Chemotherapy vs. Tamoxifen

I am trying to understand the use of tamoxifen as a systemic treatment.  I understand that chemotherapy can kill cancer cells that may have spread to other parts of the body.  I believe I understand that Tamoxifen prevents cell growth but does not kill cells.  I have read very conflicting reports about this.  I am 35 and was diagnosed with IDC - 1.3 cm tumor ER/PR+; grade 2 and no lymph node or vascular involvement - I had a sentinel node biopsy.  I have had a lumpectomy and am trying to make a treatment decision.  The recommendation from my oncologist is obviously radation, followed by Tamoxifen for 5 years.  If Tamoxifen does not kill cells, what is to prevent their growth once you discontinue taking it?  Thanks for any insight you can provide.

[CCF-RN,MSN-rf]

Dear p406:  Tamoxifen is an anti-estrogen.  It is used to treat women whose breast cancer is estrogen-receptor positive.  It works by depriving the tissue of estrogen, thus preventing tumors that are "fed" by estrogen.  In clinical trials, the use of tamoxifen was given for 5 vs 10 years.  There was no benefit to use of tamoxifen over 5 years.  The question is whether you need chemotherapy - this is also controversial.