Breast Cancer Screening: Is There Room for De-escalation?

Abstract

Purpose of review: Breast cancer screening is highly controversial and different agencies have widely varying guidelines. Yet it is currently used extensively in the USA and frequently the thought is "the more, the better." The purpose of this review is to objectively assess the risks and benefits of screening mammography and consider whether there may be areas where it could be de-escalated.

Recent findings: Over the past few years, there have been several meta-analyses that are concordant, and it is now agreed that the main benefit of screening mammography is about a 20% reduction in breast cancer mortality. This actually benefits about 5% of patients with mammographically detected tumors. We now appreciate that the main harm of screening is overdiagnosis, i.e. detection of a cancer that will not cause the patient any harm and would not have ever been detected without the screening. This currently represents about 20 to 30% of screening detected cancers. Finding extra cancers with more intense screening is not always good, because in this situation, the risk of overdiagnosis increases and the benefit decreases. In some groups, the risk of overdiagnosis approaches 75%.

Summary: Our goal should be not only to find more cancers, but to avoid finding cancers that would never have caused the patient any harm and lead to unnecessary treatment. The authors suggest some situations where it may be reasonable to de-escalate screening.

Keywords: Breast cancer screening; De-escalation of breast cancer screening; Harms of breast cancer screening; Overdiagnosis.

Fig. 1

Effect of screening mammography. A The screened group always has an increased number of cancers due to both lead time and overdiagnosis. B This illustration assumes no true reduction in cancer deaths but nevertheless the standard survival curves (deaths/cancer) show a large benefit for screening. Only large population-based studies (deaths/population) can determine whether there is really a benefit for screening

Fig. 2

Natural history of current mammography detected invasive cancers. Recent SEER data showing 20% mortality for invasive tumors were overlayed with the mammography mortality reduction of 20% and the overdiagnosis rate of 25%. Only 5% had a cancer that was cured because of the mammography. This represents a 20% (5/25) reduction in mortality

Fig. 3

Percent overdiagnosis by patient age and tumor biology. Favorable tumors were low grade and ER and PR positive. (From New England Journal Medicine, Lannin DR and Wang S. Are small breast cancers good because they are small or small because they are good? 376(23):2286–2291. Copyright © 2017 Massachusetts Medical Society. Reprinted with permission.)