Reference: JAMA. 2024 Apr 30 early online
Practice Point: The USPSTF joins the majority pack of professional organizations recommending mammography for breast cancer screening starting at age 40.
EBM Pearl: Consideration of the unintended harms of our good intentions is a critical component when identifying appropriate parameters for population-based screening interventions.
A Doximity email came out last week alerting clinicians to the 2024 USPSTF final recommendation reducing the age to initiate mammography for breast cancer screening from 50 to 40 for those at average risk. The headline was followed by a short summary and then…a comment thread. If you are an EBM enthusiast who values your sanity and normal heart rate, do yourself a favor and don’t read the comments. Almost exclusively, those moved to remark were in favor of earlier screening as though it were a no-brainer, with many endorsing an ‘earlier the better’ philosophy. A fair number of commenters openly asserted that prior USPSTF recommendations to begin screening at 50 were influenced by cost and politics, not evidence or clinical reasoning. Not a single comment even hinted at the idea of overdiagnosis or overtreatment. While some argue that the updated USPSTF recommendation for all will primarily benefit a subset of the population, a proper debate would involve discussions about equity, values, opinions about societal priorities, and of course, evidence. Since this is the EBM Focus, we’d like to zoom in on a small but often overlooked part of the picture: the harms of overdiagnosis and overtreatment that can result from a population-based screening intervention.
Remember - when we talk about screening, we mean doing something to an asymptomatic person in order to detect a disease for which treatment at a preclinical stage will result in a longer or better life than if the disease were detected and treated after symptoms develop. Screening is sometimes recommended based on objective risks (known genetic mutations, tobacco exposure), or can be based on subjective or socially-determined risks (race/ethnicity, geography, profession). When we propose an intervention for asymptomatic people, the burden of proof for clinical benefit is high. We must demonstrate beyond a reasonable doubt that the benefits of our proposed intervention outweigh the potential harms. And we must consider all the possible harms, even the iatrogenic ones. In the case of breast cancer screening, evidence clearly suggests that waiting until age 50 to screen Black female patients results in lives lost and perpetuates health disparities. To those with the good intention of saving lives (and a bias towards action), the answer seems clear and uncomplicated - screen everyone sooner. However, balancing the relative harms of action and inaction is difficult and messy.
Just as inaction can be harmful, every intervention has the potential to cause unintended harms. For breast cancer screening, the harms go much deeper than anxiety created by false positives, healthcare costs of screening programs, and patients who are unable to get life insurance because of their breast cancer diagnosis. We’re talking death from screening. Here’s how: because our screening methods are imperfect, increased screening for breast cancer inevitably results in the detection of additional breast cancers that will never progress to clinical disease. But because early breast cancer (and in particular DCIS) is highly unpredictable, we can’t always know which tumors will progress and which won’t. More diagnoses inevitably result in more treatment, which can save some people’s lives, but also may contribute to death or other morbidity in others. Said more directly, screening can lead to iatrogenic suffering and death in people who would not have died from their cancer had it gone undetected. These harms must be accounted for when evaluating the risks and benefits of an intervention, and are an important reason why discussions (and decisions) should have a weighted focus on all-cause mortality, not simply disease-related deaths. The USPSTF transparently and systematically evaluated the evidence using this lens and concluded that at a population level, the balance of benefits and harms lies in favor of earlier screening for all. While valid arguments can still be made in either direction, and whether a population-based recommendation is right for the patient in front of you, this updated recommendation communicates a lot more nuance and depth than can be found in a comment thread.
For more information, see the topic Breast Cancer Screening in DynaMed.
DynaMed EBM Focus Editorial Team
This EBM Focus was written by Katharine DeGeorge, MD, MS, Senior Deputy Editor at DynaMed and Associate Professor of Family Medicine at the University of Virginia. Edited by Alan Ehrlich, MD, FAAFP, Executive Editor at DynaMed and Associate Professor in Family Medicine at the University of Massachusetts Medical School; Dan Randall, MD, MPH, FACP, Deputy Editor at DynaMed; Nicole Jensen, MD, Family Physician at WholeHealth Medical; Vincent Lemaitre, PhD, Medical Editor at DynaMed; Hannah Ekeh, MA, Senior Associate Editor at DynaMed; and Jennifer Wallace, BA, Senior Associate Editor at DynaMed.