Sticking With Endocrine Therapy for the Long Haul: What It’s Like and Why It Matters

Written by Hallie Levine
Medically Reviewed by Zilpah Sheikh, MD on September 18, 2025
8 min read

Amy Ridings, 38, was diagnosed with stage II hormone receptor-positive, HER2-negative breast cancer in 2023. She was shocked when her doctors said having a double mastectomy, chemotherapy, and other treatments would still leave a 15% chance of her cancer returning. 

“I wanted to do everything in my power to attack my cancer at all angles,” says Ridings, who lives in Dallas, Texas. Her doctor recommended endocrine therapy,  a type of medication that's usually always part of standard treatment for hormone receptor-positive breast cancer. 

Endocrine therapy has been shown to cut the risk of recurrence in women with hormone receptor-positive early-stage breast cancer by about 50%.

Ridings decided to take exemestane (Aromasin). It’s an aromatase inhibitor, a drug that lowers estrogen in your body to help slow the growth of any hormone-sensitive breast cancer. She’s also on Lupron, a prescription hormone therapy that suppresses estrogen and has put her in temporary menopause, so that she can take exemestane. She plans to be on both drugs for 5-10 years.

“I don’t love the idea of being on these medications for so long, but I need to do everything I can to reduce the chance of cancer recurrence and improve my odds of survival,” she says.

About two-thirds of all breast cancers are hormone receptor-positive breast cancers. This means they grow in response to hormones such as estrogen and progesterone. Your breast cancer cells have receptors that attach to these hormones, which helps them grow, says Rachel Layman, MD, a breast medical oncologist at the University of Texas MD Anderson Cancer Center in Houston, Texas. 

Endocrine therapy prevents this from happening.

“It’s sometimes known as hormone therapy, which is confusing because we’re not giving patients hormones, but rather manipulating the hormones they do have. It’s really a form of antiestrogen therapy,” Layman says.

“Almost every breast cancer patient with this type of breast cancer is offered it because it’s been shown to help at all stages of disease, including what we call stage 0, or ductal carcinoma in situ,” says Layman. It doesn’t help women whose tumors don’t have hormone receptors (also known as hormone receptor-negative breast cancer).

You usually start hormone therapy right after breast cancer surgery, notes Layman. And it’s taken for 5-10 years. “We offer treatment longer than five years to women who are at higher risk of recurrence,” explains Layman. A test called the Breast Cancer Index can help you and your doctor figure out if you will benefit from more than five years of hormone therapy. 

There are several different types of drugs used as endocrine therapy. They fall into two main groups.

Drugs that block estrogen receptors

There are two types:

Selective estrogen receptor modulators (SERMs). They include tamoxifen, which can be used by all women, and toremifene (Fareston), which can only be used in postmenopausal women with metastatic breast cancer. 

Selective estrogen receptor degraders (SERDs). These are usually used in postmenopausal women. They include elacestrant (Orsedu) and fulvestrant (Faslodex), which can be used only by women with a certain gene mutation.

Drugs that lower estrogen levels

These are called aromatase inhibitors (AIs). They stop estrogen production in your body. They can be used when you've already gone through menopause, although premenopausal women can use them if they take a drug to suppress ovulation, like Lupron. 

They include:

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

Often, doctors suggest tamoxifen for premenopausal women and aromatase inhibitors for postmenopausal ones, says Layman. But their recommendations can differ, based on other things like your cancer’s genetic makeup, your age, and other chronic health conditions you have.

Endocrine therapy may have side effects, some of which can affect your quality of life. “They vary from patient to patient — some crop up within days, while others don’t show up for months,” says Layman. Here are some that you may experience.

Day-to-day side effects

When Ridings started endocrine therapy, she experienced intense hot flashes that made it almost impossible to concentrate or sleep. “It was like I had been thrust full speed into menopause,” she says. Other side effects you may notice include:

  • Vaginal dryness
  • Headache
  • Nausea
  • Fatigue
  • Loss of appetite
  • Muscle, joint, or bone pain
  • Pain at the injection site

While symptoms are often worse in premenopausal women, they can happen in postmenopausal women, too. “We’re lowering estrogen levels even more than what occurs naturally in menopause,” explains Layman.

