Breast Cancer Breast Cancer Metastatic Palbociclib Side Effects Targeted Therapies Treatments Uncategorized

Palbociclib Side Effects

Palbociclib Side Effects & Patient Stories

Palbociclib isn’t a traditional form of chemotherapy. It’s a targeted therapy that must be taken in combination with certain hormonal therapies like aromatase inhibitors and fulvestrant and which is aimed at specific kinds of breast cancer cells.

Palbociclib, commercially known as IBRANCE, is a treatment for a specific kind of metastatic breast cancer, or breast cancer that has already spread to other parts of the body, known as HR+/HER2- mBC. Palbociclib may be able to renew patients’ hope and offer them a greater sense of possibility.

Are you a HR+/HER2- mBC patient who is considering taking palbociclib, or is about to start taking it? In this article, we provide key information about palbociclib to help you and other patients prepare to take this therapy, including what to tell your doctor before you begin; also tell you about the side effects you might experience when taking it; and provide links to a couple of real-life patient experiences shared by patients who have used palbociclib as part of their cancer treatment.

What is palbociclib, and what is it used for?

Palbociclib is a kind of cancer medicine called a CDK 4/6 inhibitor that’s prescribed for a specific type of metastatic breast cancer known as HR+/HER2- mBC. Pfizer, IBRANCE manufacturer, describes it as a “first-of-its-kind treatment” for patients with this kind of cancer.

Is palbociclib chemotherapy?

Palbociclib isn’t a traditional form of chemotherapy. It’s a targeted therapy that must be taken in combination with certain hormonal therapies like aromatase inhibitors and fulvestrant and which is aimed at specific kinds of breast cancer cells.

“My first line of treatment in 2017 was IBRANCE, which was approved by the FDA in 2015. I was able to be on a medication that had just recently been approved by the FDA, which is huge.   That line or that class of drugs, the CDK4/6 inhibitors, has really changed the landscape of breast cancer. Starting in 2015 with IBRANCE, and then there’s now a fourth one that’s being added to that class. People are living a whole lot longer with far less side effects.”

Abigail, Stage 4 Metastatic Breast Cancer

What are CDK 4/6 inhibitors?

CDK 4/6 inhibitors are cancer treatments that disrupt how breast cancer cells divide and multiply. To do so, these treatments target specific proteins called cyclin-dependent kinases 4 and 6, or CDK 4/6 for short. 

CDK 4/6 proteins are found in both healthy cells and cancer cells, and control how quickly these cells grow and divide. In breast cancer, these proteins can cause cancer cells to grow and divide wildly. CDK 4/6 inhibitors target these proteins with the aim of slowing down or even stopping cancer cells growth altogether. This is why palbociclib and the other CDK 4/6 inhibitors, KISQUALI (ribociclib) and VERZENIO (abemaciclib), are known as targeted therapies.

How and when is palbociclib used?

Palbociclib is prescribed for hormone-receptor positive (HR+), human epidermal growth factor receptor 2-negative (HER2-) metastatic breast cancer (mBC)—in short, HR+/HER2- mBC. This is the most common subtype of metastatic breast cancer, representing approximately 60% of all breast cancer cases.

The growth of hormone-receptor positive breast cancer cells is supported by one of both of the hormones estrogen or progesterone. And HER2-negative cancers test negative for the HER2 protein, which is another protein that can promote cancer cell growth.

“I’m on a medication called IBRANCE — that’s three weeks on, one week off — and that’s what knocks down my immunity. [Sometimes], I have to take an extra week off because my immunity is too low to continue that one so it’s a little bit of a dance with that one. It’s all working.”

Bethany, Stage 4 Metastatic Breast Cancer

Palbociclib is always prescribed in combination with hormonal therapies such as aromatase inhibitors and fulvestrant. Palbociclib is available in pill form and is taken daily, by mouth and with food. 

Palbociclib is given out in four-week cycles, the last week of which is a week-long break—which means that you’ll need to take it for 21 days straight, followed by a 7-day off-treatment period, to comprise a complete cycle of 28 days.

How much does palbociclib cost?

The cash price for palbociclib, using an online coupon, can be $13,000 to $13,500 for a 21-day supply. Most people won’t be paying this price, though—this is the cash price only, with a discount coupon, and is not valid with insurance plans. The prescription cost may be lower for those who have commercial insurance.

If you’d like to explore getting a copay card or copay assistance, Pfizer can help. The Pfizer Oncology Together Co-Pay Savings Program may help eligible, commercially insured patients save on their out-of-pocket costs. Pfizer Oncology Together can connect patients who are uninsured, underinsured, or have government insurance with resources that may help pay for a prescription.

Palbociclib isn’t currently available in a generic version.

How effective is palbociclib?

