patients receiving enzalutamide for metastatic castration-resistant prostate cancer: response assessment and imaging biomarkers

and during the treatment. A Cox proportional hazards regression model was used to assess the associations between metabolic parameters and clinical outcomes. Results: Univariate analysis showed no significant correlation between biochemical and FCH-PET responses. Multivariate analysis showed that only baseline maximum standardized uptake value (SUV max ) significantly correlated with biochemical progression-free survival, radiological progression- free survival and overall survival. Conclusion: Our findings suggest that FCH-PET/CT may play a role in defining prognosis of patients receiving enzalutamide because baseline SUV max proved to be an independent prognostic factor. The life expectancy of patients with metastatic castration-resistant prostate cancer (mCRPC) has greatly increased since the introduction of new drugs capable of significantly prolonging survival; however, it is crucial to identify when the disease progresses during the course of one of these treatments in order to be able to change it appropriately. Medical oncologists usually define progressive disease on the basis of the Response Evaluation Criteria in Solid Tumors (RECIST), first published in 2000 (1) and updated in 2009 (RECIST 1.1) (2), or the WHO criteria (3), which are used to assess the objective responses of solid tumors to anti- cancer treatments not only in everyday clinical practice, but also during the development and regulatory approval of new drugs. However, these criteria are substantially based on the systematic assessment of changes in the size of target lesions during treatment, and are clearly less useful in the presence of unmeasurable lesions, particularly bone metastases. Furthermore, they not be able to assess the efficacy of targeted, immunological or hormonal agents, whose cytostatic action leads to low response rates despite their good antitumoral activity (4,5) or a paradoxical increase in tumor size due to tumor necrosis (6). The RECIST and WHO criteria are therefore clearly limited in the case of mCRPC as 80-90% of the patients have bone metastases (7) and many are treated with hormonal agents.