The question of whether the non HRT users had more advanced disease is answered by this precaution. They were each at similar stages when diagnosed and all were recurrence free at the point that the study measured from. There seem to be no possible explanations for this surprising result. However, it seems strange that a group of 174 women were given HRT after breast cancer when the same doctors decided not to administer this treatment to the other 2,581. Not all breast cancer is triggered by estrogen.
Some cancers have a negative estrogen receptor status.
If these women were in that group, then the administration of estrogen to them would not have increased the risk of recurrence. Their tumors would not have responded to the estrogen. Until this data can be examined more closely the conservative approach seems justified. The fact that in these cases the doctors treating them felt safe giving them HRT when they decided against this treatment in thousands of similar situations seems suspect. It makes all the difference in the world to the interpretation of the results.