Endocrine (Hormonal) Therapy
Decoding Endocrine (Hormonal) Therapy for Breast Cancer
If you’ve been told your breast cancer is hormone-receptor positive, you’re not alone. About two-thirds of breast cancers fall into this category—meaning the cancer cells grow in response to estrogen and/or progesterone. Endocrine therapy works by blocking or lowering these hormones, which helps stop cancer from growing or coming back.
For any stage of breast cancer, endocrine therapy may play a key role in your treatment plan. It’s often taken by pill or injection, and in some cases, paired with other targeted therapies to increase effectiveness.
Types of Endocrine Therapy Medications
Endocrine therapy isn’t one-size-fits-all. Your doctor will choose the option that best fits your diagnosis, age, and life plans.
Aromatase Inhibitors
- What they do: Decrease estrogen production in your body
- Examples: anastrozole (Arimidex®), letrozole (Femara®), exemestane (Aromasin®)
- How you take it: Daily pill
- Best for: People who are postmenopausal (naturally or surgically) or pre-menopausal and receiving ovarian suppression medications
Selective Estrogen Receptor Modulators (SERMs)
- What they do: Block estrogen’s action on breast cells
- Example: Tamoxifen (Nolvadex®)
- How you take it: Daily pill
- Best for: Premenopausal and postmenopausal patients
Selective Estrogen Receptor Downregulators (SERDs)
- What they do: Block and break down estrogen receptors
- Examples: fulvestrant (Faslodex®), elacestrant (Orserdu®)
- How you take it:
- Fulvestrant: Monthly injection
- Elacestrant: Daily pill
- Best for: People who are postmenopausal (naturally or surgically) or pre-menopausal and receiving ovarian suppression medications
Ovarian Function Suppression (OFS)
- What it does: Temporarily shuts down the ovaries to reduce hormone production
- Examples: goserelin (Zoladex®), leuprolide (Lupron Depot®)
- How you take it: Injection every 4 to 12 weeks
- Note: OFS is always combined with either tamoxifen or an aromatase inhibitor
- Best for: people who are premenopausal or perimenopausal
If You’re Premenopausal
If you haven’t gone through menopause, your body is still producing estrogen and progesterone. For certain types of breast cancer, your care team may suggest endocrine therapy to help limit how estrogen fuels cancer cells.
Considerations For DCIS
Considerations for Early Invasive Breast Cancer Stage I-III, including IBC
Considerations for MBC
Endocrine Therapy After Menopause
After menopause, your body naturally produces much less estrogen and progesterone because your ovaries slow down hormone production. But your body doesn’t stop making estrogen altogether—fat cells continue to make small amounts.
To block estrogen where it matters most—in breast cancer cells—your care team may recommend aromatase inhibitors, which stop estrogen from forming. These medications only work in people whose ovaries are no longer active, so they’re typically prescribed to those who are postmenopausal (naturally or surgically) or for those who are premenopausal and receiving ovarian function suppression medications. Tamoxifen is also an effective treatment for postmenopausal patients.
Considerations for DCIS
Considerations for Early Invasive Breast Cancer Stage I-III, Including IBC
Considerations for MBC
Common Side Effects from Tamoxifen:
- Hot flashes and night sweats
- Vaginal discharge
- Fatigue
- Mood swings
- Weight gain
- Leg cramps
- Rare: blood clots and uterine cancer.
Common Side Effects from Aromatase Inhibitors:
- Joint pain or stiffness
- Hot flashes and night sweats
- Vaginal dryness
- Fatigue
- Mood swings
- Hair thinning
- Weight gain
- Loss of bone density (osteopenia or osteoporosis)
To explore suggestions on managing side effects and symptoms, visit the Symptom Management Library.
Questions to Ask Your Care Team About Endocrine Therapy
It’s okay to not have all the answers yet. Endocrine therapy can be complex, but the more you understand, the more equipped you’ll be to make choices that feel right for you. Use this checklist to feel more prepared heading into appointments.
Treatment Plan Basics
Do I need endocrine therapy?
What makes this treatment the right choice for my diagnosis?
What type of endocrine therapy will I be receiving?
Timing and Duration
When will I start endocrine therapy?
How long will I need to stay on it?
Side Effects and Support
What side effects should I expect from this treatment?
How long do these side effects usually last?
Are there certain symptoms I should tell you about right away?
What can I do to ease or manage side effects during treatment?
Cost and Medication Options
Is there a generic version of this medication available?
