Will Early Detection for Breast Cancer Ever Work?

Abstract

The fundamental challenge for those who advocate for screening and early detection of breast cancer is that breast cancer is not a single disease. It is a collection of heterogeneous diseases, ranging from those that grow slowly and pose little risk, to diseases with the potential for metastatic spread, even at a very early stage. To understand how to refocus early-detection efforts in breast cancer, it is important to examine the trends in cancer incidence since the introduction of widespread screening mammography. Routine screening mammography in the US has produced an increase in the detection of early-stage disease, particularly in situ (stage 0) and early-stage (stage 1) cancers. Despite the considerable increase in the detection of ductal carcinoma in situ (DCIS), there has not been a proportional concomitant decline in the incidence of early-stage invasive cancers, which is what one would expect if DCIS were an obligate precursor to invasive breast cancer. Similarly, the overall incidence rates of stage 2 and 3 cancers have shown only a small decline over the last 20 years, despite the overall significant increase in the detection of in situ and early-stage cancer. This finding suggests a bias toward the detection of indolent rather than aggressive cancers (1, 2). This trend is particularly worrisome because the goal of screening is to prevent lethal, progressive disease by detecting cancer at an earlier, more treatable stage, or by detecting precursor lesions that can be removed before they develop into lethal invasive cancers. Yet epidemiologic data suggest that screening has substantially contributed to an increase in the detection of early-stage disease that may have little chance of progressing or becoming lethal over the course of a person's lifetime. The original notion behind screening, based on the excellent survival rate for stage 1 cancers, was that targeting removal …