaller than the mammographically detected invasive breast cancers reported by others in previous decades, and the nonmammographically detected invasive breast cancers in the MGH data set were markedly smaller than the nonmammographically detected invasive breast cancers reported in the past. [