Real-world Outcomes of Cyclin-dependent Kinase Inhibitors Continued Beyond First Disease Progression in Hormone Receptor-positive Metastatic Breast Cancer.

BACKGROUND: CDK4/6 inhibitors (CDK4/6i), in combination with aromatase inhibitors, are United States Food and Drug Administration-approved for the treatment of hormone receptor-positive (HR+)/human epidermal growth factor receptor 2-negative (HER2-) metastatic breast cancer (MBC). The effectiveness of continuing them beyond first disease progression (PD) is currently unknown. This retrospective study evaluated the impact of the continuation of CDK4/6i beyond first PD in HR+/HER2- MBC using real-world experience. PATIENTS AND METHODS: A single-institution retrospective review of patients with HR+ MBC who received CDK4/6is from 2015 to 2018 and where CDK4/6is were continued beyond first PD. The primary outcome was progression-free survival (PFS) after initial PD on CDK4/6i therapy. RESULTS: Thirty women with HR+/HER2- MBC met eligibility criteria. Patients were identified from a prospective database of patients at the Cleveland Clinic Foundation who were prescribed CDK4/6is. The median age and follow-up duration were 47.5 years and 27 months, respectively. Most patients received palbociclib (PA)/letrozole as initial therapy (67%), followed by PA/fulvestrant (23%), and PA/other aromatase inhibitor (20%), and abemaciclib with either fulvestrant or letrozole (6%). As of January 31, 2019, 25 (83.3%) patients were still alive, and 19 (63%) patients had progressed. The estimated median PFS for continued CDK4/6i use beyond the first PD was 11.8 months (95% confidence interval, 5.34-13.13 months). CONCLUSIONS: Among a small cohort of patients with HR+ MBC in a non-clinical trial setting, continuation of CDK4/6i-endocrine treatment post initial PD was associated with a median PFS of about 12 months. Formal randomized clinical trials evaluating the continuation of CDK4/6is beyond the first PD are currently ongoing and will provide more answers to this important clinical question.

Phase I trial of weekly docetaxel, weekly doxorubicin, daily oral cyclophosphamide, and G-CSF (ConTAC regimen) in advanced malignancies.

PURPOSE: This was a phase I study evaluating the dose limiting toxicity (DLT) and the maximum tolerated dose (MTD) of weekly docetaxel, doxorubicin and daily oral cyclophosphamide with G-CSF support (ConTAC regimen). PATIENTS AND METHODS: Cohorts of 3-6 patients with advanced breast or other solid malignancies were entered at subsequently higher dose levels until dose-limiting toxicities (DLT) were noted in 2 or more patients per dose level during the first 6 weeks of therapy. This study escalated dosages of docetaxel and doxorubicin simultaneously, while the dose of oral cyclophosphamide was fixed at 60 mg/m(2) daily. RESULTS: Sixteen patients were enrolled. Grade 3-4 adverse events during the first 6 weeks of treatment were neutropenia (n = 1 at dose level #1 and n = 3 at dose level #4), anemia (n = 2 at dose levels 1 and 4), and nausea/vomiting (n = 1 at dose level #4). After 6 weeks of therapy, grade 3-4 toxicities included anemia (n = 3), neutropenia (n = 7), Hand-Foot syndrome (n = 2) and grade 3 cystitis and pneumonia (n = 1 at dose level #4). Five patients with advanced breast cancer and 1 patient with metastatic lung cancer responded to the chemotherapy. CONCLUSIONS: Grade 4 neutropenia was the DLT. The MTD, was established at dose level #3 (doxorubicin at 25 mg/m(2) and docetaxel at 25 mg/m(2) weekly with oral cyclophosphamide dose of 60 mg/m(2) daily). Myelosuppression at that dose level was moderate with G-CSF given concurrently.