It is not clear which agent should be used in the treatment of metastatic castration-resistant chemotherapy-naive patients. Many options have been evaluated until today; docetaxel has become prominent as treatment of choice for chemotherapy, while abiraterone and enzalutamide have become the hormonal treatments of choice. There is no prospective study on these agents; therefore, the treatment of these patients is up to the clinicians’ decision.
When we examined the studies of these agents in CRPC patients, in a Phase 3 randomized study where docetaxel, which was the first agent used, was compared with mitoxantrone, median survival in patients who received docetaxel was found to be 18.9 months (4). In a study on abiraterone in this population, median survival was 34.7 months (17). In another study on enzalutamide in CRPC patients, overall survival was found to be 35.3 months (21).
In the present study, the overall survival of docetaxel was 18.66 months, and it was 16.26 months for abiraterone and enzalutamide which are hormonal therapies. In the numerical analysis of the results, the survival of the patients in the docetaxel arm was almost the same as the that of the pivotal study (4). However, this was not the case for the patients taking enzalutamide and abiraterone. The overall survival of these agents with an overall survival of 34 months in their pivotal study, was 16.26 months in the present study. This may be due to the difference in the selection of patients. In pivotal studies of these agents, asymptomatic patients were especially included. As there was no such selection criteria in our study, it may have resulted in the difference. In Turkey where the present study was conducted, abiraterone or enzalutamide can be used in patients who are not suitable for chemotherapy. Therefore, patients whose general condition is relatively worse receive hormonal therapies. The age parameter was significantly in favor of hormonal therapies and this result also promotes the condition. Overall survival may be low in our study due to this disadvantage in patient selection. Poor survival in the pivotal study of docetaxel may result from not using other agents, which prolong life time, in sequential therapy.
In our study, progression-free survival was statistically significantly higher in the hormonal therapy arm than the group receiving chemotherapy. Despite the above-mentioned disadvantage in the selection of the patients, hormonal therapies were successful in progression-free survival compared to chemotherapy; however, the difference did not reflect on overall survival. This success in progression-free survival, on the other hand, obtained despite the limited number of patients. Therefore, based on the results of our study, hormonal therapies (abiraterone or enzalutamide) are more successful than docetaxel in castration-resistant metastatic chemotherapy-naive patients. Nevertheless, it is not possible to reach a definite conclusion based on the results of our retrospective study and larger prospective randomized controlled studies are needed on this subject.