Untreated Breast Cancers Do Not Regress, Researchers Say

Untreated breast cancers detected on screening mammography do not spontaneously disappear or regress, according to a study published in the Journal of the American College of Radiology. Researchers from New York, Texas, Missouri, and California performed a prospective cohort study to investigate the natural history of untreated screen-detected breast cancer to determine if there was validity in claims that breast cancer is over-diagnosed with regular screening and that some of these cancers would regress or disappear if left untreated. The researchers received completed surveys from 42 Society of Breast Imaging fellows in December 2016, with outcomes data from their screening mammography practices.  The results showed among all practices, 25,281 screen-detected invasive breast cancers and 9,360 cases of screen-detected ductal carcinoma in situ were reported over the past 10 years. Among these cancers, there were 240 cases of untreated invasive breast cancer and 239 cases of untreated ductal carcinoma in situ, among which zero were reported to have spontaneously disappeared or regressed at next mammography. The researchers concluded among the 479 untreated breast cancers detected on screening mammography, none spontaneously disappeared or regressed. They acknowledged an unknown percentage of these cancers represent over-diagnosis, but because all untreated screen-detected cancers were visible and suspicious for malignancy at next mammographic examination, delaying the onset of screening or increasing the interval between screenings should not reduce the frequency of over-diagnosis.