Hot Flushes on Tamoxifen: Should I Take Fezolinetant (Veoza)?

11 Oct

She'd read about it online — a new tablet for hot flushes that isn't a hormone — and she came into my clinic with one question. "Should I take fezolinetant?"

She's 54. Two years ago she had a small breast cancer: 15 millimetres, grade 2, invasive ductal, oestrogen and progesterone receptor positive, HER2 negative, with no lymph nodes involved. She had a lumpectomy, a sentinel node biopsy and radiation, and then she started tamoxifen. And since then — the flushes, the brain fog, the anxiety.

This could possibly also be you. You might be on tamoxifen, or on letrozole or anastrozole. You might have heard the word fezolinetant for the first time, and wondered why we haven't talked about it.

We did talk about fezolinetant. We talked about the other medications that can help, too. But we also talked about whether tamoxifen was worth taking for her. And I saw her again recently in clinic, so I'll tell you what she decided.

I'm a breast surgeon and menopause specialist in Wellington, and I look after women with breast cancer and menopause. So this is what fezolinetant is, whether it's been tested in women with breast cancer, what it costs here in New Zealand, the other options, what tamoxifen and the aromatase inhibitors actually do for you, how I worked out her own numbers — and what she decided.

Watch the video

Hot Flushes on Tamoxifen: Should I Take Fezolinetant (Veoza)? Breast Surgeon Explains

This post is the written version of my video. If you'd rather watch, it's all there — the trials, the New Zealand costs, the other options, and the calculation I did with her, on screen.

Watch on YouTube →

Why the flushes happen

Think of your brain's thermostat with its tolerance turned down to almost nothing.

Deep in your brain there's a small group of cells that decides what counts as too hot, and oestrogen sets how wide that comfortable band is. With plenty of oestrogen, the band is generous. Your core temperature drifts up and down and nothing happens. In women without flushes, that band has been measured at about 0.4°C wide. In women with flushes, it's close to zero (Freedman and Krell, 1999).

So a tiny rise in temperature, one that used to be nothing, crosses the line, and your body throws everything at cooling down. Every blood vessel near the skin opens at once, which is the heat up your chest and neck. Then the sweat. Then the shiver.

It's the thermostat, not the fire. It isn't your hormones surging.

On tamoxifen there's a twist. Tamoxifen blocks the oestrogen receptor rather than removing the oestrogen. The aromatase inhibitors — letrozole, anastrozole, exemestane — take oestrogen lower, and faster, than a natural menopause does. Either can bring the flushes on, and how bad they are varies a lot from one woman to the next. In the big trial that compared anastrozole with tamoxifen, flushes were actually a little less common on anastrozole (ATAC).

The cells that run the thermostat talk to each other with a messenger called neurokinin B. When oestrogen falls, those cells get louder, and the neurokinin B signal is what sets the flush off.

A flush is a thermostat set too tight. And there's a messenger behind it that we can now switch down directly.

What fezolinetant is

Fezolinetant is a tablet that turns down the signal that starts a flush. It blocks the receptor neurokinin B acts on, called the NK3 receptor. It isn't a hormone, and it doesn't touch oestrogen at all — which is why women with breast cancer are so interested in it.

It's one tablet a day, 45 milligrams, sold as Veoza, or Veozah in the United States.

What it does

In the two big trials, called SKYLIGHT 1 and 2, women started out having about 10 or 11 moderate to severe flushes a day. At 12 weeks, the women on fezolinetant were having about 2.5 fewer a day than the women on placebo, and the difference was already showing in the first week or so.

Two and a half fewer a day makes a difference. It doesn't make the flushes stop.

The liver

In the trials, about 2 in 100 women on fezolinetant had a rise in their liver tests, against about 1 in 100 on placebo, and it settled when they stopped. After it came onto the market there were rare reports of serious liver injury, and in December 2024 the US regulator, the FDA, added a boxed warning (FDA).