Long-term side effects

Endocrine therapy can lead to bone loss over time due to low estrogen levels. Susan Cassidy, 67, already had osteoporosis when she began endocrine therapy for her hormone receptor-positive, HER2-negative breast cancer. It continued to advance during her treatment, even though she was on zoledronic acid (Zometa), a drug that helps slow down bone loss. 

“Every year the side effects got worse and worse,” Cassidy, who lives in Fairfield, Connecticut, recalls. “I felt like I was 90 years old. Every joint in my body hurt.”

Most of the time, doctors can check bone loss from endocrine therapy through bone density testing, says Layman. “We typically get a baseline bone density test at the start of treatment, and if it’s normal, repeat it every two years,” she explains. If your scan does show low bone density (osteopenia), Layman recommends that you get checked annually. “Oftentimes, we refer patients to an endocrinologist, who can discuss with them whether they want to start medication to decrease bone loss, or if they just want to keep a close eye on it,” she says.

Cassidy stayed on endocrine therapy for five years. After that, she took the Breast Cancer Index test to figure out her risk of recurrence. “It was quite low —about 3% — and my doctor and I both decided continuing might trash my bones,” she says. She decided to stop therapy, rather than go on for another five years.

About a third of patients with on endocrine therapy stop taking it early due to side effects, which raises the risk of recurrence and death. “Always let your doctor know if you see any side effects, as there’s a lot we can do to help manage them so you can stay on the medication,” stresses Layman. Here are some things to try for managing common side effects:

Hot flashes. Your doctor can prescribe a medication such as fezolinetant (Veozah), which works in your hypothalamus — the part of your brain that controls body temperature. A type of antidepressant medication called selective serotonin reuptake inhibitors (SSRIs) may also help. Ridings found relief when her doctor prescribed oxybutynin, a drug normally used to treat an overactive bladder that also helps with hot flashes. “After a week, they went away completely, and haven’t returned,” she says. 

Muscle and joint aches. Physical activity is one of the best ways to treat aches and stiffness from endocrine therapy, says Layman. Becky Webber, 39, was diagnosed with stage II triple-positive breast cancer in 2021. She says yoga has offered a lot of relief from muscle aches and pains. “I’m a big fan of yin yoga, where you hold poses for a few minutes at a time,” explains Webber, who lives in Denver, Colorado. She also swears by tart cherry juice, which some research suggests can help relieve muscle soreness and inflammation.

Vaginal dryness. Your doctor may recommend over-the-counter lubrication products. You can also ask them about a prescription vaginal estrogen cream. “Since it’s only absorbed locally, in your vagina, it’s considered safe to use in women with hormone-positive breast cancer,” explains Layman.

Social support is very important when you are on endocrine therapy. Research suggests that it may make it easier for you to stick with this treatment long term. You can find support in places such as:

Your doctor's office. They should listen to your concerns about side effects and offer suggestions to help you, says Layman. If side effects affect you mentally, they can connect you to a therapist.

Online support groups. This can be on social media sites such as Facebook or through organizations such as the National Breast Cancer Foundation, the American Cancer Society, and the Susan G Komen Foundation.

Your place of worship.

Other breast cancer survivors. Sometimes, it helps to talk to other women who have been there, says Ridings. They can offer tips on what they’ve done to make endocrine treatment more bearable.

Insurance usually covers the cost of endocrine therapy for breast cancer, as it’s medically necessary, says Layman. It also often covers the cost of the Breast Cancer Index, so you can see whether you need to be on the medication for 5-10 years. 

You may still have a copay with endocrine therapy. In general, women with breast cancer spend around $203 a year on out-of-pocket drug costs, according to a 2023 review published in JAMA Network Open.

If you have hormone receptor-positive breast cancer, you should talk to your doctor about endocrine therapy. For most women, the benefits far outweigh the risks, stresses Layman. While there are side effects, most are manageable.