Overdiagnosis and overtreatment of breast cancer.

Breast cancer is the most common cancer in women. Through greater awareness, mammographic screening, and aggressive biopsy of calcifications, the proportion of low-grade, early stage cancers and in situ lesions among all breast cancers has risen substantially. The introduction of molecular testing has increased the recognition of lower risk subtypes, and less aggressive treatments are more commonly recommended for these subtypes. Mammographically detected breast cancers are much more likely to have low-risk biology than symptomatic tumors found between screenings (interval cancers) or that present as clinical masses. Recognizing the lower risk associated with these lesions and the ability to confirm the risk with molecular tests should safely enable the use of less aggressive treatments. Importantly, ductal carcinoma in situ (DCIS) lesions, or what have been called stage I cancers, in and of themselves are not life-threatening. In situ lesions have been treated in a manner similar to that of invasive cancer, but there is little evidence to support that this practice has improved mortality. It is also being recognized that DCIS lesions are heterogeneous, and a substantial proportion of them may in fact be precursors of more indolent invasive cancers. Increasing evidence suggests that these lesions are being overtreated. The introduction of molecular tests should be able to help usher in a change in approach to these lesions. Reclassifying these lesions as part of the spectrum of high-risk lesions enables the use of a prevention approach. Learning from the experience with active surveillance in prostate cancer should empower the introduction of new approaches, with a focus on preventing invasive cancer, especially given that there are effective, United States Food and Drug Administration (FDA)-approved breast cancer preventive interventions.