Up to 60 percent of people with breast cancer take a break from hormone therapy or stop their treatment early. For individuals taking tamoxifen (sold as Soltamox), the impact of side effects or other life events may influence their decision to take a hiatus from the medication.

“Has anyone taken a break from tamoxifen (and the decision was supported by your oncologist)?” one MyBCTeam member asked. “Thoughts on doing so?”

Continue reading to learn more about taking a break from tamoxifen.

What Is Tamoxifen?

Tamoxifen is a breast cancer treatment used to prevent cancer from recurring (returning), also known as adjuvant therapy. Many people take this hormonal therapy for five to 10 years to treat or prevent certain types of breast cancer. It can decrease the risk of breast cancer recurring or new breast cancer developing by 30 percent to 50 percent.

Tamoxifen works by blocking the effect of estrogen on hormone receptor-positive breast cancer. In this type of cancer, estrogen can encourage breast cancer cells to grow and divide. By blocking its effect, tamoxifen can slow or stop cancer cell growth.

You may take tamoxifen if:

• You have a high risk of breast cancer but haven’t been diagnosed yet.
• You’ve had breast-conserving surgery for hormone receptor-positive ductal carcinoma in situ.
• You have hormone receptor-positive invasive breast cancer that’s been treated with surgery.
• You have hormone receptor-positive breast cancer that’s spread to other parts of your body.

Tamoxifen can be taken whether or not you have gone through menopause.

Why Do People Take a Break From Tamoxifen?

One survey of 32 women found that those who stopped taking their hormone therapy usually did so one to two years after it was prescribed. People might decide to temporarily or even permanently stop using tamoxifen for many reasons.

Side Effects

Tamoxifen can have side effects that affect your day-to-day life. Some common side effects that you may find difficult to manage include:

• Hot flashes
• Weight gain
• Vaginal discharge and dryness
• Joint pain
• Fatigue
• Mood swings

Some people may stop taking tamoxifen to regain a sense of normalcy. One MyBCTeam member said, “I am currently on a one-month break and feeling much better! The weight gain was too overwhelming for me. I felt miserable all the time. I am just now realizing the bone/joint pain was stemming from the tamoxifen.”

If you stop tamoxifen to get a break from side effects, you should be aware that they may not fade right away. In fact, fatigue can linger for weeks or months after you stop tamoxifen.

The side effects of tamoxifen may actually be a sign that the medication is working. Several studies have found that people who experience hot flashes and joint pain are less likely to have breast cancer recurrence. However, if you don’t have side effects, it doesn’t mean the drug isn’t working.

If you experience side effects while taking tamoxifen, it’s important to talk to your cancer care team about ways to manage them. Never stop taking your medication without talking to your doctor first. Your doctor may suggest ways to manage your side effects.

Serious Medical Issues

Some people stop taking tamoxifen if they have a serious or life-threatening side effect. Tamoxifen can increase your risk of uterine cancer, blood clots, and stroke. You should talk to your doctor right away if you experience any of the following symptoms:

• Unusual vaginal bleeding
• Changes in vaginal discharge
• Chest pain
• Shortness of breath
• Sudden swelling in one or both legs
• Confusion
• Vision problems
• Sudden, severe headache

You may also need to temporarily stop tamoxifen if your tumor gets bigger for a short time — also known as a tumor flare — when you first start treatment. A tumor flare can occur after beginning tamoxifen in some people whose cancer has spread to the bones, which can cause bone pain and a dangerously high level of calcium in your blood. If this happens, you may need to take a break from tamoxifen.

Pregnancy

Tamoxifen is usually the first choice of hormonal therapy for premenopausal individuals with hormone receptor-positive breast cancer, including those who may wish to have children. However, tamoxifen is harmful to an unborn baby if taken during pregnancy. Individuals with breast cancer taking tamoxifen may take a break to get pregnant.

A 2023 study in The New England Journal of Medicine found that some younger people could safely take a break from hormonal therapy to have a baby. The study included women younger than 42 years who were previously diagnosed with early-stage breast cancer, had been taking hormonal therapy for one-and-a-half to two-and-a-half years, and wished to become pregnant. Researchers found that the short-term risk of breast cancer recurrence didn’t increase during the pause to have a baby. However, more studies are needed to learn if the break in therapy will affect long-term risk.

Financial Stress

Prescriptions can be expensive. If you have a financial hardship or lose insurance coverage, it may be hard for you to pay for tamoxifen. Talk with your doctor or pharmacist about resources that may be available to help you pay for your medication.

What Can You Expect After Taking a Break From Tamoxifen?

If you stop taking tamoxifen, you may have an increased risk of breast cancer recurrence. Taking tamoxifen for the prescribed length of time can lower your risk of recurrence by up to 50 percent and decrease your risk of dying from breast cancer by 30 percent, according to Breastcancer.org.

Although stopping tamoxifen may improve your side effects, talk to your doctor before you stop taking it. Your oncologist may be able to suggest ways to improve your side effects, and you can make a shared decision about your treatment plan.

Restarting Hormonal Therapy

If you take a break from tamoxifen, your doctor can help you weigh the potential benefits and risks of restarting hormonal therapy. In most cases, you can still lower your risk of breast cancer recurrence if you restart your treatment with tamoxifen or another hormonal therapy.

If you can’t take tamoxifen, you may be able to take a different type of hormonal therapy called an aromatase inhibitor. Instead of blocking the effect of estrogen, as tamoxifen does, these drugs stop your body from making estrogen.

Examples of aromatase inhibitors include:

• Letrozole (Femara)
• Anastrozole (Arimidex)
• Exemestane (Aromasin)

Aromatase inhibitors and tamoxifen can also cause some similar side effects, such as hot flashes, but also some different ones. Aromatase inhibitors don’t increase your risk of uterine cancer and very rarely cause blood clots. However, they do commonly cause muscle and joint pain.

Remember that it’s never a good idea to stop taking any medication without speaking to your care team first. They can help you evaluate your options and find alternatives in many cases.

Talk With Others Who Understand

MyBCTeam is the social network for people with breast cancer and their loved ones. On MyBCTeam, more than 64,000 members come together to ask questions, give advice, and share their stories with others who understand life with breast cancer.

Have you taken a break from tamoxifen? Did you restart tamoxifen or another hormonal therapy? Share your experiences in the comments below, or start a conversation by posting on your Activities page.