High oestrogen levels through Tamoxifen

ParisParis

Hello everybody,

I wonder if anybody has some insider knowledge about elevated estradiol levels on Tamoxifen?

After the end of my radiotherapy treatment I started with Tamoxifen around the end of February. I am perimenopausal and had my last menstruation in January, but nothing since taking Tamoxifen.

I am participating in an observational study about the quality of life after early breast cancer, for this I had extensive blood tests done on two occasions, the latest one last week. This test showed extremely elevated estradiol levels, 1260 pg/ml! I was quite shocked, only to be told not to worry - that it is normal on tamoxifen!

I understand that tamoxifen works as an anti-oestrogen in the breast but does not do so in the rest of the body. I do not understand how such high oestrogen levels can be seen as "normal". I hate to imagine how the fibroids in my uterus will be fed by this oestrogen surge (Let's party!) and it must raise the risk for uterine cancer if kept at that level for some time.

I participate in a post-cancer programme and do exercise several times a week to keep oestrogen levels in check - well, that seems quite ironic now! And I remember the fuss one doctor at the hospital made when queried about eating a bit of flaxseed...

I am quite unsure now - does anyone know if oestrogen levels will stay so high? Because if they do, I wonder if I should stay on Tamoxifen. I entered my data into the NHS Predict tool and 5 years of tamoxifen give me only a marginal survival benefit - 0.6% after 5 years and 1.4% after 10 years!

Thank you for your thoughts!

gb2115

No insider knowledge, but I did read what you said when investigating how tamoxifen works, how the tamoxifen is anti-estrogen for the receptors, but doesn't actually lower the estrogen in your body. I get hot flashes only around the time of ovulation, which is when estradiol levels are highest, so I wonder if my levels are through the roof too. But, it's better than getting breast cancer again. My survival benefit (NHS predict) is 1.6 for 5 years and 3.2 for 10 years, so thinking long term, that's enough to convince me to risk it.

My oncologist doesn't seem to concerned about "estrogenic" things like eating soy or drinking alcohol...she has said to be moderate in all things, which really is excellent advice. What is the point of avoiding estrogenic things if you are taking tamoxifen which sends levels through the roof. I dunno.

I just looked at your profile--you and I have been pretty much on the same time frame. I also started Tamoxifen at the end of February, and had my surgery just a few days after you did! I'm like a couple weeks behind you! Similar type of cancer too, except mine was slightly larger and I had that unfortunate positive lymph node. It was even on my right side too. Weird huh?!

ParisParis

Hi, yes, quite a number of similarities! I guess you had chemo, I am so glad I got around it. compared what some people have to go through, I really had " breast cancer light". But It was still scary. I hope you got through everything okay!

I had an appointment for the study today and nobody is bothered by my oestrogen levels, but I have made an appointment with my gynecologist. I want this retested and a proper follow-up. It is annoying, since I did not have any chemo I do not have a medical oncologist and the surgeon or the radio-oncologist are zero interested in hormones.

ChemicalWorld

Don't know if this answers any questions Paris, but my estrogen levels stayed high through Tamoxifen. I was 40 at diagnosis, still having periods regularly, which stopped during chemo, and never came back until I had just one about a year or so later, while on Tamoxifen. The following year a gyno gave me a dose of progesterone to induce a period (because of the endo cancer risks), which happened, and then never another one again.

I was without an MO at the time (the one I'd had through chemo had moved practice across the country), so during a regular follow up with my radiation onc I mentioned all this when the nurse was asking me about my periods, and was referred to a new MO and also a gyno-oncologist pretty quickly. None of them thought it was a good idea that I should have been induced to have a period, and the gyno assumed I was in menopause because I wasn't having any periods.

I had hormone tests done and was told I was still producing loads of estrogen at the time, despite having one spontaneous period in those years following. Which resulted in the Lupron/ooph discussion, and Lupron is where I am now. No one ever hormone tested me since, just the assumption that I'm now chemically menopausal. I've recently switched to arimidex but had remained on tamoxifen for the first few years I've been on Lupron shots.

I have a history of PCOS and had irregular periods at times in the past, and that was the only reasoning they could come up with for me still having such high estrogen levels despite never having a period. No one ever said it was because of the Tamoxifen.

FWIW, despite these high levels, I had an ultrasound about a year or so in and my uterus was fine, no thickening or anything.

ShetlandPony

My estradiol levels were high on tamoxifen, and eventually I had tamoxifen amenhorrea. In other words, my periods eventually stopped but my E2 and FSH levels showed I was not postmenopausal. Tamoxifen can stimualte the ovaries of premenopausal women, causing high estradiol levels and sometimes ovarian cysts. My uterine fibroids grew large while I was on Tamoxifen, and shrank when I went off of it and into permanent chemopause.

The question, of course, is what do you do with this information that your estradiol level is abnormally high? You could ask your onc if there is any recent data on this question. Would you and your doctors consider ovarian suppression or oophorectomy along with the tamoxifen or an aromatase inhibitor? What would be the risks vs. benefits in your case?

Back then I told my doctors I was concerned about the high estradiol levels. The breast surgeon and gynecologists were in favor of an oophorectomy, reasoning that high levels could not be a good thing. But all three medical oncologists said no, all I needed to do was stay on tamoxifen. (When the results of the SOFT trial came out later, they confirmed the oncs' advice.) So I went against my own intuition. Looking back, I wonder if I had a kind of ILC that is tamoxifen-resistant, and so there was just a large amount of estrogen not getting blocked by tamoxifen as expected. I wish I had done the ooph or at least lupron. But we will never know if things would have gone differently or not. Of course, one person's experience should not influence you. And you have IDC, not ILC. But that's my story for what it's worth.

Here is one article that shows how things can vary from woman to woman. "Tamoxifen and Ovarian Function"

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC369599...