Endothelin-A receptor antagonists in prostate cancer treatment-a meta-analysis

Prostate cancer remains the second leading cause of cancer death in men due to inefficiency of androgen deprivation therapy or androgen blockade. Endothelins (ETs) and the two endothelin receptor family members A and B (ETA and ETB) are known to play important roles in the progression of many malignancies, including prostate cancer. However, phase III clinical studies did not reach a unanimous conclusion regarding ETA receptor antagonists in prostate cancer treatment. Here, we provide a meta-analysis of clinical studies using ETA receptor antagonists to treat prostate cancer, especially the hormone refractory prostate cancer (HRPC). Data were extracted from nine studies that used Zibotentan or Atrasentan, two selective ETA receptor antagonists, to treat prostate cancer and meet the selection criteria. The results indicated that the overall survival (OS) and the progression-free survival (PFS) of patients treated with Zibotentan did not show significant difference with the patients treated with placebo (pooled hazard ratio (HR) for OS, 0.86, 95% CI 0.70-1.06; pooled HR for PFS, 0.98, 95% CI 0.91-1.06). No statistically significant difference was detected either as to the OS and PFS of patients between the Atrasentan treated group and the group treated with placebo (pooled HR for OS, 0.99, 95% CI 0.90-1.08; pooled HR for PFS, 0.94, 95% CI 0.86-1.02). Notably, the level of prostate-specific antigen (PSA) and the incidence of bone pain were significantly lower in the Atrasentan treated patients compared to the controls (pooled HR for time of PSA progression, 0.87, 95% CI 0.78-0.97; and pooled relative risk (RR) for bone pain, 0.68, 95% CI 0.48-0.97). In addition, increasing of PSA and bone alkaline phosphatase (BALP) were significantly delayed with Atrasentan treatment (P<0.05). Together, these data suggest that Atrasentan has an effect on cancer-related bone pain and skeletal-events in patients with prostate cancer.