Published in:
01-09-2020 | Breast Cancer | Clinical trial
Impact of early dose intensity reduction of Palbociclib on clinical outcomes in patients with hormone-receptor-positive metastatic breast cancer
Published in: Breast Cancer Research and Treatment | Issue 2/2020
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Background
Palbociclib is commonly added to an aromatase inhibitor (AI) as first-line therapy in ER + HER2- metastatic breast cancer (MBC). There are no data on the effect of the relative dose intensity (RDI) of palbociclib in first-line setting on clinical outcomes. The objective of this study is to explore the association of RDI and dose reduction of palbociclib in the first-line setting with PFS.
Methods
This is a retrospective study of ER + HER2- MBC patients who received palbociclib plus AI in first-line setting. Subjects ≥ 18 years old with MBC, who were started on palbociclib 125 mg daily, had completed ≥ 1 cycle of palbociclib, and did not progress within the first 12 weeks were eligible. Analyses were performed at 12- and 36-week landmarks (LM). RDI was defined as the total amount of palbociclib taken per the total amount planned. RDI-high-12 and RDI-low-12 cohorts were defined as patients receiving palbociclib with RDI ≥ 80% and RDI < 80% during the first 12 weeks, respectively. Reduction-12 and No-reduction-12 cohorts were defined as patients who had any dose reduction and patients who had no reduction during the first 12 weeks, respectively.
Results
56 patients were eligible. Kaplan–Meier analysis from 12-week LM showed a median PFS of 17.1 months in RDI-high-12 versus 6.8 months in RDI-low-12 cohort (p = 0.0006). There was a 7.0-month improvement in median PFS in No-reduction-12 versus Reduction-12 cohort (p = 0.0638). Median PFS at 36-week LM was not reached in RDI-high-36 versus 8.6 months in RDI-low-36 cohort (p = 0.0703).
Conclusions
RDI < 80% of palbociclib during the first 12 weeks, when used in combination with an AI in first-line setting in ER + HER2- MBC, is associated with significantly shorter PFS compared to RDI ≥ 80%. There is a trend towards shorter PFS among patients with RDI < 80% versus RDI ≥ 80% at 36 weeks. A larger study is needed to validate these findings.