Treatment effect of palbociclib plus endocrine therapy by prognostic and intrinsic subtype and biomarker analysis in patients with bone-only disease: a joint analysis of PALOMA-2 and PALOMA-3 clinical trials

Richard S. Finn*, Massimo Cristofanilli, Johannes Ettl, Karen A. Gelmon, Marco Colleoni, Carla Giorgetti, Eric Gauthier, Yuan Liu, Dongrui R. Lu, Zhe Zhang, Cynthia Huang Bartlett, Dennis J. Slamon, Nicholas C. Turner, Hope S. Rugo

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

Purpose: This analysis evaluated the relationship between treatment-free interval (TFI, in PALOMA-2)/disease-free interval (DFI, in PALOMA-3) and progression-free survival (PFS) and overall survival (OS, in PALOMA-3), treatment effect in patients with bone-only disease, and whether intrinsic subtype affects PFS in patients receiving palbociclib. Methods: Data were from phase 3, randomized PALOMA-2 and PALOMA-3 clinical studies of hormone receptor‒positive/human epidermal growth factor receptor 2‒negative (HR+ /HER2−) advanced breast cancer (ABC) patients receiving endocrine therapy plus palbociclib or placebo. Subpopulation treatment effect pattern plot (STEPP) analysis evaluated the association between DFI and PFS and OS. PFS by luminal subtype and cyclin-dependent kinase (CDK) 4/6 or endocrine pathway gene expression levels were evaluated in patients with bone-only disease; median PFS and OS were estimated by the Kaplan–Meier method. Results: Median durations of TFI were 37.1 and 30.9 months (PALOMA-2) and DFI were 49.2 and 52.0 months (PALOMA-3) in the palbociclib and placebo groups, respectively. Among the PALOMA-2 biomarker population (n = 454), 23% had bone-only disease; median PFS was longer with palbociclib versus placebo (31.3 vs 11.2 months; hazard ratio, 0.41; 95% CI 0.25‒0.69). The interaction effect of bone-only versus visceral disease subgroups on median PFS with palbociclib was not significant (P = 0.262). Among the PALOMA-3 biomarker population (n = 302), 27% had bone-only disease. STEPP analyses showed that palbociclib PFS benefit was not affected by DFI, and that palbociclib OS effect may be smaller in patients with short DFIs. Among patients who provided metastatic tumor tissues (n = 142), regardless of luminal A (hazard ratio, 0.23; 95% CI 0.11‒0.47; P = 0.0000158) or luminal B (hazard ratio, 0.26; 95% CI 0.12‒0.56; P = 0.000269) subtype, palbociclib improved PFS versus placebo. Conclusions: These findings support palbociclib plus endocrine therapy as standard of care for HR+ /HER2− ABC patients, regardless of baseline TFI/DFI or intrinsic molecular subtype, including patients with bone-only disease. Trial registration: Pfizer (clinicaltrials.gov:NCT01740427, NCT01942135).

Original languageEnglish (US)
Pages (from-to)23-35
Number of pages13
JournalBreast Cancer Research and Treatment
Volume184
Issue number1
DOIs
StatePublished - Nov 1 2020

Keywords

  • Bone-only disease
  • Disease-free interval
  • Intrinsic subtype
  • Palbociclib
  • Treatment-free interval

ASJC Scopus subject areas

  • Oncology
  • Cancer Research

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