premise: (Last year about 60,000 in the United States got a D.C.I.S. diagnosis.) One piece of evidence is that the women who had mastectomies had their entire breast cut off and so , <hypo> for women who had lumpectomies that could have left D.C.I.S. cells behind..
hypothesis: <hypo> should be "their death rate should have been lower than it was"