To switch or not to switch? A real-life experience using dexamethasone in combination with abiraterone.

Abstract

The recently published phase II prospective SWITCH trial evaluated whether patients with metastatic castration-resistant prostate cancer (mCRPC) treated with abiraterone acetate could benefit from a ‘steroid switch’ from prednisone to dexamethasone. A total of 26 patients, both chemonaïve (14 patients) or pretreated with docetaxel (12 patients), with biochemical and/or limited radiological progression, were enrolled in this trial. Primary endpoint was prostate specific antigen (PSA) 30 defined as the proportion of patients with a PSA level decline 30% or more after 6 weeks of treatment with abiraterone acetate + dexamethasone. Secondary endpoints were: a PSA50 rate (defined as the proportion of patients with PSA decline of 50% or more after 12 weeks on abiraterone acetate + dexamethasone), biochemical and radiological progression-free survival (bPFS and rPFS, respectively), benefit from subsequent treatment and identification of biomarkers of response. Primary endpoint was reached in 46.2% of patients (12 patients), and two patients had an objective partial response on computed tomography scan. Median bPFS and rPFS were 5.3 months and 11.8 months. We present a case series of 11 patients who were consecutively treated with a steroid switch at our institution from January 2016 to August 2018 to investigate if this strategy could be used in a ‘real-life’ setting. We observed a PSA30 response in two patients (18%), median bPFS was 4.77 months (95% confidence interval [CI] 2.5–14.6) and median rPFS was 7.2 months (95% CI 3.8–15.5). Seven patients had a radiological stable disease as best response to steroid switch. Three patients were being still treated with abiraterone acetate + dexamethasone at data cut-off time. Our case series confirms that switching from prednisone to dexamethasone during abiraterone acetate treatment produces biochemical and radiological responses in both a predocetaxel and a postdocetaxel setting, providing a clinical benefit in mCRPC patients. However, to date, there is no clear indication as to which patient could benefit most from this kind of strategy.