Prediction of Severe Anemia and Neutropenia Induced by Abemaciclib in Patients With Breast Cancer

Background/Aim: Neutropenia and anemia are common and potentially serious adverse events associated with abemaciclib use in breast cancer, but their risk factors remain underexplored. This study aimed to identify the clinical predictors of severe neutropenia and anemia following the initiation of abemaciclib.

Patients and Methods: The medical records of 252 patients with breast cancer who received abemaciclib therapy between August 2011 and November 2024 were retrospectively reviewed. The risk factors for severe neutropenia and anemia were identified based on clinical characteristics and laboratory values. Moreover, the timing of dose reduction after the initiation of abemaciclib treatment was compared with progression-free survival and overall survival using log-rank analysis.

Results: Body mass index (BMI) <22.4 kg/m² and pre-treatment neutrophil count <2,800×10⁶ cells per liter were associated with an increased risk of grade ≥3 neutropenia [odds ratio (OR) (95% confidence interval, CI)=2.1 (1.1-4.0), p=0.03; OR (95%CI)=3.2 (1.5-6.7), p=0.003, respectively]. Also, BMI <22.4 kg/m², hemoglobin level <8.9, and alanine aminotransferase (ALT) ≥60 U/l were significantly associated with an increased risk of grade ≥3 anemia [OR (95%CI)=5.0 (1.1-22.4), p=0.04; OR (95%CI)=1.6 (1.1-2.5), p=0.03; OR (95%CI)=9.6 (1.5-60.1), p=0.02, respectively].

Conclusion: BMI and neutrophil count before treatment were significantly associated with an increased risk of abemaciclib-induced grade ≥3 neutropenia. Moreover, BMI, ALT, and hemoglobin were significantly associated with grade ≥3 anemia following abemaciclib initiation. These factors should be considered in determining individual risk of neutropenia and anemia and risk-benefit ratio of abemaciclib.