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Aromatase inhibitors to lower breast cancer risk | CION Cancer Clinics
Aromatase inhibitors can lower breast cancer risk in some women after menopause who are at raised risk. They are daily tablets that cut the small amount of oestrogen the body still makes once periods stop. They only help against oestrogen-driven cancers, and they do not replace screening. This page explains who they suit, how they compare with tamoxifen, and what to expect. At CION Cancer Clinics, our team helps carriers and their families plan checks, next steps and support after a genetic result.
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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
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On this page
- Can an aromatase inhibitor lower my breast cancer risk?
- Who might be offered it, and who should not take it
- What happens when you start an aromatase inhibitor?
- The words you will meet, in plain language
- Aromatase inhibitors compared with tamoxifen
- What this page cannot tell you
- Four things women tell us, and what is actually true
- Common questions about aromatase inhibitors for prevention
The short answer
Can an aromatase inhibitor lower my breast cancer risk?
For some women, yes. Aromatase inhibitors are daily tablets that lower the amount of oestrogen in the body after menopause. In large trials of women at raised risk, they reduced the number of breast cancers that developed. They are an option only after menopause, and only for the kind of breast cancer that feeds on oestrogen.
How a tablet can prevent a cancer
Most breast cancers grow in response to oestrogen. After menopause the ovaries stop making it, but the body still makes a smaller amount in fat and other tissue using an enzyme called aromatase. These tablets block that enzyme. With less oestrogen around, early abnormal cells that depend on it are less likely to grow into a cancer.
Why this matters for families with a gene fault
The trials recruited women with a strong family history or other risk factors, not only women with a known gene fault. That means the evidence in carriers specifically is thin. It fits best where the cancers in the family tend to be oestrogen-driven, which is more common with some genes than others.
An aromatase inhibitor lowers risk. It does not remove it, and it does not replace breast screening.Who it suits
Who might be offered it, and who should not take it
The decision turns on three things: menopause, the type of breast cancer your gene tends to cause, and your bones.
Women after menopause at raised risk
This is the group the trials studied. UK national guidance makes an aromatase inhibitor the first choice for women past menopause at high family risk, and suggests considering it at moderate risk, unless their bones are already badly thinned.
Carriers of BRCA2, PALB2, CHEK2 or ATM
Breast cancers linked to these genes are more often oestrogen-driven. In principle that makes a hormone-blocking tablet a better fit, though direct trial evidence in carriers is limited.
BRCA1 carriers
Breast cancers linked to BRCA1 are more often not oestrogen-driven. A tablet that lowers oestrogen may help less. This is a question to weigh carefully with your oncologist rather than assume either way.
Who should not take it
These are the situations where it is usually ruled out.
- Women who have not reached menopause
- Women with severe bone thinning
- Women whose risk is close to average
Not sure whether this applies to you?
Ask an oncologistIf you decide to go ahead
What happens when you start an aromatase inhibitor?
A risk estimate first
Your oncologist or counsellor works out how high your breast cancer risk is from your gene result and family history. The benefit is only worth the side effects when the risk is clearly raised.
Confirming menopause
If there is any doubt, such as after a hysterectomy, a blood test can check whether the ovaries have stopped working. The tablets do not work on their own while the ovaries still make oestrogen.
A bone density scan
These tablets can thin the bones. A scan before you start gives a baseline. Calcium, vitamin D and weight-bearing exercise are usually advised alongside.
One tablet a day, with regular reviews
The usual course in the trials was five years. You are reviewed for side effects, bone health and breast screening throughout. Screening carries on exactly as before.
On your prescription
The words you will meet, in plain language
- Aromatase inhibitor
- A tablet that blocks the enzyme the body uses to make oestrogen after menopause. Anastrozole and exemestane are the two used for prevention.
- Chemoprevention
- Taking a medicine to lower the chance of a cancer developing in someone who does not have one. It is not chemotherapy.
- Oestrogen receptor positive
- A breast cancer whose cells use oestrogen to grow. Hormone-blocking tablets can only prevent this kind.
- Postmenopausal
- After periods have stopped for good because the ovaries no longer make eggs or much oestrogen, whether naturally or after surgery.
- Bone density scan
- A quick, low-dose X-ray of the hip and spine that measures how strong the bones are. Doctors may call it a DEXA scan.
- Relative risk reduction
- How much a medicine lowers risk compared with not taking it. The real benefit to you depends on how high your risk was to begin with.
Side by side
Aromatase inhibitors compared with tamoxifen
Aromatase inhibitor
Tamoxifen
Only after menopause
Before or after menopause
No raised risk of womb cancer or blood clots
Small raised risk of womb cancer and blood clots
Can thin the bones, so bones are checked
Tends to protect bone after menopause
Joint aches and stiffness are common
Hot flushes are common
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Being straight with you
What this page cannot tell you
It cannot tell you how much an aromatase inhibitor would lower your own risk. That depends on your gene, your age, your family history and the type of breast cancer seen in your relatives. The trials were not large enough in carriers to give a gene-by-gene answer, and the evidence is still growing.
