Abstract: Objective To evaluate the efficacy and safety of Palbociclib combined with endocrine therapy for HR+ /HER2- advanced breast cancer (ABC). Methods The clinical data of 83 patients with HR+ /HER2- ABC in our center from September 15, 2018 to October 30, 2020 were retrospectively analyzed to evaluate the clinical efficacy, progression-free survival (PFS) and adverse effects of Palbociclib combined with endocrine therapy. Results A total of 83 patients with HR+ /HER2- ABC were enrolled and the median follow-up time was 15.5 months. The ORR of the first-line patients (n=25) and the second-line patients (n=38) received Palbociclib combined with endocrine therapy were higher than those of the multi-line patients (n=20), but the difference was not statistically significant (48.0% vs 44.7% vs 30.0%, P=0.466), and there was no statistically significant difference in DCR among the three groups (96.0% vs 89.5% vs 80.0%, P=0.337). The median progression-free survival (mPFS) in the Palbociclib combined group was 13.0 months (95%CI: 11.4 to 14.6 months), the first-line/the second-line patients had longer mPFS than the multi-line patients (20.0 months vs 14.0 months vs 5.0 months, P<0.001), and only the bone metastases patients had better mPFS than patients without bone metastases (NR months vs 13.0 months; HR=0.42, 95%CI: 0.22-0.84, P=0.01); mPFS in patients without visceral metastasis was better than those with visceral metastasis, but the difference was not statistically significant (20.0 months  vs 13.0 months; HR=0.65, 95%CI: 0.35-1.22, P=0.38). Patients who were resistant to Everolimus combined with endocrine therapy still benefited from Palbociclib (mPFS=5 months). The most common and serious adverse effects of 83 patients received Palbociclib combined were neutropenia, among which 12 patients were dose-reduced due to adverse effects. Conclusions Palbociclib combined with endocrine therapy for HR+ /HER2- ABC patients has a significant clinical efficacy and good safety, especially the first-line /the second-line treatment has achienved good efficacy.

Key words: Breast cancer, Palbociclib, Endocrine therapy, Hormone receptor-positive