Can prednisone be replaced with dexamethasone in patients with prostate cancer treated with abiraterone acetate?

This study aimed to investigate the use of dexamethasone, instead of prednisone, used with abiraterone acetate (Zytiga) for patients with metastatic castration-resistant prostate cancer (mCRPC). This study found that prednisone to dexamethasone switch can benefit some patients with mCRPC.

Androgen deprivation therapy (ADT) is a treatment used for prostate cancer. It is used to decrease the levels of male sex hormones in the body, including testosterone. Metastatic castration-resistant prostate cancer (mCRPC) is a cancer that has spread outside the prostate gland and keeps growing even when the amount of testosterone in the body is reduced to very low levels. Abiraterone acetate (AA) is a type of ADT. It can be taken with steroids, usually with prednisone. Dexamethasone is another steroid that can be used. The efficacy of dexamethasone along with AA in patients with mCRPC is unclear.

This study included 26 patients with mCRPC. All patients had cancer progression (growth of cancer) under treatment with AA and prednisone. Prednisone was then changed to dexamethasone in all patients. Treatment response was measured through prostate-specific antigen (PSA; a chemical in the blood made by the prostate) levels. 

After at least 6 weeks of treatment, 46.2% of patients had 30% lower PSA levels. After 1 year of treatment, 34.6% of patients had their PSA levels lowered by 50% than at the beginning of the study.

The average progression-free survival (PFS; the time patients were alive without cancer growing) after dexamethasone switch was 11.8 months. The average overall survival after the switch was 20.9 months. 

31% of patients reported mild side effects to dexamethasone treatment. The most common included muscle weakness (12%), high blood pressure (8%) and high blood sugar (8%).

This study found that some patients with mCRPC treated with abiraterone acetate can benefit from a steroid switch from prednisone to dexamethasone.

This trial included a very small number of patients. Larger studies are needed to confirm these findings.