Tamoxifen for Breast Cancer

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Tamoxifen (tamoxifen citrate) is a prescription medication approved by the U.S. Food and Drug Administration (FDA) to treat certain adults with breast cancer.

What Members Say

MHT logo These insights are based on 14,312 comments about Tamoxifen from MyBCTeam members. These are the experiences of a small number of people and are not meant to be medical advice.

Benefits:

Often serves as an added layer of protection for hormone receptor-positive breast cancer.
Once or twice daily oral dosing can fit easily into a daily routine.
May remain an option when bone loss makes aromatase inhibitors harder to use.

Considerations:

Joint pain, muscle cramps, and stiffness can affect walking, work, and daily activities.
Vaginal bleeding, uterine thickening, polyps, and pelvic symptoms need prompt medical attention.
Blood clots, stroke, and uterine cancer are serious labeled risks.

How Tamoxifen Works and How It’s Taken

Tamoxifen is an estrogen agonist and antagonist. This means it may block estrogen in some parts of the body and act like estrogen in others.

In breast tissue, Tamoxifen competes with estrogen for places called estrogen receptors. This may reduce signals that help some breast cancer cells grow.

Doctors prescribe Tamoxifen:

To treat metastatic breast cancer in women and men — Metastatic means the cancer has spread to other parts of the body.
To treat breast cancer in women after surgery and other early treatment — This includes women with cancer in nearby lymph nodes and women without cancer in nearby lymph nodes.
To reduce the chance of cancer developing in the other breast during adjuvant treatment — Adjuvant treatment is treatment given after the first breast cancer treatment.
To reduce the risk of invasive breast cancer in women with ductal carcinoma in situ (DCIS) after breast surgery and radiation
To reduce the chance of breast cancer in women age 35 or older who are at high risk — The benefits and risks should be reviewed for each woman.

In premenopausal women with metastatic breast cancer, Tamoxifen may be used instead of surgery or radiation to stop the ovaries from working. People whose tumors are estrogen receptor-positive may be more likely to benefit.

Tamoxifen citrate tablets are taken by mouth. Your healthcare provider will tell you how much to take, when to take it, and how long to continue treatment.

Typical Dosing for Breast Cancer

For breast cancer, the recommended dose is 20 to 40 milligrams each day. A dose above 20 milligrams per day should be divided into a morning dose and an evening dose.

For adjuvant breast cancer treatment, current clinical trial data support treatment for about five years.

For DCIS, the recommended dose is 20 milligrams once daily for five years.

For women at high risk of breast cancer, the recommended dose is 20 milligrams once daily for five years.

Doctors may pause treatment, lower the dose, or stop treatment if side effects are serious or too hard to manage.

This information is based on prescribing information, but your healthcare provider may tailor your treatment plan. Always follow their guidance.

Top Advice From Members on Tamoxifen

These insights are based on 14,312 comments about Tamoxifen from MyBCTeam members.

Members who use Tamoxifen often say it helps to stay in close contact with your care team, especially when side effects or bleeding show up. Many also recommend tracking how you feel over time, asking questions about benefits and risks, and trying simple routines that make day-to-day side effects easier to manage.

1
Tell your doctor about any vaginal bleeding or pelvic symptoms.
“I was cautioned to contact them immediately if I had any vaginal bleeding due to being on Tamoxifen. Tamoxifen can lead to uterine cancer. If you have bleeding, they will often do a biopsy.”
2
Be careful about pregnancy and birth control while taking Tamoxifen.
“Tamoxifen does not stop you from ovulating or put you into menopause. I would seriously recommend that you use a very reliable form of birth control.”
3
Try simple strategies to manage hot flashes and night sweats.
“I always have a fan, ice water, and something to dry off with. My cooling gel pillow helps at night.”

Connect with others who understand life with breast cancer. Join MyBCTeam for free.

Tamoxifen Side Effects

In clinical trials of Tamoxifen for breast cancer, side effects differed depending on how Tamoxifen was used.

