Palbociclib for Hormone-Receptor–Positive, HER2-Positive Advanced Breast Cancer
Otto Metzger, Sumithra Mandrekar, S. Goel, J. Gligorov, E. Lim, Eva Ciruelos, Sibylle Loibl, Travis Dockter, Xavier Gonzàlez Farré, Prudence A. Francis, F. Lynce, J Lanzillotti, Carter DuFrane, Anna Wall, Carrie Strand, Ian Krop, Ines Vaz-Luis, Debu Tripathy, Sherene Loi, A. Prat, Matthew Goetz, Santiago Escrivá-de-Romaní, David Porter, Jennifer Spoenlein, Daniel G. Stover, Sagar Sardesai, Pierre-Etienne Heudel, María Koehler, Cynthia Huang Bartlett, Ariadna Holynskyj, Prashanth Gopalakrishna, Eric Gauthier, Suzette Delaloge, Kathy Miller, Eric P. Winer, Luca Gianni, Ann H. Partridge, A DeMichele, L.A. Carey
Abstract
BACKGROUND: Dual anti-human epidermal growth factor receptor 2 (HER2) therapy plus chemotherapy followed by maintenance treatment with HER2-targeted and endocrine therapies is standard first-line treatment for hormone-receptor-positive, HER2-positive metastatic breast cancer. On the basis of preclinical and clinical data, the addition of palbociclib (a selective inhibitor of cyclin-dependent kinases 4 and 6) may overcome resistance to both endocrine and HER2-directed therapies. METHODS: In this phase 3, open-label, randomized trial, we enrolled patients with hormone-receptor-positive, HER2-positive metastatic breast cancer who did not have disease progression after four to eight cycles of chemotherapy plus HER2-targeted therapy. Patients were randomly assigned in a 1:1 ratio to receive maintenance HER2-targeted and endocrine therapies with or without palbociclib. The primary end point was investigator-assessed progression-free survival. Secondary end points included the objective response, clinical benefit, safety, and overall survival. RESULTS: A total of 518 patients underwent randomization: 261 were assigned to receive palbociclib and 257 to receive standard therapy. At a median follow-up of 53.5 months, patients in the palbociclib group had significantly longer progression-free survival than those in the standard-therapy group (median duration, 44.3 months vs. 29.1 months; hazard ratio for disease progression or death, 0.75; 95% confidence interval, 0.59 to 0.96; two-sided P = 0.02). Grade 3 and 4 adverse events, predominantly from neutropenia, occurred in 79.7% and 10.0% of the patients, respectively, in the palbociclib group, as compared with 30.6% and 3.6% of the patients, respectively, in the standard-therapy group. CONCLUSIONS: The addition of palbociclib to maintenance anti-HER2 and endocrine therapies led to a significant improvement in progression-free survival over standard therapy, with increased toxic effects, mainly neutropenia. (Funded by Pfizer and others; PATINA ClinicalTrials.gov number, NCT02947685.).