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Treatment Name: Palbociclib (Ibrance®) + Letrozole (Femara®)

Palbociclib (Ibrance®) + Letrozole (Femara®) is a Chemotherapy Regimen for Breast Cancer - metastatic

How does palbociclib + letrozole work?

Palbociclib is designed to inhibit (block) a specific protein that is responsible for turning off tumor suppressor genes and allowing the breast cancer cell to grow and divide.  In other words, by inhibiting (blocking) this protein, palbociclib causes the breast cancer cell to stop actively growing and dividing.

Letrozole is designed to block an enzyme (a type of protein) in your body called aromatase. Aromatase is responsible for helping produce a female hormone known as estradiol (a type of estrogen).

When letrozole inhibits aromatase, there is less estrogen produced. When estrogen is not able to bind to the receptors on breast cancer cells, the breast cancer cells are not able to grow or divide. Patients with breast cancer that are not estrogen-receptor positive may not respond to treatment with letrozole.

Goals of therapy:

Palbociclib + letrozole are taken together to slow the growth of breast cancer and prevent it from spreading further, not for cure.


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How is palbociclib + letrozole therapy for breast cancer taken?

  • Palbociclib usual starting dose: 125 mg oral capsule by mouth daily with food for 21 consecutive days, followed by a 7-day no palbociclib rest period. This “21-Day on, 7-Day off” treatment period is known as one Cycle
  • Letrozole usual starting dose: 2.5 mg oral tablet by mouth once Daily, continuously (no days off)

Palbociclib + letrozole is usually taken at home and is taken until the regimen no longer works or until unacceptable side effects occur. Each cycle is repeated every 28 days.

Note: Letrozole is only indicated for use in post-menopausal women and should not be used by pre-menopausal women.

Side Effects

What are the most common side effects from palbociclib + letrozole for breast cancer?

In a multi-drug regimen, each medication has unique side effects. When these medicines are given together, drug-related side effects reported in clinical studies give the best estimate of what to expect. In clinical studies, the most commonly reported side effects with palbociclib + letrozole are shown here:

Roughly, 7% of patients discontinue palbociclib and 2% of patients discontinue letrozole due to unacceptable side effects. Most symptoms reported above were mild (Grade 1 - 2).

Watch videos on common palbociclib + letrozole therapy side effects below

Side effect videos Side Effect Videos
Fatigue Fatigue AnemiaAnemiaNausea and VomitingNausea and VomitingPainPainHair LossHair LossDiarrheaDiarrheaConstipationConstipationBleedingBleedingBlood ClotsBlood ClotsNeutropenic FeverNeutropenic Fever


How often is monitoring needed?

Labs (blood tests) may be checked before starting treatment, then every 2 weeks during the first two cycles, then monthly thereafter. Labs often include: Complete Blood Count (CBC), Comprehensive Metabolic Panel (CMP), triglycerides, and blood cholesterol levels, plus any others your doctor may order.

How often is imaging needed?

Imaging may be checked before treatment and every two to six months during treatment. Imaging may include: bone scans, magnetic resonance imaging (MRI), and computerized tomography (CT) scans. DEXA (dual energy x-ray absorptiometry) scans may be performed to monitor your bone mineral density

How might blood test results/imaging affect treatment?

Depending upon the results, your doctor may advise to continue palbociclib + letrozole as planned, reduce the dose, delay therapy, or switch therapy.

ChemoExperts Tips

What are the 4 most important things to know about palbociclib and letrozole when receiving treatment?

  • Palbociclib in combination with letrozole may increase your risk of developing blood clots more than with letrozole alone. Go to the emergency room if you experience signs of a pulmonary embolism such as shortness of breath, chest pain, or heart palpitations (rapid, fluttering, or pounding feeling)
  • Do not take estrogen replacement therapy or other medications that contain estrogen as they may decrease the effectiveness of letrozole
  • A pharmacist should ALWAYS review your medication list to ensure that drug interactions are prevented or managed appropriately
  • Clinical trials may exist for breast cancer. Ask your doctor if any studies are currently enrolling in your area. If not, go to to search for other centers offering study medications

Patient Assistance & Co-payment Coverage

Patients under the age of 65 years, or those with private insurance plans:
If you have insurance and are looking for patient assistance or copay assistance for Palbociclib (Ibrance®) + Letrozole (Femara®), we have provided links that may help.

Visit our Patient Assistance page and click the links to various patient assistance programs for help paying for Palbociclib (Ibrance®) + Letrozole (Femara®). Depending upon your income, they may be able to help cover the cost of:

  • Palbociclib
  • Letrozole

For Branded medications (may be available for generic medications too), check with the manufacturer to determine if a co-pay card is offered and if it could reduce your monthly copay.

