it is possible that my memory of the issue is warped a bit because when i went to find some studies i first found a leaflet from a danish research center that makes clear that the problems with mammograms are not so much in that they cause cancer, but that they result in a statistically significant amount of mis-diagnosis. mis-diagnosis results in healthy women having breasts removed and chemotherapy un-necessarily..
Thus mammograms do increase the risk of death and it is claimed actually statistically do much more harm than good:
http://nordic.cochrane.org/sites/nordic.cochrane.org/files/public/uploads/images/mammography/mammography-leaflet.pdf