Impact of pegfilgrastim as primary prophylaxis for metastatic castration-resistant prostate cancer patients undergoing cabazitaxel treatment: An open-label study in Japan

Background: Cabazitaxel is an efficacious treatment for patients with metastatic castration-resistant prostate cancer who have previously progressed on docetaxel, but febrile neutropenia during the first cycle is a frequent complication. Asian patients are at increased risk of febrile neutropenia. Although primary prophylaxis with granulocyte colony-stimulating factor can reduce the incidence, its efficacy has not been prospectively demonstrated in Japanese patients with cabazitaxel treatment. Methods: PEGAZUS, a prospective, single-arm study conducted at eight clinical sites in Japan, enrolled 21 heavily pretreated patients with metastatic castration-resistant prostate cancer. Patients received cabazitaxel 25 mg/m² every 3 weeks, up to 10 cycles. Oral prednisolone 10 mg was taken daily. Pegfilgrastim 3.6 mg was administered at least 24 h after the cabazitaxel infusion. The primary endpoint was the incidence of febrile neutropenia in the first cycle. Results: The median number of treatment cycles was seven. The relative dose intensity of cabazitaxel was 67.4% (range, 53.2–91.3%). Two of 21 patients (9.5%) experienced febrile neutropenia in the first cycle. This rate was lower than the rate (43%) previously observed without prophylactic granulocyte colony-stimulating factor in a similar patient population. Six patients showed a prostate-specific antigen response (28.6%). Three of four patients evaluable for tumor response had stable disease and one had progressive disease. Grade ≥3 diarrhea was not observed. Primary prophylaxis with granulocyte colony-stimulating factor significantly reduced the incidence of febrile neutropenia in this study. Conclusions: Cabazitaxel plus granulocyte colony-stimulating factor is safe and effective for Japanese patients with metastatic castration-resistant prostate cancer who have previously progressed on docetaxel.