"Because the cumulative incidence among controls never reached that of the screened group, it appears that some breast cancers detected by repeated mammographic screening would not persist to be detectable by a single mammogram at the end of six years," the authors write. "This raises the possibility that the natural course of some screen-detected invasive breast cancers is to spontaneously regress."
"Although many clinicians may be skeptical of the idea, the excess incidence associated with repeated mammography demands that spontaneous regression be considered carefully," they continue. "Spontaneous regression of invasive breast cancer has been reported, with a recent literature review identifying 32 reported cases. This is a relatively small number given such a common disease. However, as some observers have pointed out, the fact that documented observations are rare does not mean that regression rarely occurs. It may instead reflect the fact that these cancers are rarely allowed to follow their natural course."
The findings do not answer the question of whether mammograms prevent deaths from breast cancer, the authors note. "Instead, our findings simply provide new insight on what is arguably the major harm associated with mammographic screening, namely, the detection and treatment of cancers that would otherwise regress," they conclude.
Editorial: Results Emphasize Our Lack of Knowledge Regarding Cancer's Natural History
"Despite the appeal of early detection of breast cancer, uncertainty about the value of mammography continues," write Robert M. Kaplan, Ph.D., of the University of California, Los Angeles, and Franz Porzsolt, M.D., Ph.D., of Clincal E
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