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. 2023 Jun:69:375-381.
doi: 10.1016/j.breast.2023.03.015. Epub 2023 Mar 27.

Real-world comparative effectiveness of palbociclib plus letrozole versus letrozole in older patients with metastatic breast cancer

Hope S Rugo  1 , Xianchen Liu  2 , Benjamin Li  2 , Lynn McRoy  2 , Rachel M Layman  3 , Adam Brufsky  4
Affiliations

Real-world comparative effectiveness of palbociclib plus letrozole versus letrozole in older patients with metastatic breast cancer

Hope S Rugo et al. Breast. 2023 Jun.

Abstract

Background: Palbociclib, the first available cyclin-dependent kinase 4/6 inhibitor, plus endocrine therapy is approved for hormone receptor-positive/human epidermal growth factor receptor 2-negative (HR+/HER2-) metastatic breast cancer (MBC). This study compared real-world effectiveness of palbociclib plus letrozole versus letrozole in older patients with MBC in US clinical practice.

Methods: This retrospective analysis included patients from the Flatiron Health longitudinal database. Overall, 796 women with HR+/HER2- MBC aged ≥65 years starting palbociclib plus letrozole or letrozole as first-line therapy between February 2015 and September 2018 were included. Patients were evaluated from treatment start until December 2018, death, or last visit, whichever came first. Real-world progression-free survival (rwPFS), overall survival (OS), and real-world best tumor responses (rwBTR) were endpoints. Stabilized inverse probability treatment weighting (sIPTW) balanced patient characteristics.

Results: After sIPTW, 450 patients treated with palbociclib plus letrozole and 335 treated with letrozole were included; median age was 74.0 years. Median rwPFS was 22.2 (95% CI, 20.0-30.4) months for palbociclib plus letrozole versus 15.8 (12.9-18.9) months for letrozole (hazard ratio, 0.59 [0.47-0.74]; P<0.001). Median OS was not reached for palbociclib plus letrozole versus 43.4 months (30.0-not estimable) with letrozole (hazard ratio, 0.55 [0.42-0.72]; P<0.001). No interactions between age groups (65-74 and ≥75 years) and treatment groups were observed for rwPFS or OS. Rate of rwBTR was significantly higher for palbociclib plus letrozole (52.4%) versus letrozole (22.1%; odds ratio, 2.0 [1.4-2.7]; P<0.001).

Conclusion: This analysis demonstrates the effectiveness of palbociclib combination therapy as standard-of-care for older patients with HR+/HER2- MBC in the first-line setting.

Keywords: Letrozole; Metastatic breast cancer; Palbociclib; Real-world.

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Conflict of interest statement

Declaration of competing interest Hope S. Rugo reports sponsored research to her institution from Pfizer Inc, Merck, Novartis, Eli Lilly, Roche, Daiichi-Sankyo, Seattle Genetics, Macrogenics, Sermonix, Boehringer Ingelheim, Polyphor, AstraZeneca, Ayala, and Gilead and honoraria from PUMA, Samsung, and Mylan. Rachel M. Layman has received research funding to her institution from Pfizer Inc, Eli Lilly, Novartis, GlaxoSmithKline, Puma, Zentalis, and Celcuity; and advisory board/consulting fees from Eli Lilly, Novartis, and Celcuity. Adam Brufsky has received consulting fees from Pfizer Inc, Lilly, Novartis, Eisai, AstraZeneca, Roche, Daiichi, and Merck. Xianchen Liu, Benjamin Li, and Lynn McRoy are employees of and own stock in Pfizer Inc.

Figures

Fig. 1
Fig. 1
Kaplan-Meier curves of real-world progression-free survival in the (A) unadjusted and (B) sIPTW-adjusted analyses. LET = letrozole; PAL = palbociclib; PFS = progression-free survival; sIPTW = stabilized inverse probability treatment weighting.
Fig. 2
Fig. 2
Kaplan-Meier curves of overall survival in the (A) unadjusted and (B) sIPTW-adjusted analyses. LET = letrozole; NE = not estimable; OS = overall survival; PAL = palbociclib; sIPTW = stabilized inverse probability treatment weighting.
Fig. 3
Fig. 3
Forest plots of unadjusted (A) real-world progression-free survival and (B) overall survival by age group; LET = letrozole; PAL = palbociclib; y = years.
See this image and copyright information in PMC

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