Palbociclib combined with endocrine therapy in heavily pretreated HR+/HER2(-) advanced breast cancer patients: Results from the compassionate use program in Spain (PALBOCOMP)

Abstract

Background: This study evaluated efficacy and safety of palbociclib, a CDK4/6 inhibitor, in heavilypretreated hormone receptor-positive and human epidermal growth factor receptor 2-negative (HRþ/ HER2- ) metastatic breast cancer (mBC) patients during the compassionate use program in Spain from February 2015 to November 2017. Patients and methods: Patient data were collected retrospectively from 35 hospitals in Spain. Patients with HRþ/HER2- mBC who had progressed on 4 treatments for advanced disease were eligible. Results: A total of 219 patients received palbociclib in combination with aromatase inhibitors (110; 50.2%), fulvestrant (87; 39.7%), tamoxifen (8; 3.6%) or as single agent (10; 4.6%). Mean age of the patients was 58 years; 31 patients (16.1%) were premenopausal and 162 (83.9%) were postmenopausal at the beginning of treatment with palbociclib. Patients had received a median of 3 previous lines of endocrine therapy (ET) for advanced disease. Real-world tumor response (rwTR) and clinical benefit rate were 5.9% (n ¼ 13) and 46.2% (n ¼ 101), respectively. The median real world progression-free survival (rwPFS) was 6.0 months (95% CI 5.7e7.0) and the median overall survival was 19.0 months (95% CI 16.4e21.7). Subgroup analysis revealed a significant difference in median rwPFS in patients treated with palbociclib plus fulvestrant depending on the duration of prior treatment with fulvestrant monotherapy (>6 versus 6 months; HR 1.93, 95% CI 1.37e2.73, p < 0.001). The most frequently reported toxicities were neutropenia, asthenia, thrombopenia and anemia. Conclusions: Palbociclib can be an effective and safe treatment option in patients with heavily pretreated endocrine-sensitive mBC, especially in those with longer PFS to previous ET.