What is the standard dose of palbociclib (Ibrance) for breast cancer treatment?

Standard Dose of Palbociclib for Breast Cancer Treatment

The standard dose of palbociclib (Ibrance) is 125 mg taken orally once daily for 21 consecutive days followed by 7 days off treatment to complete a 28-day cycle. 1

Dosing Schedule and Administration Details

• Palbociclib should be administered with food 1
• The medication is taken as part of a complete 28-day cycle:
  • 21 days ON (taking the medication)
  • 7 days OFF (no medication)
• Capsules should be swallowed whole (do not chew, crush, or open) 1
• Patients should take their dose at approximately the same time each day 1

Combination Therapy Requirements

Palbociclib is indicated for use in combination with:

• An aromatase inhibitor as initial endocrine-based therapy, OR
• Fulvestrant in patients with disease progression following endocrine therapy 1

When given with fulvestrant, the recommended dose of fulvestrant is 500 mg administered on Days 1,15,29, and once monthly thereafter 1

Monitoring Requirements

Blood count monitoring is essential due to the risk of neutropenia:

• Complete blood counts should be monitored prior to starting therapy
• At the beginning of each cycle
• On Day 15 of the first two cycles
• As clinically indicated thereafter 1, 2
• For patients who experience only Grade 1-2 neutropenia in the first 6 cycles, subsequent monitoring can be reduced to every 3 months 1

Dose Modifications

Dose reductions may be necessary based on individual tolerability and adverse events:

• First dose reduction: 100 mg/day
• Second dose reduction: 75 mg/day
• If further reduction below 75 mg/day is required, discontinue treatment 1

The most common reason for dose modification is neutropenia, which should be managed according to the following guidelines:

• Grade 3 neutropenia: Consider dose delays and reductions for prolonged recovery
• Grade 3 neutropenia with fever ≥38.5°C and/or infection: Withhold until recovery to Grade ≤2, then resume at next lower dose
• Grade 4 neutropenia: Withhold until recovery to Grade ≤2, then resume at next lower dose 1, 2

Special Populations

• Pre/perimenopausal women receiving palbociclib with an aromatase inhibitor or fulvestrant should also receive LHRH agonist therapy 1
• Men receiving palbociclib plus aromatase inhibitor therapy should consider LHRH agonist treatment 1

Common Adverse Events

The most frequent adverse reactions include:

• Neutropenia (most common, reported in up to 66.7% of patients) 3
• Fatigue (35.3%) 3
• Stomatitis (26.6%) 3
• Leukopenia 1

Important Clinical Considerations

• Febrile neutropenia is relatively uncommon (reported in only 2.4% of patients in one study) 3
• Quality of life is generally maintained throughout treatment 3
• The addition of palbociclib to endocrine therapy has been shown to significantly improve progression-free survival in metastatic breast cancer 4
• Discontinuation rates due to adverse events are relatively low (approximately 3.2%) 3

Remember that while palbociclib has shown benefit in the metastatic setting, it has not demonstrated efficacy in the adjuvant setting based on the PALLAS trial, which showed no improvement in invasive disease-free survival when added to adjuvant endocrine therapy 5.