Hormone-blocking therapy for metastatic breast cancer

For people with hormone receptor-positive metastatic breast cancer, hormone-blocking therapy helps to shrink or slow the growth of their cancer.

Usually, you take the drugs for as long as they work. When one hormone-blocking therapy stops being effective, you may change to:

• another hormone-blocking therapy or
• another type of treatment altogether.

Which hormone-blocking treatment is right for you?

The treatment your oncologist recommends will depend on several factors. These include:

• which hormone-blocking therapies you have taken previously (for example, after a previous diagnosis of early breast cancer)
• whether you were still taking a breast cancer hormone-blocking therapy when metastatic breast cancer was diagnosed
• whether you are premenopausal (still having periods) or if blood tests show your ovaries are still producing oestrogen
  whether you are postmenopausal (your periods have stopped) and your ovaries are no longer producing oestrogen.

If your metastatic breast cancer is HR+, your oncologist will advise you to stop using:

• hormone replacement therapy
• hormonal contraceptives.

Menopause and hormone-blocking therapies

If your menopausal status is unclear – for example, you’ve had a hysterectomy or your periods stopped during chemotherapy – your doctor may suggest a blood test to check your hormone levels. Then they can discuss the options with you.

Options for first line therapy

‘First line’ treatment is the first hormone-blocking therapy you take for metastatic breast cancer. You continue to take your first line treatment until:

• it is no longer working or
• side effects mean you can’t continue.

You may move on to a ‘second line’ hormone-blocking therapy or another treatment altogether.

First line therapy for premenopausal women

It is common for premenopausal women to have treatment to ‘shut down’ the ovaries and bring on menopause. This is ovarian suppression or ovarian treatment.

You will also be recommended an anti-oestrogen hormone-blocking drug.

Some hormone-blocking drugs, such as the aromatase inhibitors and fulvestrant, only work if your ovaries are not producing oestrogen.

Treatment that results in temporary menopause

If you are having goserelin (Zoladex) injections, menopause is only temporary. As long as you continue the injections you are classed as postmenopausal. You can have therapies suitable for postmenopausal women. Once you stop the injections, you may become premenopausal again.

Treatments that result in permanent menopause

If your ovaries are removed (‘oophorectomy’) or you have radiation treatment to your ovaries, you will become permanently postmenopausal. Your hormone-blocking therapy will be the same as for postmenopausal women.

No ovarian suppression

Your cancer may be very slow growing and causing minimal problems. If you are on hormone-blocking drugs such as tamoxifen (Nolvadex) or toremifene (Fareston), you do not need to be postmenopausal for them to work. Sometimes doctors will recommend ovarian suppression as well, even though they are effective without it. Ovarian suppression and a hormone blocking drug is called 'dual-endocrine therapy'.

First line therapy for postmenopausal women

The recommendations depend on whether or not you were taking hormone-blocking therapy when metastatic breast cancer was diagnosed.

If you were not taking hormone-blocking therapy

If you have not taken hormone-blocking therapy before, or your last one was more than 12 months ago, your options may be:

• aromatase inhibitor on its own – either anastrozole (Arimidex), exemestane (Aromasin) or letrozole (Femara)
• aromatase inhibitor plus CDK4/6 inhibitor
• tamoxifen – sometimes recommended if you or your oncologist prefer this option or because of concerns about the side effects of an aromatase inhibitor.

If you were taking an aromatase inhibitor

The options if you were taking an aromatase inhibitor at the time of your diagnosis include:

• Aromatase inhibitor plus CDK4/6 inhibitor –  this combination proved very successful in clinical trials and is listed on the PBS.
• Exemestane (aromasin) – this has a different chemical structure from the other aromatase inhibitors. It can be effective after anastrozole or letrozole stop working.
• Tamoxifen – this is a good option, especially if you have never taken it before or it is some years since you were on it. It may not be suitable if you have history of deep vein thrombosis (DVT) or a clot in the lungs (pulmonary embolus).
• Fulvestrant – an effective option on its own, as well as in combination with a targeted therapy such as a CDK4/6 inhibitor.

If you were taking tamoxifen

Treatment options include:

• an aromatase inhibitor (anastrozole, exemestane, or letrozole)
• an aromatase inhibitor plus CDK4/6 inhibitor
• Zoladex if you are also premenopausal.

Second line therapy

If your cancer progresses, or the side effects of treatment are affecting your quality of life, your medical oncologist may suggest a change.

The medication you take as a second line therapy depends on what you have previously taken. It could be:

• a different hormone-blocking therapy alone or with a targeted therapy
• a chemotherapy or targeted chemotherapy (an 'antibody drug conjugate')
• a clinical trial.

You continue on your second line treatment as for first line treatment, as long as:

• the cancer remains controlled 
• you're not having side effects that affect you too much.

Your oncologist will try to continue hormone-blocking therapies for as long as possible. Third and even fourth line treatments may be possible once treatments stop being effective.

Over time – often several years – you will probably be treated with many different therapies.

Side effects

People taking hormone-blocking therapy for metastatic breast cancer may experience a range of side effects. Some people don’t have any side effects.

Find out about Side effects and how to reduce them.