Please refer to the article I posted in this link
http://her2support.org/vbulletin/sho...eferrerid=1173
wherein the designers of the trial considered tamoxifen to be such a potent up regulator of Her2, that they suggest all future trials of tamoxifen should include a Her2 inhibitor, regardless of the Her2 status of the subject.
The seminal discussion on this issue began in the 20 year retrospective of the Naples GUN trial in 2003:
http://clincancerres.aacrjournals.or.../9/3/1039.full, with the discovery that Her2 positive women who received only tamoxifen fared more poorly than Her2 positive women who recieved no further treatment. The authors found the use of chemotherapy to be confounding to reaching a clear conclusion on the matter. As more research is conducted, it is becoming more apparent that there is an exposure (as yet unquantified) to using tamoxifen treatment in some Her2 positive patients.
On a side note, it is my personal belief that Oncotype Dx, which calculates a recurrence score based on the assumption that the patient receives no treatment other than adjuvant tamoxifen, artifically inflates the scores of Her2+ patients based on the GUN results described above. Think about it - if you are doing a test for the purpose of calculating likelihood of recurrence by comparing the outcome of the subject based on that subject receiving a specific treatment, in relation to other subjects who had been given the same treatment which has been shown to induce recurrence, rather than prevent it, well - what kind of score would you expect to see? I would like to see this issue addressed by Genomic Health, the inventor of the Oncotype test.
Hopeful
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