When compared to prednisone, cabozantinib failed to improve overall survival of heavily pretreated patients with metastatic castration-resistant prostate cancer (mCRPC) who experienced disease progression after docetaxel and abiraterone acetate and/or enzalutamide, according to a study published in the Journal of Clinical Oncology.1
For this phase 3 COMET-1 study, investigators enrolled 1028 patients with progressive mCRPC after receipt of docetaxel and abiraterone and/or enzalutamide. Participants were randomly assigned 2:1 to receive cabozantinib 60 mg orally once daily or prednisone 5 mg orally twice daily.
Median overall survival was 11.0 months with cabozantinib, versus 9.8 months with prednisone (hazard ratio, 0.90; 95% CI, 0.76-1.06; P = .213), suggesting that the primary end point of overall survival was not met.
Researchers found, however, that 42% of patients who received cabozantinib achieved a bone scan response at week 12, versus 3% of those who had prednisone (P < .001). Radiographic progression-free survival favored cabozantinib (hazard ratio, 0.48; 95% CI, 0.40-0.57; P < .001).
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Cabozantinib was associated with improvements in circulating tumor cell (CTC) conversion, bone biomarkers, and incidence of symptomatic skeletal events, but it was not associated with improved serum PSA outcomes.
Seventy-one percent of patients in the cabozantinib arm reported grade 3 to 4 adverse events, compared with 56% in the prednisone arm; 33% and 12% discontinued therapy, respectively.
1. Smith M, De Bono J, Sternberg C, et al. Phase III study of cabozantinib in previously treated metastatic castration-resistant prostate cancer: COMET-1. J Clin Oncol. 2016 Jul 11. doi: 10.1200/JCO.2015.65.5597 [Epub ahead of print]