So if you take it, you need a liver blood test before you start, and regular ones after that. The US label asks for one every month for the first three months, and then at six and nine months. I usually check monthly for the first three months, and then every three months.

Your other tablets

Fezolinetant is broken down by a different liver enzyme from tamoxifen, called CYP1A2, so it isn't expected to interfere with tamoxifen or with the aromatase inhibitors. It can't be taken alongside strong blockers of that enzyme — the one you're most likely to meet is fluvoxamine, an antidepressant.

Why treating flushes matters after breast cancer

After breast cancer, a hot flush isn't only a comfort problem.

In one large real-world study of women having flushes on tamoxifen or an aromatase inhibitor, about 2 in 3 had them badly enough to count as moderate or severe — and about 1 in 3 of those weren't getting any treatment for them (REALISE, 618 women in the US and Europe). Flushes are also one of the reasons women stop their tamoxifen or aromatase inhibitor early.

And I understand why women don't raise it. Sometimes women feel like they have to give it everything to treat the cancer, and put up with everything that comes with it. And sometimes they feel they can't tell us these things, because we'll ghost them and not listen — or, even worse, ignore them when they do.

Do the flushes last forever? For most women, no. They're usually at their worst in the first few months, and then they can settle as the thermostat adjusts. But some women are still having bad flushes at year two or three, like my patient.

Treating the flushes helps women keep taking the treatment.

Has it been tested in women with breast cancer?

That was her next question. Not yet. Not properly.

The big fezolinetant trials left out women who'd had breast cancer. There's a larger study, called DAYLIGHT, of women who couldn't take HRT, and that could include women who'd had breast cancer — but it hasn't reported how many of them had, so we can't pull an answer out of it for you.

The trial that will answer it is called HIGHLIGHT 1, in women with hormone receptor positive early breast cancer who are on tamoxifen or an aromatase inhibitor. There are smaller ones too. FLASH-Breast is still running, and another, called VENT, was stopped because it couldn't recruit enough women. As I write this, none of them has reported results, and HIGHLIGHT 1 isn't expected to report until somewhere between 2027 and 2028.

So in New Zealand, and everywhere else, using fezolinetant after breast cancer is off-label. That doesn't mean it's wrong. A lot of what we prescribe for flushes after breast cancer is off-label. It means we're relying on evidence from other women and assuming it carries across.

Elinzanetant, the one that has been tested

A very similar drug has been tested in women like my patient. Elinzanetant, sold as Lynkuet, blocks the same NK3 receptor, and a second one as well.

The OASIS-4 trial included 474 women on endocrine therapy for breast cancer, and just over half of them were on tamoxifen. They started at about 11 flushes a day. At 12 weeks, the women on elinzanetant were having about 3.5 fewer a day than the women on placebo, and their sleep improved too (Cardoso et al, NEJM 2025).

Side effects were common — headache, sleepiness, tiredness. But there were no liver problems, so it doesn't need the blood tests, and it isn't expected to interfere with tamoxifen.

One caution with both drugs. If you're on a CDK4/6 inhibitor, ribociclib for example, there are interactions, so check this with your medical oncologist.

And neither of them helps with brain fog, anxiety, or sleep problems that aren't being driven by night sweats.

In New Zealand

Neither fezolinetant nor elinzanetant is approved here yet. Your doctor can still prescribe them as an unapproved medicine, under what's called Section 29, and certain pharmacies can get them in. Neither is subsidised, so you pay the full cost, and it varies between pharmacies.

Elinzanetant costs over $1,000 a month in New Zealand. That's expensive, to drop three or so flushes a day. For fezolinetant, I'm not sure of the exact cost here. In Australia it's about $75 for 30 tablets, on a prescription — but an Australian pharmacy can't fill a New Zealand prescription.

Where you live changes this

United States. Fezolinetant was approved in 2023, and the boxed warning on the liver was added in December 2024. Elinzanetant was approved in October 2025 for menopause, and in September 2026 the FDA agreed to a priority review of it for women on endocrine therapy for breast cancer.
United Kingdom. Fezolinetant was approved in December 2023. Elinzanetant was approved in July 2025, and in 2026 its licence was extended to hot flushes caused by endocrine therapy after breast cancer.
Europe. Fezolinetant was approved in December 2023.
Australia. Fezolinetant was registered in February 2024.

