Background Abiraterone and enzalutamide are recommended for patients with metastatic castrate-resistant prostate cancer (mCRPC) who are chemotherapy-naive or have received treatment with docetaxel. Clinical practice guidelines do not explain the optimal sequence or combination of these agents. Sequencing decisions of treatment are made depending on the extent and pace of disease, co-morbidities, patient and medical preferences.
Purpose Determine the response in prostate-specific antigen (PSA) levels in mCRPC patients treated with abiraterona or enzalutamida in order to clarify the optimal sequence of treatment.
Material and methods A single-centre, retrospective, observational study. All patients with mCRPC, treated with abiraterone or enzalutamide from January 2012 to August 2017, were included. Dose, treatment duration and starting date were obtained through the electronic prescription program. Age, tumour extension, metastasis, diagnosis date and previous treatments (complete androgen deprivation therapy, radiotherapy, docetaxel and prostatectomy) were also recorded from patient clinical records.
Response to treatment was assessed through PSA testing at the beginning of treatment and at 4, 8 and 24 weeks. The proportion of patients achieving 50% and 90% PSA reduction was calculated for each period. Descriptive statistics were performed with SPSS 20.0.
Results Sixty-seven patients were included. Mean age ±SD =78±7 years, mean Gleason grade was 8, the main metastatic location were bone and regional lymph node. Sixty-two per cent had underwent radical prostatectomy. Mean time from diagnosis to abiraterone and enzalutamide treatment was 6.7 and 4.3 years, respectively. Fifty-one per cent of patients with abiraterone and 87% with enzalutamide were pre-treated with complete androgen deprivation therapy. Radiotherapy was given to 73% of abiraterone patients and 50% to enzalutamide patients. Ten patients received abiraterone before enzalutamide.
The following table shows patients (%) who achieved 50% and 90% PSA reduction at 4, 8 and 24 weeks after treatment initiation, depending on previous therapy.
Treatment with abiraterona needs to be continued at least for 8 weeks in order to obtain significant PSA reductions in most patients.
Abiraterone refractory patients still achieve significant PSA reductions with enzalutamide although they require longer periods of treatment to do so.
ConclusionNo conflict of interest
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