Abstract 223P
Background
Cyclin-dependent kinase 4/6 inhibitors (CDK4/6is) combined with endocrine therapy are the standard of care for patients with hormone receptor-positive (HR+)/human epidermal growth factor receptor 2-negative (HER2−) mBC. However, real-world comparative effectiveness of CDK4/6is plus an AI versus an AI alone for patients with visceral metastases are limited.
Methods
This retrospective study used electronic health records from the US Flatiron Health database. The study included women and men with HR+/HER2− mBC and lung or liver metastases treated with first-line (1L) Pal plus an AI or an AI alone between February 2015 to March 2020 in routine clinical practice with a data cutoff date of September 2020. Patient characteristics were balanced between each treatment cohort by stabilized inverse-probability treatment weighting (sIPTW) and propensity score matching (PSM) as a sensitivity analysis. The weighted Cox proportional hazards model was used to compute hazard ratios (HR) and 95% CIs for overall survival (OS) and real-world progression-free survival (rwPFS).
Results
This study included 891 patients total (n = 622 with lung metastasis, n = 376 with liver metastasis, and n = 107 with both). Pal + AI was associated with prolonged OS and rwPFS in mBC patients with lung and liver metastases (Table); PSM results were consistent with these findings. For all 891 patients with lung or liver metastases, OS and rwPFS were significantly prolonged in the Pal + AI group versus AI alone group following sIPTW (HR = 0.64; P<0.001 and 0.57; P<0.001, respectively).
Conclusions
Pal + AI versus an AI alone demonstrated prolonged OS and rwPFS in routine practice, supporting the use of 1L Pal + AI for patients with HR+/HER2− mBC with visceral metastatic diseases.
Table: 223P
| Metastatic Site and Outcome, months (95% CI) | Pal + AI | AI Alone | Hazard Ratio (95% CI) P value | |
| Lung | n = 326 | n = 296 | ||
| Median | OSa | NR (46.9–NR) | 34.2 (29.1–46.0) | 0.58 (0.46–0.75) P<0.001 |
| OSb | NR (46.9–NR) | 35.7 (30.3–50.8) | 0.62 (0.48–0.81) P<0.001 | |
| rwPFSa | 18.9 (15.0–24.4) | 12.9 (10.6–16.2) | 0.57 (0.46–0.70) P<0.001 | |
| rwPFSb | 20.2 (15.7–27.3) | 13.5 (10.5–17.4) | 0.55 (0.44–0.69) P<0.001 | |
| Liver | n = 211 | n = 165 | ||
| Median | OSa | 31.2 (25.6–37.8) | 17.6 (13.0–22.6) | 0.63 (0.48–0.83) P=0.001 |
| OSb | 31.4 (25.1–37.8) | 21.4 (14.8–31.6) | 0.73 (0.52–1.01) P=0.056 | |
| rwPFSa | 9.7 (7.8–11.1) | 5.5 (3.6–7.9) | 0.58 (0.44–0.76) P<0.001 | |
| rwPFSb | 9.9 (7.5–11.5) | 5.6 (3.4–8.7) | 0.57 (0.42–0.77) P<0.001 |
aUnadjusted; bafter sIPTW; NR, not reached.
Editorial acknowledgement
Editorial support, conducted in accordance with Good Publication Practice (GPP3) and the International Committee of Medical Journal Editors (ICMJE) guidelines, was provided by Kevin Woolfrey, PhD of Oxford PharmaGenesis, Inc., Newtown, PA, USA with funding provided by Pfizer Inc.
Legal entity responsible for the study
Pfizer Inc.
Funding
Pfizer Inc.
Disclosure
A. Brufsky: Financial Interests, Personal, Advisory Board, reports advisory/consultancy fees from AstraZeneca, Pfizer Inc., Novartis, Lilly, Genentech/Roche, Seagen, Daiichi Sankyo, Merck, Agendia, Sanofi, and Puma and research support from Agendia and AstraZeneca. X. Liu, B. Li, L. McRoy, C. Chen: Financial Interests, Personal, Stocks/Shares, are employees of and stockholders: Pfizer Inc. R.M. Layman: Financial Interests, Personal, Advisory Board, reports advisory/consultancy fees from Novartis, Lilly, and Celcuity, and research/grant funding from Pfizer Inc., Novartis, Lilly, GlaxoSmithKline, Zentalis, Puma, and Celcuity. H.S. Rugo: Financial Interests, Personal, Other, reports sponsored research to her institution from Pfizer Inc., Merck, Novartis, Lilly, Roche, Daiichi Sankyo, Seagen, Macrogenics, Sermonix, Boehringer Ingelheim, Polyphor, AstraZeneca, Ayala, and Gilead and honoraria from PUMA, Samsung, and Mylan.