Abstract 231P
Background
Cyclin-dependent kinase 4/6 inhibitors (CDK4/6i) currently represent the standard of care for the initial treatment of patients with metastatic hormone receptor-positive/human epidermal growth factor receptor 2-negative (HR+/HER2-) breast cancer. The aim of our study is to evaluate the safety of the use of concomitant radiation therapy (RT) in a consecutive series of HR+/HER2- patients treated in two academic institutions with CDK4/6i in the metastatic setting.
Methods
From September 2017 to February 2020, we collected and analysed a sequential series of patients with metastatic disease treated with CDK4/6i, receiving RT or not, at two European institutions. Primary outcomes of the study were the impact of concomitant RT on any toxicity (any grade), any adverse events (AEs) ≥G3, CDK4/6i dose reduction rate, and CDK4/6i treatment discontinuation rate.
Results
We analysed a total of 133 consecutive patients. The median age of the patients was 59 years (range 37-86). Concomitant RT administration was not significantly related to higher AEs ≥G3 (p=0.45) and any grade toxicity (p=0.69); there was no association with RT and CDK4/6i dose reductions (p=1.0) and discontinuations (p=0.07). At a median duration of follow-up of 18.8 months, the progression-free survival (PFS) rate was 65.0% and the overall survival (OS) rate was 38.7% in the whole group. The use of concomitant RT did not affect both PFS (p=0.71) and OS rates (p=0.55).
Conclusions
Our data are encouraging regarding the safety of this combination, showing that concurrent RT did not have an impact on systemic treatment conduction and did not increase toxicity.
Clinical trial identification
Editorial acknowledgement
Legal entity responsible for the study
University of Florence.
Funding
Has not received any funding.
Disclosure
All authors have declared no conflicts of interest.