Four Principles to Consider Before Advising Women on Screening Mammography

Abstract

This article reviews four important screening principles applicable to screening mammography in order to facilitate informed choice. The first principle is that screening may help, hurt, or have no effect. In order to reduce mortality and mastectomy rates, screening must reduce the rate of advanced disease, which likely has not happened. Through overdiagnosis, screening produces substantial harm by increasing both lumpectomy and mastectomy rates, which offsets the often-promised benefit of less invasive therapy. Next, all-cause mortality is the most reliable way to measure the efficacy of a screening intervention. Disease-specific mortality is biased due to difficulties in attribution of cause of death and to increased mortality due to overdiagnosis and the resulting overtreatment with radiotherapy and chemotherapy. To enhance participation, the benefit from screening is often presented in relative instead of absolute terms. Third, some screening statistics must be interpreted with caution. Increased survival time and the percentage of early-stage tumors at detection sound plausible, but are affected by lead-time and length biases. In addition, analyses that only include women who attend screening cannot reliably correct for selection bias. The final principle is that accounting for tumor biology is important for accurate estimates of lead time, and the potential benefit from screening. Since “early detection” is actually late in a tumor's lifetime, the time window when screen detection might extend a woman's life is narrow, as many tumors that can form metastases will already have done so. Instead of encouraging screening mammography, physicians should help women make an informed decision as with any medical intervention.

Given Overdiagnosis, Recall Reduction Should Trump DCIS Detection

“…A systematic review of overdiagnosis, controlled for confounding biases, shows that the frequency of overdiagnosis (invasive cancer and DCIS) is only 1%-10% (3). Furthermore, with use of extrapolation based on observed outcomes rather than estimates, screening actually yields fewer than expected invasive cancers (1,4), refuting Drs Keen and Jørgensen's self-professed contention that this has not occurred (7,8). Drs Keen and Jørgensen make many misstatements.…”

“…However, Saadatmand et al (6) clearly state that they did not evaluate breast screening, and their observation that stage at diagnosis is closely linked to prognosis is insufficient evidence that early detection in breast cancer is "vital." The same link exists for other types of cancer, that is, neuroblastoma and thyroid cancer, where early detection through screening is clearly not beneficial (7). Indeed, the premise that detecting early stage breast cancers leads to fewer late stage breast cancers is questionable (5).…”

A suggested framework for conducting esophageal cancer screening in China

“…Lead‐time bias occurs when screened participants are thought to live longer than their unscreened counterparts. Rather than having longer survival, screened patients seemingly live longer merely because their disease is detected before symptoms occur . Consequently, lead‐time bias overestimates screening benefits.…”

“…Rather than having longer survival, screened patients seemingly live longer merely because their disease is detected before symptoms occur. 52 Consequently, lead-time bias overestimates screening benefits. While it is a challenging task, evaluating the parameter distribution by comparing the clinical incidence of screened and unscreened participants could help reduce the computing deviations caused by lead-time.…”

Opportunity cost of annual screening mammography

“…Recall rates from US insurance claims data already are between 13% to 19%, which is higher than the Breast Cancer Surveillance Consortium data used in the CISNET models . Decreasing the US false‐positive rate from 15% to 10% would save at least $1.3 billion annually, which is enough to treat 25,000 women with invasive cancer .…”