Treatment patterns and clinical outcomes in patients with metastatic breast cancer treated with palbociclib-based therapies: real-world data in the Han population

This study aimed to reveal the treatment patterns and clinical outcomes of diverse palbociclib-based regimens in Han patients with estrogen receptor-positive (ER+) metastatic breast cancer in routine clinical practice.The clinical data of patients with ER+ metastatic breast cancer treated with palbociclib were collected from the National Cancer Center database. The efficacy profile of palbociclib in this Han population was evaluated, especially for various combination regimens. The efficacy of palbociclib-based therapy in patients with prior everolimus treatment was also assessed.A total of 186 patients from 89 cities in 18 provinces in China were enrolled. The median progression-free survival (PFS) was similar among different palbociclib-combined groups ( P = 0.566): 10.0 months (95% confidence interval [CI] 3.8-16.1) in the +exemestane group, 9.7 months (95% CI 6.3-13.1) in the +letrozole group, 7.8 months (95% CI 5.5-10.2) in the +fulvestrant group, 7.2 months (95% CI 3.2-11.3) in the +toremifene group, and 6.1 months (95% CI 1.2-11.0) in the +anastrozole group. Thirty-four patients (18.3%) had received everolimus for their metastatic disease before the prescription of palbociclib. The disease control rate was significantly lower in patients who had received previous everolimus than in the everolimus-naïve group (50.0% vs . 82.2%, P < 0.001). Patients pre-treated with everolimus had significantly worse PFS than those in the everolimus-naïve group (3.4 months vs . 8.8 months, P = 0.001). After propensity score matching, patients pre-treated with everolimus had similar PFS (4.4 months, 95% CI 0.5-8.2) compared with everolimus-naïve patients (6.1 months, 95% CI 4.7-7.5, P = 0.439).Various palbociclib-based regimens have promising efficacy in ER+ metastatic breast cancer in real-world settings, even in patients who had been pre-treated with everolimus.