The editorial outlines the role of palbociclib, the first CDK4/6 inhibitor to be approved for the treatment of breast cancer, in endocrine-resistant breast cancer. As reported in the same issue of the Journal, the drug, when added to fulvestrant in the phase 3 PALOMA 3 trial, has shown promising results in patients with endocrine-resistant breast cancer.
Yet, Carey and Perou present compelling reasons to proceed with caution. In the editorial, the two present the position that ER-positive breast cancer is biologically heterogeneous, and many patients do well with minimal treatment over time, and using palbociclib adds considerable cost and toxicity to the treatment regimen.
"Ideally, we should seek to identify patients with an excellent prognosis with endocrine therapy alone as well as predictive biomarkers for palbociclib to have a benefit," Carey and Perou write in their editorial. Given the lack of biomarker selectively for palbociclib, the population cannot be sufficiently narrowed to those who may derive the most benefit, Carey recently told Medscape Medical News.