Letrozole or Tamoxifen, which should I choose?

Letrozole is an aromatase inhibiter. It shuts off oestrogen from your fat cells, which is the only place it is still produced post-menopausal (that's how I understand it anyway). There are 3 AIs, so if you didn't get on with one, you could swap.

They started me on an ovary suppression implant during chemo so that I would be post-menopausal by the time I started exemestane.

It's funny how we all react to things differently - I never liked the sound of the tamoxifen side effects!

It's less scary than you think - I was really worried about starting hormone therapy, more so than chemo, but it does settle. They said to me about 6 months for the worst side effects to settle down and it was about that. It's hard to tell what is a side effect of the medication and what is just menopause symptoms.

I have extensive experience of both Letrozole and Tamoxifen, having had Tamoxifen first time round (fourteen years ago, just before menopause), and tried all the Aromatase Inhibitors (AIs) like Letrozole, now I've had a recurrence well after menopause.

Aromatase Inhibitors (AIs) work by completely blocking any production of oestrogen, so there's none to 'feed' any remaining, or new, oestrogen-positive breast cancer cells. They block the aromatase enzyme, which converts the small amounts of testosterone we have, into oestrogen. Post menopause this is the only oestrogen we have - it's a very small amount, but makes a big difference. So losing it all does have quite an impact on the system, in my experience. However, there is research that shows that patients' perceptions of AI ageing effects are worse than the reality.

Personally, I find the notorious arthralgia (joint pain) the worst symptom, though hair thinning and further vaginal atrophy are also not fun (try an internal moisturiser like Replens). I could do without the increase in hot flushes, too. I'm not surprised that quite a large percentage of breast cancer patients give up on AIs.

I have actually tried all three AIs available at the moment. I found very little difference between Letrozole and Anastrozole; Exemestane is slightly different as it is steroidal, but again, it seemed no better than Letrozole. And as Exemestane costs the NHS around £90 per month, but Letrozole costs around £10 per month, I decided I would stick with the Letrozole.

BUT I am planning to switch to Tamoxifen after three years of AIs, to give myself a break from the negative side-effects of AIs. Tamoxifen doesn't completely prevent the production of oestrogen, but it does stop any cancer cells from binding with it, so they can't use it for growth. I was on it for five years, fourteen years ago, when I had my first bout of cancer (my current treatment is for a new primary recurrence). I got on well with it, much better than AIs, but it carries a slightly increased risk of endometrial cancer, and nearly always thickens the uterus (I ended up with a D&C to remove a large number of polyps, after two years, and had a few more removed over the following three years). So I will have gynae monitoring alongside the oncology monitoring.
I have discussed alternating 6 months of Tamoxifen, then 6 months Letrozole, to try and avoid the uterine side-effects of Tamoxifen. Letrozole has a half-life of 90 days, so it will take quite a long time before I can assess whether the AI symptoms have improved or gone, but even a few months' relief from the negative AI symptoms would be good.

What interesting comments. Is Tamoxifem as effective as exemestane and letrozole? I have had a hysterectomy am wondering why it was never suggested to me. My osteoarthritis after nearly 5 years is horrendous plus horrible weight gain etc my oncologist suggested I could stop the exemestane but as I have only a few months to go I am hanging on.

Hope you don't mind all the questions, just saw your post by chance x

For post menopausal women , there are studies that show that AIs are more effective at preventing recurrence than tamoxifen . Which is why they ask you to try to persevere with them . 

Hi Rozalia. If you've had a radical hysterectomy (so removal of ovaries as well as uterus) I guess that will have made you post-menopausal, whatever your age. In which case the go-to post-breast cancer meds would be AIs (Aromatase Inhibitors).

From what I understand from research, AIs (like Letrozole and Exemestane) are slightly more effective than Tamoxifen in preventing a beast cancer recurrence (though there's not a lot in it, they just work in different ways, see above). And as you're pretty near the end of your stint on them I suspect it would be good if you could hang on in there and complete the Exemestane course. I think the half-life on Exemestane is shorter than Letrozole, so you should get back to normal quite quickly once you stop this endocrine therapy. However, it's always best to check with your oncologist.

Mine is quite flexible, and sympathetic to my AI side-effects (I also had a small, grade 2 tumour that was contained locally, no lymph node involvement) - so he's agreeable to me being on Tamoxifen instead, even though I am post-menopausal. I have family history of cancer of the uterus (my late mother), hence my concern about the thickening uterus effects of Tamoxifen, and why I think I'd be best alternating it with an AI, so I'm just getting a 6-month break from the arthralgia each year.

However, I may find that even off the AIs, age has caught up with me and a lot of it is actual arthritis symptoms - in which case I'll stick with the Letrozole; I won't know until I try. In my case I'm keen to avoid a knee replacement, if it turns out that half the symptoms are down to the AIs.

These days, medics like you to be on the endocrine therapy for anywhere between 5 and 10 years, but, like several of the people who have responded on this thread, there's a balance to be struck between quality of life, and side-effects - partly depending on your age.

I hope your own symptoms ease up once you've completed your meds x

Many thanks Kif x

Many thanks, Michelle. I was post memo pause when I started A!s.  I kept my ovaries post-hysterectomy and must say I had a relatively easy menopause. I got cancer coming up to 70 and the effects of the AI beat the menopause, worst is the weight gain and increased osteoarthritis. I am now looking at knee replacements and ankle fusion. I had osteoarthritis before cancer but it has significantly worsened.  I am wondering if it will improve when I stop the AIs this summer. The waiting lists mean I am unlikely to get the ankle fusion before August and I will need this whatever but the knees will be at least 6 months afterwards and who knows maybe I won't need them by that time. But I think the damage is probably already done! Hopefully, the weight will go and that should ease the pressure on my joints. I hope you manage to avoid knee operations. I can't walk very well but I do aqua exercise 5 days a week, which has helped my flexibility. 

Many thanks for your detailed answer. I found what you had to say very informative x

Hormone treatment reduces recurrence risk. Side effects are inevitable but tolerable if you think about the alternative - incurable recurrence. Where you draw the line between quality of life and overall survival is very individual, it’s something you need to work out over time.

Side effects are not inevitable. There are many people who have no issues at all from hormone therapy. I guess it depends on the type prescribed, as well as all kinds of other factors, but it’s not a certainty that someone will experience side effects.

Just putting my 10pence worth in here, although I am not on Tamoxifen, (though there’s time yet) my mum was, nearly 35/40 years ago after her first breast cancer diagnosis, she already had a hysterectomy in her late 20’s. She survived on tamoxifen for years, and finally aged 80 was diagnosed with bladder cancer, and a year later metastasis from breast cancer reoccurrence. So it kept her free for a long time, and we have a very strong history of (female) cancer, breast mainly but ovarian and blood cancer in my family. The same can be said for her cousin who had a more aggressive breast cancer in her 30’s, who is still with us at 86 years old. I think we have to expect side effects and try and cope with them the best we can, I’m certainly not looking forward to them, but will try my best.