Medical Oncologist
Medicines
How long will you be on anastrozole?
Most women with early hormone-receptor-positive breast cancer take anastrozole for about five years, sometimes after a few years of tamoxifen. Some are advised to continue longer when the chance of the cancer returning is higher. This page explains the usual plans, what shapes the decision to extend, what is still uncertain, and what happens when you finish.
NG
Medically reviewed by Dr. Naresh GunduConsultant Medical Oncologist · MBBS, DNB (Internal Medicine), DM (Medical Oncology, AIIMS) · last reviewed September 2026, next review due September 2027
On this page
- How long is anastrozole usually taken?
- Four ways anastrozole fits into a treatment plan
- What shapes the decision at the five-year mark
- The vocabulary, in plain language
- What is still uncertain about treatment length
- Getting ready for the conversation about stopping or continuing
- What happens when you finish anastrozole
- What people assume about how long anastrozole is taken
- Common questions about how long to take anastrozole
The short answer
How long is anastrozole usually taken?
For early hormone-receptor-positive breast cancer after menopause, anastrozole is most often taken once a day for five years. That length comes from large trials that compared five years of anastrozole with five years of tamoxifen and found anastrozole lowered the chance of the cancer coming back a little more. Not everyone starts on it, though. Some women begin with tamoxifen, often because they were still having periods at diagnosis, and then change to anastrozole after two to three years so that the total time on hormone tablets is about five years. Others finish five years of tamoxifen and then take anastrozole for a further period. For women whose cancer carried a higher chance of returning, such as cancer in several lymph nodes, doctors may suggest carrying on beyond five years. How much extra time helps is still being worked out. One large study of anastrozole found that adding two more years after the first five protected about as well as adding five more years, and caused fewer broken bones. So the length is a balance between the small extra protection and the side effects that continue, especially bone thinning. Anastrozole is also used for five years to lower the risk of breast cancer in some high-risk women, and after treatment for DCIS. In advanced breast cancer there is no fixed end date: it continues while it keeps the cancer controlled. Please do not shorten the course on your own.
Five years is the common plan
Most early breast cancer plans are built around five years of hormone therapy in total.
Longer is a case-by-case decision
Extra years are weighed against your original risk, your bones and how you have coped.
Advanced cancer has no set length
When cancer has spread, anastrozole is taken for as long as it keeps working.
This page gives general information only. Your oncologist will advise on the length of treatment that is right for you.Common plans
Four ways anastrozole fits into a treatment plan
The length of your course depends on why you are taking it and what came before.
Five years from the start
Many women who are clearly past menopause take anastrozole straight after surgery, chemotherapy or radiotherapy, and continue for five years.
Following tamoxifen
If you began on tamoxifen, your doctor may switch you to anastrozole after two to three years, or add anastrozole after five years of tamoxifen to extend protection.
Your doctor must be sure your ovaries have stopped working before the switch.Risk reduction and DCIS
Some women at high risk of breast cancer, or treated for DCIS, are offered anastrozole for about five years to lower the chance of a new cancer.
Advanced breast cancer
Anastrozole may be taken alone or with a targeted tablet such as ribociclib, palbociclib or abemaciclib, and continues until the cancer grows or side effects become too hard.
Reasons the plan may change
- Scans show the cancer is growing
- New symptoms caused by the cancer
- Side effects that cannot be managed
Weighing it up
What shapes the decision at the five-year mark
Factor
Which way it usually leans
Cancer had spread to several lymph nodes
Towards some extra years of hormone therapy
Small, low-grade, node-negative cancer
Towards stopping after five years
Osteoporosis or a past fracture
Towards stopping, or continuing only with bone protection
Joint pain or other side effects affecting daily life
Towards stopping, or switching to a different tablet
Your own wishes and priorities
A shared decision with your oncologist
Words you will hear
The vocabulary, in plain language
- Adjuvant hormone therapy
- Hormone tablets taken after surgery and other main treatment to lower the chance of the cancer returning.
- Extended therapy
- Carrying on with hormone tablets beyond the usual five years.
- Sequential or switch treatment
- Taking one hormone tablet for a few years, then changing to another to complete the plan.
- Late recurrence
- Breast cancer that returns more than five years after it was first treated.
- Risk reduction
- Using a medicine to lower the chance of breast cancer in someone at high risk.
- Treatment break
- A planned pause in tablets, agreed with your doctor for a specific reason.
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Being straight with you
What is still uncertain about treatment length
You may find that doctors give slightly different advice about how long to continue. That is because the evidence is still developing, especially for women at moderate risk.
