Endocrine therapy and palbociclib within a compassionate use program in heavily pretreated hormone receptor-positive, HER2-negative metastatic breast cancer

This is a single center retrospective analysis of patients with hormone receptor-positive, HER2-negative metastatic breast cancer progressing after ≥ 4 treatment lines treated with palbociclib in combination with endocrine therapy within a compassionate use program. Thirty-four patients were included between 10/2015 and 02/2017, the majority (82.4%) being previously treated with mTOR inhibitors. Disease control rate was 52.9% and 24.4% at week 12 and 24. Overall progression-free survival was 3.1 months with no difference between mTOR inhibitor-pretreated (3.5 months) and -naïve patients (2.7 months; hazard ratio, 0.83). Toxicity profile in this population was comparable to that seen in previous trials.