  • If you are uninsured, check with the manufacturer to determine if you are eligible to receive medication at no cost.

Medicare and Medicaid patients (Patients 65 years or older):
The clinic providing treatment will likely pre-authorize medications and immune therapies such as Palbociclib (Ibrance®) + Letrozole (Femara®) and are the best source to help you understand drug cost.

  • Ask to speak with a patient assistance technician or financial counselor at the clinic or hospital administering this therapy.

Emotional Wellness

What is Emotional Wellness?
Emotional wellness is having a positive outlook balanced with a realistic understanding of current life events. This requires both an awareness and acceptance of your emotions. It is with this knowledge that you can develop a plan to take the necessary actions to positively impact your life.

Emotional wellness uses an ongoing process to continually reflect on the stressors of life in a constructive manner to move forward and create happiness.

Because emotional wellness is deeply connected with physical, social, and spiritual wellness, pursuing it often becomes particularly difficult in times of major illness. Despite this difficulty, working toward emotional wellness has been connected to improved treatment outcomes and a higher likelihood of achieving goals of therapy.

Learn more about pursuing emotional wellness while receiving treatment with Palbociclib (Ibrance®) + Letrozole (Femara®)

Individual Drug Label Information

Palbociclib (Ibrance®)

  • Palbociclib is an oral capsule that comes in strengths of: 125 mg, 100 mg, or 75 mg 
  • Take with food at the same time each day. Do not crush or open capsules. 
  • If you miss a dose, take it as soon as you remember if it’s the same day. If it is the next day, take your regular dose as scheduled. Do not double the dose to make up for the missed dose 
  • If you vomit up a dose, an additional dose should not be taken that day. Take the next dose at the next regular scheduled time 
  • Store at room temperature in a cool, dry place 
  • Dosage adjustments may be required for low white blood cells or other severe side effects 
  • May interact with certain antifungal and seizure medications. Ask your doctor or pharmacist to review your medications for any possible interactions  
  • May interact with grapefruit and grapefruit juice causing increased blood levels of palbociclib. This could increase your risk of experiencing side effects. Avoid eating grapefruit and drinking anything containing grapefruit juice during treatment 
  • Avoid therapy with St. Johns Wort as it will decrease blood levels of palbociclib. This could decrease it’s effectiveness 
  • Avoid during pregnancy. Contact your doctor immediately if you think you may have become pregnant. 
  • Females who are of child bearing age should use contraception during treatment and for at least 2 weeks after stopping palbociclib 
General Palbociclib (Ibrance) Side Effects 
  • Low white blood cells, red blood cells, and platelets are common 
  • Can increase risk for infections such as upper respiratory tract infections 
  • Spontaneous nose bleeds may occur 
  • Nausea and vomiting may occur 
  • May cause diarrhea 
  • May cause mouth sores 
  • Hair loss can occur 
  • May cause tingling or numbness in fingers and toes 
  • Click on the palbociclib (Ibrance) package insert below for reported side effects and possible drug interactions

Side Effect Videos
Nausea and VomitingNausea and VomitingDiarrheaDiarrheaHair LossHair LossFatigue Fatigue BleedingBleedingAnemiaAnemiaBlood ClotsBlood Clots

See DailyMed package insert.

Letrozole (Femara®)

  • Letrozole is an oral tablet 
  • Letrozole can be taken with or without food. Swallow tablets whole and do not crush tablets. If you miss a dose, take the dose as soon as you remember if it is still the same day. If it is the next day, take your regular dose as scheduled. Do not double your dose to make up for the missed dose 
  • Letrozole should be stored at room temperature in a cool, dry place 
  • Dosage adjustments may be required due to side effects or liver dysfunction 
  • May cause fetal harm; avoid pregnancy 
General Letrozole (Femara) Side Effects 
  • One of the most common side effects reported is hot flashes. Talk to your doctor about ways to minimize and treat hot flashes. Do not take any medicines, herbs, or natural supplements without speaking with your doctor or pharmacist first 
  • Joint pain 
  • Decreased bone strength 
  • Increase in blood cholesterol 
  • May cause dizziness and/or drowsiness 
  • High blood pressure 
  • Increase risk of blood clots 
  • Mood swings 
  • Fluid retention 
  • Skin rash 
  • Decreased sexual drive 
  • Nausea and vomiting 
  • Constipation
  • Click on the letrozole (Femara) package insert below for reported side effects and possible drug interactions

Side Effect Videos
Nausea and VomitingNausea and VomitingFatigue Fatigue ConstipationConstipationPainPainBlood ClotsBlood Clots

See DailyMed package insert.

