11 Real-world Treatment Patterns and Effectiveness of Palbociclib Plus an Aromatase Inhibitor in Patients With Metastatic Breast Cancer Aged 75 Years or Above

Background

Data on treatment patterns and comparative effectiveness of palbociclib (PB) in older patients with HR+/HER2– MBC are limited. This study described dose patterns of PB and compare effectiveness of first-line (1L) PB+AI vs AI in patients aged ≥75 years in US routine clinical practice.

Materials and Methods

This retrospective analysis used the Flatiron Health nationwide longitudinal database to identify female and male patients aged ≥75 years with HR+/HER2– MBC who started PB+AI or AI as 1L therapy between February 2015 and March 2020. Patients were evaluated from start of PB+AI or AI to September 2020, death, or last visit, whichever came first. Overall survival (OS) was defined as the months from start of PB+AI or AI to death. Real-world progression-free survival (rwPFS) was defined as the months from start of PB+AI or AI to death or disease progression. Patient characteristics were balanced using stabilized inverse probability of treatment weighting (sIPTW) and propensity score matching (PSM).

Table.

Results

Of the 961 patients identified, 313 received PB+AI and 648 received AI alone. The median age was 80.0 years. Key patient characteristics and effectiveness results are presented in the Table. Among 306 PB+AI patients with documented PB starting dose, 75.2% started PB at 125 mg/day
and 39.5% experienced dose adjustment. Median OS in PB+AI vs AI patients was 47.8 vs 31.8 months (mo) (hazard ratio [HR]=0.60, P<.001) in the unadjusted analysis, 43.0 vs 32.4 mo (HR=0.66, P<.001) after sIPTW, and 49.0 vs 37.3 mo (HR=0.64, P<.01) after PSM. Median rwPFS was significantly (P<.01) prolonged in PB+AI vs AI patients in the unadjusted analysis (HR=0.69), after sIPTW (HR=0.72) and PSM (HR=0.73).

Conclusions

PB dose adjustments were experienced by nearly 40% of patients aged ≥75 years with HR+/HER2– MBC in this analysis. First-line PB+AI was associated with prolonged OS and rwPFS compared with AI alone.

AFFILIATIONS:

Adam Brufsky,¹ Xianchen Liu,² Benjamin Li,² Lynn McRoy,² Connie Chen,² Rachel M. Layman,³ Hope S. Rugo⁴

¹UPMC Hillman Cancer Center, University of Pittsburgh Medical Center, Pittsburgh, PA.

²Pfizer Inc, New York, NY.

³The University of Texas MD Anderson Cancer Center, Houston, TX.

⁴University of California San Francisco Helen Diller Family Comprehensive Cancer Center, San Francisco, CA.