Study Reinforces That Mammography Detects Breast Cancers Earlier, Saves Lives
WASHINGTON, DC -- October 12, 2016 -- A study published in the New England Journal of Medicine clearly shows that mammography screening catches more cancers early and reduces the number of women with cancers of advanced size.
The data do not support the authors’ conclusion that improved therapy is more key to breast cancer survival than mammography screening. Nor does the data support that mammography use leads to rampant over-diagnosis.
The National Cancer Institute’s Surveillance, Epidemiology and End Results (SEER) database used by the authors does not provide the detailed information needed to support such claims. The baseline assumption on which the conclusions are based is contradicted by the primary author’s previous papers and well-established research.
The current study reiterated the SEER database finding that there has been a 30% decrease in large tumours found in American women after screening became widespread. This major decline in large tumours is related to the documented increase in the detection of small invasive cancers.
Not surprisingly, the same SEER database shows that since mammography screening proliferated in the mid-1980s, the US breast cancer death rate, unchanged for the previous 50 years, has dropped nearly 37%. This is in keeping with large studies (Otto et al. and Coldman et al.) that have shown that in women who get regular mammograms, the risk of dying from breast cancer is cut nearly in half.
As a primary baseline for their calculations, the authors claim that annual growth in invasive breast cancer incidence was flat at 0% in years preceding the start of screening in the United States. This differs from a previous paper by Welch et al., which claimed the incidence growth rate to be .25% annually. Both claims are unsupported. Accounting for the real underlying incidence of invasive breast cancer is important, as shown by Puliti et al., and based on actual patient data is just over 1% per year from 1940 to the start of the SEER program in 1974. Had the authors used the actual 1% breast cancer incidence growth rate, the findings would have been vastly different -- showing no evidence of over-diagnosis and a marked decline in advanced cancers, which has led the decline in breast cancer death since screening began.
Given this significant flaw, it is not surprising that the current study’s conclusions are debunked by a recent study in the British Medical Journal, which confirmed that early detection of breast cancer via mammography is critical for improving breast cancer survival, regardless of therapy advances. Numerous other studies show that even when women have access to the latest therapies, deaths from breast cancer decline at a much higher rate in women who get mammograms.
Despite differing guidelines by the American Cancer Society, the United States Preventive Services Task Force (USPSTF), National Comprehensive Cancer Network (NCCN), the American College of Radiology (ACR), and the Society of Breast Imaging (SBI), all groups agree that the most lives are saved by annual screening beginning at age 40.
Given these facts, the ACR and SBI continue to recommend that women start getting annual mammograms at age 40 and continue to do so as long as they are in good health.
SOURCE: American College of Radiology
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