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Finn RS, Crown JP, Lang I, et al. The cyclin-dependent kinase 4/6 inhibitor palbociclib in combination with letrozole versus letrozole alone as first-line treatment of oestrogen receptor-positive, HER2-negative, advanced breast cancer (PALOMA-1/TRIO-18): a randomised phase 2 study. Lancet Oncol. 2015;16:25-35.

Created: February 20, 2016 Updated: September 24, 2018

What is Breast Cancer - metastatic?

What is Metastatic Breast Cancer?
A disease of the milk-producing glands known as lobules, milk ducts, or other cells found in the breast. Metastatic breast cancer is one that has moved from the breast to other areas of the body, which may include the brain, liver, or bone. Breast cancer is one of the most common types of cancers in women, but may rarely affect men as well. Known causes of breast cancer include genetic causes, such as the BRCA mutation, or obesity. The effectiveness of the treatment may depend upon the stage at diagnosis.

Types of metastatic breast cancer:
1. Hormone-receptor positive or negative (60 - 65% of patients)

  • Estrogen Receptor positive (ER)+ or negative (ER)-
  • Progestin Receptor positive (PR)+ or negative (PR)-

2. Hormone Epidermal growth factor Receptor-2 (HER-2) positive or negative (20 - 25% of patients)

  • HER-2 +
  • HER-2 -

3. Triple Negative (15 - 18% of patients)

  • ER- and PR- and (HER-2)-
NOTE: Treatment Options listed below are not all-inclusive. Other treatments may be available. ChemoExperts provides drug information and does not recommend any one treatment over another. Only your Doctor can choose which therapy is appropriate for you.

What is a CBC?

A Complete Blood Count (CBC) is a frequently ordered blood test that tells clinicians the status of your: 1) White blood cell count, 2) Hemoglobin, and 3) Platelet count at the time the test was taken.

Common uses:
1) White blood cell count (WBC): is used to determine infection risk, or response to chemotherapy. Certain chemotherapy agents may harm our good infection-fighting cells. Sometimes chemotherapy may need to be delayed to allow these cells to recover.

2) Hemoglobin: is used to determine if someone is anemic. Anytime the hemoglobin is below 12 g/dL, the person is said to be anemic. Red blood cell transfusions, and sometimes iron can be given to restore the hemoglobin level, but anemia treatment should always aim at treating the underlying cause or condition.

3) Platelet count: is used to determine if the risk of bleeding is increased or if a platelet transfusion is required to prevent bleeding. Certain medications that increase bleeding risk, such as: aspirin, certain chemotherapy agents, and blood thinners, may need to be stopped temporarily until the platelet count is within a safe range.

What is a CMP?

A Comprehensive Metabolic Panel (CMP) is a frequently ordered blood test that tells clinicians the status of your: 1) Electrolytes & Acid/Base status2) Kidney function, 3) Liver function, 4) Blood sugar, and 5) Calcium at the time the test was taken. It is commonly used to monitor liver and kidney function when beginning new medications such as chemotherapy. A total of 14 tests are run simultaneously and are shown below.

Electrolytes & Acid/Base status:
1) Sodium, 2) Potassium, 3) Carbon dioxide, 4) Chloride

Kidney Function:
5) BUN (blood urea nitrogen), 6) Serum creatinine (Scr)

Liver Function:
7) AST, 8) ALT, 9) Total bilirubin, 10) Alk Phos, 11) Albumin, 12) Total protein

Blood sugar:
13) Serum glucose

14) Serum calcium

What does Cure mean?

The word “cure” means there are no cancer cells left in the body and cancer will never come back. Depending on the cancer type and stage, this may be the true goal of therapy. However, it is very difficult to prove all cancer cells are gone. Even though images, like X-rays and MRI’s, and blood tests may not show any signs of cancer, there can be a small amount of cancer cells still left in the body. Because of this, the word “remission” is used more often. This means there are no signs or symptoms of cancer. Patients in remission are followed closely for any signs of cancer returning. Sometimes, more chemotherapy may be given while in remission to prevent the cancer from coming back.

Doctors usually do not consider a patient “cured” until the chance of cancer returning is extremely low. If cancer does return, it usually happens within 5 years of having a remission. Because of this, doctors do not consider a patient cured unless the cancer has not come back within 5 years of remission. The five-year cutoff does not apply to all cancers.