Letrozole and Menopause

I am 53 and have been on Tamoxifen for 3 years.  Prior to Tamoxifen, I didn't have full periods (only spotted a little) since I had an endometrial ablation over 10 years ago.  I haven't had a period (or spotting) since starting the Tamoxifen.  However, I responded to Tamoxifen with high estradiol levels and ovarian cysts.  I was put on Lupron for 6 months at first and after the ovarian cysts returned, I was on it for a year.  My last shot was Aug 2003.  My hormonal levels in October showed that my ovaries were still active.  This last month my hormone levels [FSH (25.7) and estradiol (23)] showed that I was in the menopausal region but barely.  Since recent studies have shown improved survival for those who switch to letrozole, I am anxious to be menopausal and make the switch.  Also since the "lack of period for a year" standard doesn't work for me in determining if I'm menopausal, what values should I be looking for before I can safely make the switch?

[CCF-RN,MSN-JS]

Dear ritaav, The recent study regarding the switch from tamoxifen to letrozole was in women that had completed 5 years of tamoxifen treatment for their breast cancer.  Current data does not support the switch to letrozole prior to completing the full five years of tamoxifen therapy, although their are clinical trials exploring this question.  

The levels that would particularly be evaluated would be the FSH, LH, and estradiol levels.  There is not a specific number that is looked at but more the ratio of FSH to LH.  Research suggests that a high serum FSH to LH ratio (1.9-3.8) may be a useful indicator of menopausal status. The above levels are evaluated along with physical changes and age to determine a person's menopausal status.