ASCO20: Evaluating Palbociclib Plus Fulvestrant or Letrozole in Metastatic Breast Cancer
Posted: Monday, June 8, 2020
Seeking to identify the better endocrine agent to combine with palbociclib in the first-line treatment of patients with endocrine-sensitive metastatic breast cancer, a European research team found no improvement in progression-free survival with fulvestrant over letrozole, the primary endpoint of the open-label phase II PARSIFAL trial. Antonio Llombart-Cussac, MD, of Hospital Arnau de Vilanova, Valencia, Spain, and colleagues also noted the 4-year overall survival rate in the two arms, a secondary endpoint, was almost identical. These findings were presented during the ASCO20 Virtual Scientific Program (Abstract 1007).
In the study, 486 patients with estrogen receptor–positive, HER2-negative metastatic breast cancer, with no prior therapy in the advanced setting, were divided 1:1 between the arms. Although the authors state that the combination of the CDK4/6 inhibitor palbociclib plus the aromatase inhibitor letrozole has become a standard first-line treatment in this population, other research has shown the antiestrogen agent fulvestrant to be superior to anastrozole.
At a median follow-up of 32 months, the median progression-free survival was 27.9 months with fulvestrant versus 32.8 months with letrozole (P = .321 ). “No differences were observed for patients with or without visceral involvement and for ‘de novo’ or recurrent metastatic disease,” stated Dr. Llombart-Cussac and co-investigators. Of note, the 4-year overall survival rate in the two arms was 67.6% with fulvestrant and 67.5% with letrozole (P = .986). Grade ≥ 3 adverse events were similar in the arms as well, with neutropenia and leukopenia being the most frequent.
“Palbociclib plus fulvestrant is a reasonable alternative to palbociclib plus letrozole in this setting,” they concluded.
Disclosure: The study authors’ disclosure information can be found at coi.asco.org.
