Breast cancers detected by mammography screening do not spontaneously disappear or regress if left untreated, according to a new study published in the Journal of the American College of Radiology. The scientific findings contradict claims that many cancers found via mammography may simply "go away" if left undiscovered or untreated.
Among all practices involved in the study, 25,281 screen-detected invasive breast cancers and 9,360 cases of screen-detected ductal carcinoma in situ were reported over the 10-year study period. Among these cancers, there were 240 cases of untreated invasive breast cancer and 239 cases of untreated ductal carcinoma in situ. None were reported to have spontaneously disappeared or regressed at next mammography.
An unknown percentage of these 479 cases represent overdiagnosis, but because all untreated screen-detected cancers were visible and suspicious for malignancy at next mammographic examination, delaying the onset of screening (from age 40 to ages 45 or 50) or increasing the interval between screenings (biennial vs annual) should not reduce the frequency of overdiagnosis.
Medical science cannot yet determine which cancers will or will not advance to kill the person afflicted.