The first five years matter most
Most of the benefit of hormone therapy comes from the first five years. Extra years add a smaller amount of protection, which is worthwhile for some women and not for others.
More years mean more bone loss
Anastrozole keeps oestrogen very low, which thins bones over time. Each extra year has to be weighed against that, particularly if your bones are already thin.
No test gives a clear answer
Some genomic tests aim to estimate the risk of late return, but they are not routinely used to decide treatment length and are not available everywhere.
What this page cannot tell you
It cannot decide how long you should take anastrozole. Only your oncologist, with your full history and reports, can advise on that.
Planning ahead
Getting ready for the conversation about stopping or continuing
As you near the end of your planned course, ask for a proper discussion rather than simply renewing the prescription. A little preparation helps you and your doctor reach a clear decision together.
Find your original reports
Your pathology report shows tumour size, grade, lymph node involvement and receptor status. These details carry the most weight in the advice you receive.
Check your bones
A recent bone density scan shows whether more years of very low oestrogen are likely to be safe, or whether bone treatment would be needed alongside.
Describe your daily life honestly
Tell your doctor how joint stiffness, hot flushes, sleep, mood and intimacy have been. These are real parts of the decision, not complaints to hide.
After the last tablet
What happens when you finish anastrozole
Many women feel relieved to finish, and some feel anxious, because the daily tablet felt like a safety net. Both feelings are normal.
Side effects usually settle
Joint aches and hot flushes often ease over the following weeks to months. Bone density may recover a little once oestrogen returns to its usual post-menopausal level.
Protection carries on
Research shows the benefit of hormone therapy continues for years after the tablets stop, so finishing does not mean the protection vanishes.
Follow-up continues
You will still have regular check-ups and mammograms, and you should keep reporting any new symptoms between visits.
Commonly believed
What people assume about how long anastrozole is taken
Everyone takes anastrozole for exactly five years.
Five years is common, but some women switch partway and others continue for longer.
Ten years is always safer than five.
Extra years give less added benefit when risk is low, while bone loss and side effects continue.
If my scans are clear, I can stop early.
Scans cannot see tiny cancer cells. The full planned course is what gives the protection.
Stopping the tablets wipes out the benefit.
The protective effect of hormone therapy lasts well beyond the years you take it.
Questions we are asked
Common questions about how long to take anastrozole
Is five years of anastrozole enough for me?
For many women, five years gives most of the benefit. Your oncologist may suggest longer if your cancer had features linked with a higher chance of returning later, and if your bones and side effects allow it. The answer depends on your own reports and health.
Does my time on tamoxifen count?
Yes. Doctors usually count the total years on hormone therapy. If you took tamoxifen for two or three years before switching, anastrozole normally completes a five-year plan rather than starting a new five years, unless extended treatment is recommended.
Can I take a break from anastrozole?
Unplanned breaks are best avoided, because protection depends on keeping oestrogen low. A pause may be agreed for particular reasons, such as severe side effects. Speak to your oncologist before stopping, even for a few weeks, so the plan stays safe.
I stopped for several months. What now?
Tell your oncologist honestly. Restarting is usually advised, and your doctor may adjust the overall length. Many people find long courses hard, and your team would much rather know and help than have you continue struggling alone.
How long is anastrozole taken for advanced cancer?
There is no fixed end point. It continues while scans and symptoms show the cancer is controlled and side effects are acceptable. When it stops working, your doctor will talk to you about the next treatment, such as fulvestrant or another combination.
Do side effects get worse over the years?
Not usually. Hot flushes and joint stiffness often improve somewhat after the first year, although bone thinning continues slowly. Regular bone checks and vitamin D help manage this over a longer course.
Can I change tablets instead of stopping?
Often, yes. Some women who struggle with anastrozole manage better on letrozole, exemestane or tamoxifen, and this can help them finish their planned years. A short break before trying another tablet is sometimes suggested. Ask your oncologist which option fits you.
Who makes the final decision about stopping?
It is a shared decision. Your oncologist explains the likely benefit of continuing and the risks to your bones and quality of life, and your own views carry real weight. You are welcome to ask for time to think it over.
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Sources
- American Society of Clinical Oncology — Hormonal therapy for early-stage hormone receptor-positive breast cancer
- Breast Cancer Now — Anastrozole (Arimidex)
- National Cancer Institute — Hormone therapy for breast cancer
This page is general information, not a prescription. Do not change or stop any treatment based on what you read here. If anything is worrying you, contact your own treating team — or call our helpline and we will help you reach the right specialist.