[weety]

Okay, one more possible theory to throw into the barrel:

In some early lab (not human) experiments, Herceptin caused ER- tumors to change to ER+ tumors. I pretty much dismissed this at first because of it not being tested in actual humans. However, in doing more research the other night, I found a trial that is actively recruiting right now to see if this actually happens in real people. The trial is giving one dose of Herceptin to ER negative gals before their surgery and then rechecking estrogen receptors after surgery to see if hormonal status has changed. I don't have the exact link to the study, but I think I found it on the clinicaltrials.org or .com? site.

Thinking through it, though, I don't know if this could explain much in the study we're discussing, because as someone else pointed out, herceptin wasn't standard during the years they looked at.