blood clot risks

My onc just called and told me that new studies have shown that Tamoxifen can be of benefit even to women with very low estrogen receptor percentages.  I was 3%ER and 5%PR.  I am stage IIa, N0, M0.  I have already undergone a lumpectomy, 18 weekly treatments of Taxol and 36 treatments of radiation.  I am only 40 so if this is true about Tamoxifen, I would like to try it.  However, my father and his mother and brother have all suffered with thrombo-phlebitis and I'm just not sure about the risks.  Exactly what is the risk percentage and how much more at risk am I?   And how much benefit will I really get from taking Tamoxifen?  Is it worth it?
Thanks,
Shari

[CCF-RN,MSN-JS]

Dear Shari, The risks of blood clots with Tamoxifen are very low about 2%, this risk increases with age (over 50).  I do not know about your blood clot risk just based on your family history, there may be more individual factors causing these problems in your family members - I couldn't say.  There have been studies demonstrating up to 49% risk reduction in women who are at high risk of developing cancer (this is in women who have never had cancer).  The risks and possible benefits of tamoxifen for your individual situation is best discussed with your oncologist.