Second-line endocrine therapy (ET) with or without palbociclib (P) maintenance in patients (pts) with hormone receptor-positive (HR[+])/human epidermal growth factor receptor 2-negative (HER2[-]) advanced breast cancer (ABC): PALMIRA trial.

• DOI: 10.1200/jco.2023.41.16_suppl.1001
• Publication Date: 2023-06-04T14:10:33Z
• Authors: Antonio Llombart-...; Catherine Harper-...; Antonia Perello; Audrey Hennequin; Adela Fernandez; Marco Colleoni; Vicente Carañana; Vanesa Quiroga; Jacques Medioni; Vega Iranzo; Duncan Wheatley; Sonia Del Barco; Antonio Anton; Erion Dobi; Manuel Ruiz-Borrego; Daniel Alcalá-López; Jhudit Pérez-Escu...; Miguel Sampayo-Co...; José Manuel Pérez...; Javier Cortes
• Keywords: Palbociclib; Letrozole; Fulvestrant; Clinical endpoint; Progression-free survival; Regimen

1001 Background: Cyclin-dependent kinases 4 and 6 inhibitors (CDK4/6i) in combination with ET has become a standard first-line treatment for pts endocrine-sensitive, HR[+]/HER2[-] ABC. The optimal after progression on CDK4/6i remains unknown. This study aims to determine if P maintenance an alternative improves the antitumor activity of second-line this patient population. Methods: A total 198 ABC who had disease plus (aromatase inhibitor or fulvestrant) were included. Pts eligible they clinical benefit defined as response stable ≥24 weeks, progressed P-based regimen adjuvant setting at least 12 months but no more than following completion. randomly assigned (2:1 ratio) receive (letrozole fulvestrant, based prior ET) alone. Stratification factors presence visceral involvement. Primary endpoint was investigator-assessed progression-free survival (PFS) determined by RECIST v.1.1. Secondary endpoints included overall rate (ORR), (CBR), survival, safety. 2-sided log-rank test (α = 0.05) 80% power detect hazard ratio ≤0.59 favor maintenance. Results: Between April 2019 October 2022, 136 62 randomized P+ET ET, respectively. characteristics well balanced. Median age 59 years (range: 33-85), 61.1% ECOG 0, disease, 89.9% received aromatase + metastatic disease. At median follow-up 8.7 155 PFS events, 4.2 (95% CI 3.5–5.8) vs. 3.6 2.7–4.2) arm (hazard 0.8, 95% 0.6–1.1, p=0.206). result consistent across all stratification subgroups. 6-month 40.9% 28.6% Among 138 measurable significant differences observed ORR (6.4% 2.3%) CBR (33.0% 29.5%) Grade 3-4 adverse events higher treated (45.2% 8.3%) new safety signals identified. No treatment-related deaths reported. Conclusions: For pts, maintaining beyond therapy did not significantly improve compared Planned biomarker analysis may help identify which are likely from therapeutic approach. Clinical trial information: NCT03809988 .