Pfizer has shared the results of clinical trials that tested IBRANCE in combination with the aromatase inhibitor letrozole (more than half of the patients involved in the trial saw their tumors shrink in size, versus 44% who took letrozole and a placebo), and in combination with the hormonal therapy fulvestrant (24.6% of these patients saw their tumors shrink vis-a-vis just 10.9% of those who took fulvestrant and a placebo).

What to expect when taking palbociclib

When taking palbociclib, side effects can be expected—some of which are serious. Be sure to share any side effects you may experience with your doctor immediately. Your doctor may interrupt or stop treatment with it completely if any of the symptoms you experience are severe.

Palbociclib side effects

“My first line of treatment after I finished chemo was IBRANCE and letrozole, and I was able to be on that for 2 years. 

“There were very low side effects. Most targeted therapy affects the bone marrow, so we had to watch for low white blood cells, or neutropenia. I was always immunocompromised and having to be careful. The main side effects were the blood counts and some fatigue.”

Abigail, Stage 4 Metastatic Breast Cancer

Palbociclib side effects can include but may not be limited to the following:

  1. Low white blood cell counts (neutropenia) are very common when taking palbociclib and may lead to serious infections. Your white blood cell counts will need to be checked before and during treatment. During treatment, you’ll need to tell your doctor right away if you experience any symptoms of neutropenia or infections such as fever and chills.
  2. Palbociclib may cause lung problems (pneumonitis) stemming from severe inflammation, including chest pain, cough with or without mucus, and trouble breathing or shortness of breath.
  3. Low red blood cell counts and low platelet counts. Make sure to inform your doctor immediately if you bleed or bruise more easily, feel dizzy or weak, and/or experience nosebleeds and shortness of breath while on treatment.
  4. Possible allergic reactions to palbociclib, including hives, difficulty breathing, and swelling of your lips, tongue, face and/or throat.
  5. Fertility problems in male patients.
  6. Tiredness.
  7. Nausea.
  8. Sore mouth.
  9. Abnormalities in liver and blood tests.
  10. Diarrhea.
  11. Hair thinning or hair loss.
  12. Vomiting.
  13. Rashes.
  14. Loss of appetite.

What to tell your doctor or healthcare provider before starting treatment with palbociclib

Before starting treatment, you’ll need to inform your doctor about all your medical conditions, including:

  1. Signs and symptoms of possible infection, such as fever or chills.
  2. Liver or kidney problems.

You’ll also need to tell your doctor if you’re pregnant or planning to get pregnant, or, if you’re male, have a female partner who can get pregnant. Palbociclib can harm unborn babies.

  1. Female patients who can become pregnant will need to take effective birth control for the duration of their treatment and up to three weeks after its final dose.
  2. Male patients with female partners who can become pregnant will need to use effective birth control during treatment and for at least 3 months after taking their final dose.

Lastly, it would be good to determine if you’re allergic to palbociclib before you start taking it.

Foods to avoid while on palbociclib

Do not eat foods containing grapefruit or drink grapefruit juice while on this treatment. According to Pfizer, they may actually increase the amount of palbociclib in your bloodstream.

Stories of patients taking palbociclib

Stacy S.

Stacy S.

Diagnosis: Myelofibrosis with CALR and ASXL1 mutations
Symptoms: Fatique, cold hands and feet
Treatment: Agrylin (for thrombocythemia), Ruxolitinib (Jakafi), Fedratinib (INREBIC), stem cell transplant
Ruth R. Diagnosis: Myeloproliferative Neoplasms (MPN) Treatment: Chemotherapy, Bone marrow biopsy, clinical trial
Natalia's Myelofibrosis Story
Natalia A. Diagnosis: Myelofibrosis Symptoms: Anemia, fatigue, weakness, shortness of breath Treatment: Phlebotomies, iron pills, blood transfusion

Mary L.

Diagnosis: Myelofibrosis (MPN)
1st Symptoms: Fatigue, extreme dizziness (later diagnosed as vertigo)
Treatment: Pegasys, hydroxyurea (current)
Kristin D.

Kristin D.

Symptoms: None; caught at routine blood work
Treatment: Stem cell transplant
Joseph C. feature profile

Joseph C.

Symptoms: None; caught at routine blood work
Treatment: Clinical trial: VONJO (pacritinib)

Jeremy S.

Diagnosis: Myeloproliferative Neoplasm (MPN), Polycythemia vera (PV) and Chronic Lymphocytic Leukemia (CLL)

Doug A. feature profile

Doug A.

Symptoms: Fatigue
Treatment: ruxolitinib, selinexor (clinical trial)
Cathy T. feature profile

Cathy T.

Diagnosis: Myelofibrosis

Symptoms: None; caught at a routine blood test
Treatment: Stem cell transplant
Andrew SchorrDiagnosis: Myelofibrosis, Chronic Lymphocytic Leukemia (CLL)Treatment: Clinical trial, Gazyva, Jakafi, Increbic, Reblozyl and steroids



U.S. Food and Drug Administration (FDA)

National Cancer Institute (NIH)

The Mayo Clinic



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