ER premenopausal

I am 35 years old who had a er+/pr+ tumor. I have been on tamoxifen since September 01. I was not getting my periods for 6 months then in November and December got them. My oncologist said I should take this drug to stop my period. Will a run a greater risk of reoccurence I continue to get periods and not take the drug?  I thought tamoxifen was supposed to stop periods.
Thanks

[CCF-RN,MSN-rf]

Dear hooves:  Tamoxifen is a SERM (selective estrogen receptor modulator) drug.  This means that in some organs (the breast) estrogen is blocked.  In other organs, such as the uterus, estrogen levels are actually higher.  This helps to explain why the incidence of uterine cancer in women taking tamoxifen is higher.  Although, many women do develop amenorrhea (absence of menstrual period), it is not uncommon for premenopausal women to have periods.  It is also technically possible for a woman to become pregnant while taking tamoxifen, although this is certainly not recommended.  A non-hormonal form of birth control should be used by women who are taking tamoxifen.  Tamoxifen has shown benefit in terms of recurrence and preventing new breast cancer on the opposite side in women with estrogen receptor positive tumors.  This is true even in premenopausal women.  It is very important to maintain your annual pelvic and PAP smear.  You should also let your physician know if you experience any abnormal bleeding.

[MPM]

I hadDCIS and now the doctors are suggesting tamoxifan (tamoxifen).  I am scared to go on it but I don't want the cells to come back.  DCIS is not tested for ER so I'm not sure why I should take it.  What stage of cancer did you have and what did you do to remove it?  Are you having bloating? mood swings, hot flashes