Amelia,
Here is a link to a thread that contains several excellent links on this topic:
http://her2support.org/vbulletin/sho...eferrerid=1173
I agree with Katie's remarks above completely when she says, "oncologists are generally resistant to this idea of tamoxifen resistance in Her2+ patients - at this point the available data hasn't reached a critical point to change standard of care for Her2+ patients," and would add that those of us on this Board do a pretty good job of staying ahead of the curve in terms of reading papers and studies that apply to Her2+ patients, and often are the ones who bring this information to the attention of our doctors. IMO, it is always wise to keep asking questions until you get answers that make sense.
Hopeful