Arimidex vs. Tamoxifen

My 1.4 cm tumor was both Her2 and ER positive (neg lymph nodes).  I am premenopausal, age 42.  I have completed lumpectomy and chemotherapy, will begin radiation therapy next week, and need to understand the advantages/disadvantages of Arimidex (sp?) versus Tamoxifen. One oncologist recommends Tamoxifen, the other Arimidex.  I understand there is some controversy as to the effectiveness of Tamoxifen on Her2 positive, premenopausal women.  Would appreciate additional information about studies, findings, etc. on the comparative effectiveness of these therapies for women such as myself.  Also, my oncologist wants to delay the therapy until after I complete the radiation. Any risks in doing that?  Thanks very much for your help.

[CCF-RN,MSN-rf]

Dear Rene01:  Aromatase inhibitors are not yet approved for adjuvant treatment.  They are approved for advanced disease only.  In addition, aromatase inhibitors are for post-menopausal women.  At this point, if you are not in a clinical trial for herceptin, tamoxifen would be the best option.  Tamoxifen is given after chemotherapy but can be given either with or after  radiation at the physician's discretion.