2151 - Clinical outcome and toxicity data in patients with advanced breast cancer treated with cyclin-dependent kinase 4/6 (CDK4/6) inhibitors combined with endocrine therapy in a real-world clinical setting.

Background

Clinical trials evaluating treatment with cyclin-dependent kinase 4/6 inhibitors (CDK4/6i) in combination with aromatase inhibitors (AI) or fulvestrant have shown promising clinical benefit in patients with advanced breast cancer. We evaluated real-world clinical outcomes and toxicity rates in patients with advanced breast cancer who received treatment with CDK4/6i in routine clinical practice.

Methods

We retrospectively reviewed medical records of patients with advanced hormone receptor (HR)-positive, human epidermal growth factor receptor 2 (HER2)-negative breast cancer treated at Departments of Oncology-affiliated with the Hellenic Cooperative Oncology Group (HeCOG). All patients received hormonal therapy in combination with CDK4/6i as first-, second- or third-line of treatment and beyond. The primary end point was progression-free survival (PFS).

Results

From 07/2015 to 03/2019, 191 women were treated with CDK4/6i combined with endocrine therapy (median age: 52.2 years, postmenopausal 87, 45.5%); 86 (45%) patients received CDK4/6i in combination with AI and 105 (55%) with fulvestrant. CDK4/6i were administered as first-line treatment in 65 (34%) patients, second-line treatment in 39 (20.4%) and third-line and beyond in 83 (43.5%) patients. The median follow-up was 54.3 months (95%CI 43.0-61.2). The median PFS for patients who received first-line treatment was 18.7 months, second-line treatment 11.5 months and ≥3 lines of treatment 7.5 months. The median overall survival since the initiation of CDK4-6i treatment was 23.2 months (95% CI 20.4-30.3). The most common adverse events were neutropenia (100 patients, 52.4%) and fatigue (24, 12.6%). Grade 3-4 adverse events occurred in 55 (28.8%) patients, while 2 (1.0%) patients permanently discontinued treatment due to toxicity.

Conclusions

Among patients with HR-positive advanced breast cancer treated with CDK4/6i combined with endocrine, the estimated PFS was comparable to previously reported data. Treatment was well tolerated, with a low drug discontinuation rate.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

Hellenic Cooperative Oncology Group.

Funding

Hellenic Cooperative Oncology Group (HeCOG).

Disclosure

E. Fountzilas: Travel / Accommodation / Expenses: K.A.M ONCOLOGY / HEMATOLOGY; Travel / Accommodation / Expenses: Merck; Shareholder / Stockholder / Stock options: Deciphera. G. Aravantinos: Advisory / Consultancy: Novartis; Advisory / Consultancy: Bristol-Myers Squibb; Advisory / Consultancy: Roche Hellas; Advisory / Consultancy: AstraZeneca; Advisory / Consultancy: Sanofi; Advisory / Consultancy: Amgen; Advisory / Consultancy: Genesis Pharma; Advisory / Consultancy: Merck; Advisory / Consultancy: Pfizer. G. Fountzilas: Advisory / Consultancy: Pfizer; Advisory / Consultancy: Sanofi; Advisory / Consultancy: Roche; Honoraria (self): AstraZeneca. E. Razis: Honoraria (self), Advisory / Consultancy: Novartis; Travel / Accommodation / Expenses: Genesis Pharmaceuticals; Travel / Accommodation / Expenses: Pfizer; Travel / Accommodation / Expenses: Roche; Travel / Accommodation / Expenses: , Bristol-Myers Squibb; Travel / Accommodation / Expenses: Genekor. All other authors have declared no conflicts of interest.