For adjuvant breast cancer, the most common side effects include:

Hot flashes
Vaginal discharge
Irregular menstrual periods

For metastatic breast cancer, the most common side effects include:

Hot flashes

Serious Side Effects and Warnings

Tamoxifen can cause serious side effects that may require immediate medical attention. These include:

Uterine malignancies — These malignancies can include endometrial cancer and uterine sarcoma.
Stroke — Strokes can occur.
Thromboembolic events — Blood clots can occur, including deep vein thrombosis and pulmonary embolism.
Changes in the uterus that are not cancer — These changes can include endometrial thickening and polyps.
High calcium levels in the blood — Hypercalcemia can occur in some people with metastatic breast cancer that has spread to the bones.
Liver problems — These problems can include changes in liver enzymes, fatty liver, cholestasis, hepatitis, liver tissue damage, and rare liver cancer.
Hematologic effects — Low blood cell counts, including low platelets, low white blood cells, neutropenia, anemia, and pancytopenia, can occur.
Eye problems — These problems can include cataracts, changes in the cornea, changes in color vision, retinal vein thrombosis, and retinopathy.
Embryo-fetal toxicity — Harm to the child can occur if taken during pregnancy.

Get medical help right away if you think you are having a serious reaction.

How To Save on Tamoxifen

Generic tamoxifen does not have a manufacturer-sponsored copay card or savings card, but you can lower its cost using free third-party discount cards or pharmacy coupons.

What To Know Before Taking Tamoxifen

Before starting Tamoxifen, your doctor will perform:

A breast exam
A mammogram
A gynecologic exam
Pregnancy test if you can become pregnant

Do not take Tamoxifen if you have had an allergic reaction to Tamoxifen or any of its ingredients.

If you are taking Tamoxifen to lower your risk of breast cancer or because you have DCIS, do not take it if:

You need to take a coumarin-type blood thinner, such as warfarin
You have had a deep vein thrombosis (DVT)
You have had a pulmonary embolism, or blood clot in the lungs

Tamoxifen is used to lower breast cancer risk only in women who meet the high-risk criteria in the prescribing information. Your healthcare provider will review your personal risks and possible benefits.

Tell your doctor about all medicines you take, including prescription drugs, over-the-counter medicines, vitamins, and herbal supplements.

If you miss a dose, take it when you remember. Then take your next dose at the usual time. If it is almost time for your next dose, skip the missed dose. Do not take extra tablets.

Tamoxifen can harm your baby if you are pregnant. Do not become pregnant while taking Tamoxifen or for two months after stopping it. Use a barrier method or another nonhormonal form of birth control during this time. If you become pregnant, contact your healthcare provider right away.

Do not breastfeed while taking Tamoxifen because of the risk of serious side effects in a nursing baby.

Community FAQs

These answers are fact-checked by our editorial staff.

How effective is Tamoxifen for breast cancer?

A large review included 36,689 women with early breast cancer. Among women whose cancer was estrogen receptor-positive or had unknown receptor status, had spread to nearby lymph nodes, and who took Tamoxifen for about five years, 61.4 percent were alive at 10 years. This compared with 50.5 percent in the control group.

In the same group, 59.7 percent had no return of breast cancer at 10 years, compared with 44.5 percent in the control group.

In women with DCIS who had breast surgery and radiation, Tamoxifen reduced the risk of invasive breast cancer by 43 percent.

Can Tamoxifen cause uterine bleeding or uterine cancer in people taking it for breast cancer?

Tamoxifen is linked to a higher risk of cancers of the uterus. These include cancer of the uterine lining, called endometrial cancer, and rare cancers called uterine sarcomas.

Tamoxifen is also linked to noncancerous changes in the uterus, such as thickening of the uterine lining and polyps.

People taking Tamoxifen, or who took it in the past, should contact their healthcare provider right away if they have:

Vaginal bleeding or bloody discharge
Changes in menstrual bleeding
Changes in vaginal discharge
Pelvic pain or pressure

In one study of high-risk women who still had their uterus, about 1 in 1,000 women taking placebo developed endometrial cancer each year. About 2 in 1,000 women taking Tamoxifen developed endometrial cancer each year. Fewer than 1 in 1,000 women taking Tamoxifen developed uterine sarcoma each year.

These numbers do not show the exact risk for every person. The risk is different for people who no longer have a uterus.

Can Tamoxifen be used in men for breast cancer?

Yes. Tamoxifen is used to treat metastatic breast cancer in men. Metastatic means the cancer has spread to other parts of the body.

Tamoxifen blocks some effects of estrogen in breast tissue. This may help slow the growth of breast cancer.

The prescribing information states that Tamoxifen is effective for the palliative treatment of male breast cancer. Palliative treatment means treatment that helps control the cancer and its symptoms.