Risk Factors and Clinical Significance of Grade ≥3 Neutropenia During the First Cycle of Cabazitaxel Therapy With Primary Pegfilgrastim Prophylaxis in Metastatic Castration-resistant Prostate Cancer.

BACKGROUND/AIM: Cabazitaxel is an established treatment for metastatic castration-resistant prostate cancer (mCRPC) previously treated with a docetaxel-containing regimen; however, it is frequently associated with severe neutropenia. Although primary prophylaxis with pegfilgrastim is widely used, severe neutropenia still occurs. The present study aimed to identify risk factors for grade ≥3 neutropenia during the first cabazitaxel cycle (Cycle 1) under universal pegfilgrastim prophylaxis and to evaluate its clinical significance.

PATIENTS AND

METHODS

This retrospective study analyzed 40 patients with mCRPC treated with cabazitaxel at our institution between January 2015 and January 2025. All patients received primary prophylactic pegfilgrastim on day 3 of each cycle. The primary endpoint was the occurrence of grade ≥3 neutropenia during Cycle 1. A logistic regression analysis was performed to identify associated factors. Overall survival (OS) and progression-free survival (PFS) were analyzed using the Kaplan-Meier method and compared using the Log-rank test.

RESULTS

Grade ≥3 neutropenia during Cycle 1 occurred in 18 patients (45.0%). A univariate analysis identified age ≥75 years and prior docetaxel exposure ≥9 cycles as significant risk factors for grade ≥3 neutropenia. In a multivariate analysis, prior docetaxel exposure ≥9 cycles was identified as an independent predictor. Febrile neutropenia occurred in six patients (15.0%) during Cycle 1. There were no significant differences in OS or PFS between patients with and without grade ≥3 neutropenia.

CONCLUSION

Despite universal pegfilgrastim prophylaxis, severe neutropenia during the first cabazitaxel cycle remains common, particularly in patients with extensive prior docetaxel exposure. However, early grade ≥3 neutropenia was not associated with poorer survival outcomes. These results suggest that under adequate supportive care, early hematologic toxicity alone does not preclude continued cabazitaxel treatment.