The other options

After all of that, my patient had another question. Is there anything else that can help with these?

There are other options, and some of them work well for some women.

Without a tablet

Cognitive behavioural therapy has the best evidence of any non-medication option. It doesn't stop the flushes, but it changes how much of your day and your night they take up, and how much they affect you. In New Zealand it's expensive, and it has to be self-funded.

Then there are the practical things that help some women: a cooler bedroom, layers you can take off, and avoiding alcohol.

Non-hormonal tablets

None of these was invented for flushes. Each was developed for something else and then found to calm the thermostat. All of them are subsidised in New Zealand.

Venlafaxine is used most often, usually at a lower dose than for depression, and it can work within a week or two.
Gabapentin, taken in the evening, suits women whose worst problem is night sweats.
Clonidine isn't that helpful.
Oxybutynin, a bladder drug, does surprisingly well in trials, but it comes with a dry mouth.

In my own practice, my patients have preferred venlafaxine or oxybutynin the most. I only have one patient on gabapentin. On average, these tablets probably cut flushes by roughly as much as fezolinetant did in its trials — though that's comparing different trials, not the drugs side by side.

Paroxetine and fluoxetine need to be avoided when you're on tamoxifen, because they block the enzyme in the liver, called CYP2D6, that switches tamoxifen on.

Supplements

Most haven't beaten placebo in trials. Part of that is because supplements aren't standardised or regulated like medicines, so some don't contain the amount they claim to. If you're going to look at supplements, look at your diet first, see what you might be missing, and take only that. Don't take extras — they haven't been shown to work, and they're often quite expensive.

Changing the endocrine therapy

For some women, changing from tamoxifen to an aromatase inhibitor, or the other way round, or from one aromatase inhibitor to another, changes the side effects.

What tamoxifen and the aromatase inhibitors actually do

Which brought us to the question my patient asked next. "Can you remind me again why I take tamoxifen?"

Endocrine therapy — tamoxifen or an aromatase inhibitor — is one of the most effective treatments we have for oestrogen and progesterone receptor positive breast cancer.

The best evidence comes from the Oxford overview, which pooled the trials of tens of thousands of women. For oestrogen receptor positive breast cancer, five years of tamoxifen cut the rate of the cancer coming back by about half during those five years, and by about a third in the five years after that. It cut deaths from breast cancer by about a third, and that benefit lasted out to 15 years (EBCTCG, Lancet 2011).

For women past the menopause, the aromatase inhibitors do better again. Compared with tamoxifen, they cut the chance of the cancer coming back by about another third while you're taking them, and deaths from breast cancer at 10 years by about another 15%. Compared with no tablet at all, that's about 40% fewer deaths from breast cancer (EBCTCG, Lancet 2015).

And in those trials, five years did better than one or two. That matters for my patient, who'd had two.

Now the limit, and it's the important one. These are relative numbers. Cutting the risk in half means half of whatever your risk was to begin with. A lot of the women in those older trials had larger cancers and positive lymph nodes, so their starting risk was much higher than hers.

So she asked me: what's my own risk of dying from breast cancer?

Her own numbers

This is what I did with her in clinic, and what I'd do with you if you were my patient. I used Predict Breast, a calculator we use every day in breast clinics, in its newer 2024 version.

I put in what we knew about her. She was 52 when she was diagnosed, and postmenopausal. Her cancer was oestrogen and progesterone receptor positive, HER2 negative and Ki-67 negative. It was 15 millimetres, grade 2, found on screening, with no lymph nodes involved and no spread. She'd had radiation, and we looked at five years of hormone therapy.

Over 10 years, her survival with surgery alone came out at 95%. Adding radiation, still 95%. Adding the hormone therapy, 96%.

