The U.S. Food and Drug Administration (FDA) has granted accelerated approval to Ibrance (palbociclib), in combination with letrozole, for the treatment of postmenopausal women with estrogen receptor (ER)-positive, human epidermal growth factor receptor (HER2)-negative metastatic breast cancer who have not been previously treated with endocrine-based therapy.

Approval is based on a phase II study that included 165 postmenopausal women with ER-positive, HER2-negative metastatic breast cancer who had not received prior therapy for metastatic disease.

Results showed that participants treated with palbociclib plus letrozole had a progression-free survival 10 months longer than those treated with letrozole alone.

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The most common adverse events observed with palbociclib treatment were neutropenia, leukopenia, fatigue, anemia, upper respiratory tract infections, nausea, stomatitis, alopecia, diarrhea, thrombocytopenia, decreased appetite, vomiting, asthenia, peripheral neuropathy, and epistaxis.

Patients recommended for treatment with Ibrance should receive 125mg orally daily in combination with letrozole, an aromatase inhibitor, 2.5mg orally daily for 21 days, followed by 7 days off, for each 28-day cycle.

RELATED: Palbociclib Improves PFS in ER-Positive, HER2-Negative Breast Cancer

Healthcare professionals should monitor complete blood count prior to initiating treatment, at the beginning of each cycle, and on Day 14 of the first two cycles.

Ibrance works by inhibiting cyclin-dependent kinases (CDKs) 4 and 6, which play a role in promoting cancer cell growth.