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The original goal of mammographic screening was to identify invasive cancers at the earliest stage, because of the superior prognosis of stage I cancers. Prior to the advent of screening, ductal carcinoma in situ (DCIS) made up approximately 3% of breast cancers detected. As we pushed to find smaller and smaller cancers, and targeted calcifications instead of just masses, we began to identify DCIS more frequently. Now DCIS accounts for approximately 20% to 25% of screen-detected breast cancers. The cells that make up DCIS look like invasive cancer both pathologically and molecularly, and therefore the presumption was made that these lesions were the precursors of cancer and that early removal and treatment would reduce cancer incidence and mortality. However, long-term epidemiology studies have demonstrated that the removal of 50 000 to 60 000 DCIS lesions annually has not been accompanied by a reduction in the incidence of invasive breast cancers.1 This is in contrast to the experience with removal of colonic polyps and intraepithelial neoplasia lesions of the cervix, in which the removal of precursor lesions has led to a decrease in the incidence of colon and cervical cancer, respectively.2 We now know that breast cancer encompasses a range of behaviors, from aggressive to indolent; the latter are more likely to surface with screening.3 The analysis of Narod et al4 fuels a growing concern that we should rethink our strategy for the detection and treatment of DCIS.
Esserman L, Yau C. Rethinking the Standard for Ductal Carcinoma In Situ Treatment. JAMA Oncol. 2015;1(7):881–883. doi:10.1001/jamaoncol.2015.2607
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