<?xml version='1.0' encoding='UTF-8'?><xml><records><record><source-app name="HighWire" version="7.x">Drupal-HighWire</source-app><ref-type name="Journal Article">17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">SATO, RYO</style></author><author><style face="normal" font="default" size="100%">YOSHIMI, YUKIHIRO</style></author><author><style face="normal" font="default" size="100%">NISHIO, TETSUHARU</style></author><author><style face="normal" font="default" size="100%">MATSUNAGA, YU</style></author><author><style face="normal" font="default" size="100%">MATSUMOTO, RIKIYA</style></author></authors><secondary-authors></secondary-authors></contributors><titles><title><style face="normal" font="default" size="100%">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</style></title><secondary-title><style face="normal" font="default" size="100%">In Vivo</style></secondary-title></titles><dates><year><style  face="normal" font="default" size="100%">2026</style></year><pub-dates><date><style  face="normal" font="default" size="100%">2026-05-01 00:00:00</style></date></pub-dates></dates><pages><style  face="normal" font="default" size="100%">1628-1636</style></pages><doi><style  face="normal" font="default" size="100%">10.21873/invivo.14313</style></doi><volume><style face="normal" font="default" size="100%">40</style></volume><issue><style face="normal" font="default" size="100%">3</style></issue><abstract><style  face="normal" font="default" size="100%">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.</style></abstract></record></records></xml>