In a phase II trial reported in the Journal of Clinical Oncology, Slovin et al found that concomitant abiraterone acetate plus prednisone (AAP) and cabazitaxel appeared to produce better outcomes than AAP followed by cabazitaxel upon disease progression in patients with metastatic castration-resistant prostate cancer.
Study Details
In the U.S. multicenter trial, 81 patients were randomly assigned between August 2014 and March 2019 to receive AAP with a switch to cabazitaxel upon radiographic disease progression (n = 42) or concomitant AAP plus cabazitaxel (n = 39).
Key Findings
In the AAP group, median radiographic progression–free survival was 6.4 months (95% confidence interval [CI] = 3.8–10.6 months), and median overall survival was 18.3 months (95% CI = 14.4–37.6 months). At least a 50% decline in prostate-specific antigen (PSA) value was observed in 56% of patients. Patients who switched to cabazitaxel after disease progression exhibited a median second radiographic progression–free survival of 5.4 months (95% CI = 2.8–8.8 months).
In the AAP-plus-cabazitaxel group, median radiographic progression–free survival was 14.8 months (95% CI = 10.6–16.4 months), and median overall survival was 24.5 months (95% CI = 20.4-35.0 months). At least a 50% decline in PSA value was observed in 92.1% of patients. Exploratory assessments of RB expression in pretherapy tumor biopsy, circulating tumor cells, and tissue explants showed no correlation with a preferential benefit from AAP plus concomitant cabazitaxel.
No unexpected toxicities were observed. Grade ≥ 3 adverse events occurred in 64.3% of the AAP group and 60.5% of the AAP-plus-cabazitaxel group. No treatment-related deaths were observed.
The investigators concluded: “AAP [plus cabazitaxel] was safe with improved [radiographic progression–free survival], [overall survival] duration, and a higher proportion of PSA declines. This suggests that AAP [plus cabazitaxel] given earlier rather than sequentially may benefit some men. Further work is needed to identify this population.”
Susan F. Slovin, MD, PhD, FACP, of the Sidney Kimmel Center for Prostate and Urologic Cancers, Memorial Sloan Kettering Cancer Center, is the corresponding author of the Journal of Clinical Oncology article.
Disclosure: The study was supported by Sanofi-Aventis and the Prostate Cancer Foundation. For full disclosures of the study authors, visit ascopubs.org.