It cannot weigh the trade-off for you
The trials have shown fewer breast cancers. They have not yet shown fewer deaths, partly because that takes many more years to measure. Whether the benefit is worth the side effects is a personal judgement, made with an oncologist who knows your history. What your specific variant means is a question for the counsellor who ordered the test.
Who this does not apply to
Most women with a family history do not need a preventive medicine at all. If your risk is only slightly raised, or you have not reached menopause, this tablet is not for you. Screening, and in some cases tamoxifen, may be discussed instead.
If you already take an aromatase inhibitor as treatment for breast cancer, this page is not about you. Follow your treating oncologist's plan.Commonly believed
Four things women tell us, and what is actually true
"If I take the tablet, I will not get breast cancer."
It lowers the chance. It does not remove it. Some women who take it still develop breast cancer, which is why screening must carry on exactly as planned.
"It is chemotherapy, so my hair will fall out."
It is a hormone tablet, not chemotherapy. It does not cause the hair loss, sickness or low blood counts people link with chemotherapy. Its side effects are mostly joint aches, hot flushes and bone thinning.
"It will lower my ovarian cancer risk too."
There is no evidence it lowers ovarian cancer risk. For carriers of genes that raise ovarian risk, that question is handled separately, usually by discussing removal of the ovaries and tubes.
"If the joint pain starts, I have to put up with it."
You do not. Tell your doctor. Exercise and simple pain relief often help, switching to the other aromatase inhibitor sometimes helps, and stopping is always your choice.
Questions we are asked
Common questions about aromatase inhibitors for prevention
Can I take an aromatase inhibitor before menopause?
Not on its own. Before menopause the ovaries make most of the body's oestrogen, and these tablets cannot block that. Tamoxifen is the medicine usually discussed for women who are still having periods. Your oncologist will explain which fits your situation.
How long would I take it for?
The prevention trials used a course of five years. In long follow-up of those trials, the lower rate of breast cancer appeared to continue after the tablets stopped. Your doctor will review the plan with you each year rather than set it and forget it.
What are the most common side effects?
Joint aches and stiffness, hot flushes, vaginal dryness and tiredness are the ones women mention most. Bone thinning is the one doctors watch most closely, because it causes no symptoms until a bone breaks. Most side effects ease once the tablet is stopped.
Is it safe to take for a long time?
For most women after menopause it is well studied over a course of years. The main long-term concern is bone strength, which is why bone scans and calcium and vitamin D are part of the plan. Report any new bone or joint pain rather than waiting.
Is it approved for prevention in India?
Aromatase inhibitors are widely available in India as treatment for breast cancer, and generic versions are made here. Using them for prevention is a decision your oncologist makes on the evidence and on guidance from bodies such as NICE, and it is discussed with you before any prescription.
Does it replace my breast MRI or mammogram?
No. Screening continues exactly as planned for your gene. The tablet lowers the chance of a cancer. Screening finds one early if it develops anyway. The two do different jobs and you need both.
What if I already had my ovaries removed?
Removing the ovaries brings on menopause, so an aromatase inhibitor becomes possible. Whether it adds enough benefit on top of the surgery depends on your gene and your breast risk. Ask your oncologist to weigh it, especially if you are taking HRT.
Can I stop if the side effects are too much?
Yes. This is prevention, not treatment for an existing cancer, and stopping is always your choice. Talk to your doctor first, because switching to a different tablet or managing the side effect sometimes lets you carry on comfortably.
Your Specialists
Meet CION's oncologists. Bring your family history or genetic report to them.
Our medical oncologists see people with a strong family history of cancer, arrange genetic counselling and testing where it fits, and plan the checks that follow.
Medical Oncologist
Dr. C. Raghavendra Reddy
MBBS(Gold Medal), DNB(General Medicine), DM(Medical Oncology)(Gold Medal)
Medical Oncologist
Dr. Bharati Devi Gorantla
MBBS, MD(General Medicine), DM(Medical Oncology)(Adyar,Chennai), ECMO, MRCP SCE(UK)
Medical Oncologist
Dr. Owais Mohammed
MBBS, MD (General Medicine), DrNB (Medical Oncology), ECMO, MRCP SCE (Medical Oncology) (UK)
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Sources
- National Cancer Institute — Breast Cancer Prevention (PDQ) - Patient Version
- NICE — Familial breast cancer: classification, care and managing breast cancer and related risks in people with a family history of breast cancer (CG164)
- US Preventive Services Task Force — Breast Cancer: Medication Use to Reduce Risk
- National Cancer Institute — BRCA Gene Changes: Cancer Risk and Genetic Testing Fact Sheet
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.
Keep reading
Related pages
Tamoxifen and raloxifene for risk reductionThe options for women before menopauseSide effects of preventive hormone medicationWhat the tablets feel like to live withChemoprevention explainedHow preventive medicines work across genesSurgery, medication or surveillanceHow to weigh a tablet against the other routes
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