Understanding Fulvestrant Therapy for Advanced Breast Cancer

Fulvestrant (brand name Faslodex) is a hormone therapy used to treat advanced stages of a certain type of breast cancer in postmenopausal women. Specifically, it is used in estrogen receptor (ER) positive breast cancers that have spread to other parts of the body and no longer respond to other anti-estrogen therapies.

What is fulvestrant and how does it work?

Fulvestrant is an estrogen blocking drug. It works by binding to estrogen receptors in breast cancer cells and blocking estrogen’s actions. Many breast cancer cells have estrogen receptors and depend on the hormone estrogen to grow. By interfering with the receptors and denying breast cancer cells access to estrogen, fulvestrant can slow or stop cancer growth.

Fulvestrant is what’s called a selective estrogen receptor downregulator (SERD). Unlike other hormone therapies like tamoxifen that just block estrogen receptors, fulvestrant also causes the cell to get rid of the estrogen receptor once it binds to it. This makes the cancer cell permanently less sensitive to estrogen’s effects.

When is fulvestrant used?

Fulvestrant is approved to treat postmenopausal women with advanced, metastatic, or recurrent ER-positive breast cancer in the following situations:

  • When the cancer worsens despite anti-estrogen therapy with drugs like letrozole or tamoxifen
  • When the cancer relapses within one year of completing adjuvant anti-estrogen therapy
  • When the cancer progresses after previous hormone therapy for advanced disease

Fulvestrant may be used alone or combined with other treatments that suppress estrogen production. Using multiple therapies can be more effective for some women.

How is fulvestrant given?

Fulvestrant is given by intramuscular injection, meaning it is injected into the muscle. It cannot be taken as a pill because it would be broken down before reaching cancer cells.

Most patients receive an injection into each buttock. The injections are given on:

  • Day 1
  • Day 15
  • Day 29

After the first three loading doses, injections are continued once a month for as long as the cancer responds and side effects are tolerable.

The injections contain thick medication that has to go into the muscle slowly, so the process takes about 2-3 minutes per injection. Many patients report feeling some burning or pressure during the injection. Using a warm or cold pack for 10-15 minutes right before can make it more comfortable.

What are possible side effects?

As with any medication, fulvestrant can cause unwanted side effects along with the desired effects on cancer cells. It has been studied in clinical trials with over 700 women. Most side effects are mild and manageable. Common issues include:

  • Injection site reactions – Pain, inflammation, bleeding, or irritation near the injection area occurs in up to 20% of patients. Using warm/cold compresses can alleviate discomfort.
  • Hot flashes – Sudden sensations of body heat are common due to lowered estrogen levels. Layering clothing, staying hydrated, and avoiding triggers can help reduce hot flash frequency and severity.
  • Joint pain – Stiffness or achiness, especially in the hands, feet, knees, hips or back, occurs in about 20% of patients on fulvestrant. Over-the-counter pain medication provides relief for most women.

Less common side effects, affecting around 10% or fewer patients, include headaches, nausea, vomiting, tiredness, leg swelling, vaginal bleeding or discharge, loss of appetite, diarrhea and constipation.

Rare but serious risks include a higher chance of blood clots forming in the veins (deep vein thrombosis) as well as liver problems. Patients should monitor for leg swelling/pain, abdominal pain, yellowing skin/eyes, or easy bruising/bleeding and report these immediately. Monthly bloodwork helps detect any liver changes early on.

What kind of monitoring is involved?

Patients on fulvestrant will have regular check-ins, exams and bloodwork to monitor cancer progression and side effects. Typically visits are every month. Bloodwork helps detect any changes in liver function, electrolytes or blood cell counts caused by the medication.

Reporting any side effects when they start allows for early intervention. Pain, swelling or other issues at the injection site should be reported before the next dose. Staying actively engaged in monitoring health changes is essential.

Some patients may undergo periodic imaging tests to evaluate how well fulvestrant is keeping the cancer stable. If the cancer begins growing again despite fulvestrant, the oncologist will discuss adjusting therapy.

How long is treatment continued?

There is no set limit on treatment duration with fulvestrant. The goal is controlling advanced cancer while minimizing impact on quality of life. As long as the cancer remains stable and side effects are tolerable, monthly injections can continue for months or years.

If the cancer worsens on fulvestrant, next steps depend on the specific situation:

  • Trying fulvestrant combined with targeted therapy or chemotherapy
  • Adjusting the fulvestrant dose
  • Switching to another hormone therapy
  • Discontinuing oral hormone therapy medications being used with fulvestrant
  • Stopping fulvestrant and initiating different therapy

For those with extensive progression after multiple treatments, hospice care may be recommended for comfort and support. The treatment team helps determine the best plan.

The key is weighing benefits against downsides, and adjusting course early if problems arise. Staying on top of monitoring and speaking up about symptoms allows for adapting treatment plans promptly.

In conclusion, while not a cure, fulvestrant offers another option for controlling cancer growth long-term for some women with advanced, metastatic estrogen receptor positive breast cancer. As with any cancer treatment, navigating side effects takes effort and speaking up about concerns quickly is vital. Partnering closely with your care team each step of the way provides the greatest chance of success.


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