Resistant to tamoxifen? Very worried

Hi Ladies - I’ve been taking tamoxifen for almost 8 weeks now and can honestly say the SE’s are absolutely minimal. I’m so worried that i’m not metabolising it. I’ve got an appointment with the oncologist on 31st but in the meantime:

Has anyone purchased the tamoxifen resistance test? (not widely used here and certainly has to be paid for )

If i am resistant is there anything that can be done? I’m thinking not as i undertand tamoxifen “is it” for pre-menapausal women.

Any info would be really appreciated i’m becoming more worried with each passing day - who’d have thought i’d be worried about anything without SE’s!!!


My mild flushes didnt start until i had been on tamoxifen and zoladex for 3 months, and my bcn said it takes this long to fully get into your system.

Hi Lynn
Sorry to hear about your worries, but l agree with lolly, my onc and surgeon told me it would take 3 months before the drugs got fully into our systems, l am due to take Femara, which is post menopausal, but both work in a similar way.
Good Luck and Look forward to you asking how you can get rid of the side effects once they start!!!
Sandra x

I have been on Femera for about 10 weeks now, my onc says its early days ( It is being used to shrink my lump) I can’t see any difference in my lump size but am now having more hot flashes. They are ok really and don’t last very long at all. Very manageable.I don’t think that you can go by SEs to see if things are doing their job, different people react differently. Assume all is well until they tell you otherwise… that’s my ostrich impression. Head in the sand until something changes, it’s hard but it’s kinder to yourself.
x sarah

HI Lynn

Other options could include zoladex injections to shut down ovaries (I think these are done monthly?) or even ovary removal (oophrectomy). However as others have said, it may a bit early. I haven’t heard of the test but unless it is prohibitively expensive it may well be worth the cost if it’s reliable.

take care

I haven’t heard of the test either. When I was being considered for Tam a few months ago I asked my onc as I had read that quite a large group are resistant and I asked whether I could be tested, she said she would enquire - but I never found out as it was then decided that Femara was more suitable anyway. I presume it would be a genetic test, as I understand the resistance is genetic.

Lynn - I think the others are right - you need to give it a little longer and there are definitely other options. Have PM’d you about something else.

finty xx

Hi Ladies,
I started taking Tamoxifen at the end of February and thought I was not going to suffer too much. Ha ha wrong!!! I have got worse and worse hot flushes and am now getting aches and pains in my ankle and shoulder.
Like the other ladies said, it didn’t happen straight away but took several months to kick in.
I haven’t heard of the test either.
Jane xx

Hi Lynn,

I took Tamoxifen and was worried about it didn’t work. I read about the test too and mentioned it to onc. He just said that I’d given Tamoxifen to me anyway regardless of the result of the test! I didn’t notice signs that things weren’t going quite right after 2 months. But the 3 months wait is the standards here. And by the time the scan results came back, I was nearly on it for 4 months. Well, it showed progression and I ended up back on chemo. Very unlucky!

I’ll be given zoladex to shut down my ovary and an Arimidex (I think) now my chemo has finished. I’m pre-menopausal, too. So, Tamoxifen is definitely NOT the only option for us.

Hope all goes well on the 31st xx

Hi Ladies - thanks for your responses. Much appreciated. Lots of you are suggesting its a gradual build up - this is so frustrating!! i asked that very question of the oncologist 2 weeks ago and was told no - “if that’s the very limited side effects you’re getting , then that’s likely to be it” What chance have we got if we don’t get told the same thing!

Similarly i had been told at the beginning that there were other drugs for post menapausal women but none that were effective for pre. (very glad there is )

I didn’t express concern over the lack of SE’s at that time, it was only afterwards i researched that it was potentially an indicator of poor metabolisation - hence the appt for the 31st. Re the resistance test i have attached some links which will need to be copied into your web browser to be opened. Thanks again.


Hi Lynvee
I’m in much the same boat as you and asked these questions earlier this year. The BC nurse (when asked) said this was an indication of resistance to Tam but my Onc said it wasn’t which was v unsatisfactory. I’ve now been taking the Tam for about 8 months and I find I get hot after about 4 hours sleep. It doesn’t come in flushes so not sure if it is the summer weather (but I’m in Scotland!?) or the Tam. I’m like you, hoping for (some) SE’s! V interested if you get any further with this.

Thanks Arrangirl - Yep i’ll be sure to keep you posted after the 31st and yep being in Scotland too i doubt its got anything to do with summer.