And that's out of 98, not out of 100 — because over those ten years, about 2 women in 100 like her would die of something else, a heart attack or a car crash.

So for her, five years of tamoxifen added about 1%. Out of 100 women like her who take it, about 1 will be alive at ten years because of it. The other 99 get no survival benefit from it — most of them because they'd have been fine anyway.

What that number doesn't tell you

It's an estimate built from many thousands of women, not a prediction for the one woman in front of me. In clinic I say it's a number out of a hundred women like her. We don't know which of those hundred she is.
It's built mostly on British data, but we use it every day in our clinics in New Zealand.
It compares five years with none. It doesn't answer "what if I stop at two years?" She'd already had two years, and she keeps some of the benefit from those.
It's about survival — being alive at ten years. The chance of the cancer coming back is a different number, and tamoxifen usually does more for that one.

What she decided, three months ago

She decided to stop tamoxifen, at least for a bit. To see how she is off it. Is her quality of life better or not? Is it just menopause, or is it tamoxifen plus menopause? Are her symptoms worse on tamoxifen or not? We didn't know. But we made a plan to catch up in three months, to see how she actually was.

So what's important here? It's extremely important that she felt she could talk to me about it — that she could get the knowledge and the support from me, and then make her own decision.

And it's the same for you. I want you to be able to have the same with your doctors: good discussions, looking at all your options and the benefits, and then making the decision you think is best for you.

You are entitled to it.

Please don't stop your endocrine therapy on your own and tell nobody. Talk to your doctors, or find someone who will listen and support you in your treatment plan. A different tablet in the same family, a switch, a break that's been planned rather than one that happened because it felt like there was no other option — we can't really help you with any of that if we don't know how much you're struggling.

When to ring

Most of what you're feeling on these tablets is the treatment doing what it does. A few things are not.

The emergency department, now

New breathlessness, chest pain, or a calf that's suddenly painful and swollen on one side. Tamoxifen raises the risk of blood clots. The risk is very small, but it's there, and this one doesn't wait. Ring 111, or go straight to the emergency department.

When you call, say:

"I'm on tamoxifen for breast cancer, and I've got chest pain."

Or a swollen leg. That sentence puts you in the emergency queue.

A phone call to your GP or breast team today, not tomorrow

Any vaginal bleeding after the menopause while you're on tamoxifen. Tamoxifen thickens the lining of the womb, and it needs to be checked.
If you're on fezolinetant: yellowing of your skin or the whites of your eyes, dark urine, or pain under your ribs. These are the signs of liver problems. The tablet needs to stop, and it needs to be checked.

A call in the next day or two

Flushes so bad that you're thinking of stopping the tablet.
A new low mood or anxiety that arrived with the tablets.

What she decided when I saw her again

So, three months later, what did she decide?

Her flushes were less severe. She was sleeping a bit better, with less brain fog and less anxiety. Those symptoms were still there, but they weren't having such an impact on her. So, on the balance of things, she decided to stop tamoxifen permanently.

That was her decision, with her numbers. Yours might be different.

What to write down, and what to ask

Here's what I'd like you to take from her story into your own.

If you're having these symptoms, work out how bad they are. How many flushes do you have in 24 hours? How bad is your anxiety? How bad is your brain fog, your sleep? Give each one a score, say out of five. That page turns "they're quite bad" into "eleven a day, and my anxiety is four out of five". And then we have a reference point. We know how bad it is.

Then take these three questions to your next appointment:

"Which non-hormonal options suit me, and do any of them interact with my tamoxifen?"

"Is fezolinetant or elinzanetant an option for me, and what would it cost me?"

"What is my own risk, and how much are these tablets doing for me, out of a hundred women like me?"

That last one is the one my patient asked me. It's the question most women never ask, and most women should.

If there's something here I haven't answered, or something you were told about your flushes that didn't sound right, put it in the comments under the video. I read them, and they're where the next videos come from.

You have time. Ask the question. Then make the decision yourself.

The video