ORIGINAL ARTICLE Prognostic value of 18F–choline PET/CT metabolic parameters in patients with metastatic castration-resistant prostate cancer treated with abiraterone or enzalutamide Paola Caroli 1 & Ugo De Giorgi 2 & Emanuela Scarpi 3 & Lorenzo Fantini 1 & Andrea Moretti 4 & Riccardo Galassi 4 & Monica Celli 1 & Vincenza Conteduca 2 & Lorena Rossi 2 & Emanuela Bianchi 5 & Giovanni Paganelli 1 & Federica Matteucci 1 Received: 10 July 2017 /Accepted: 20 October 2017 # Springer-Verlag GmbH Germany 2017 Abstract Purpose The role of 18F – choline positron emission tomography/computed tomography (FCH-PET/CT) in patients with metastatic castration-resistant prostate cancer (mCRPC) has been firmly established in recent years. We analyzed the prognostic value of functional parameters such as mean stan- dardized uptake volume (SUVmean), maximum standardized uptake volume (SUVmax), metabolic total volume (MTV; the volume of interest consisting of all spatially connected voxels within a fixed threshold of 40% of the SUVmax), and total lesion activity (TLA: the product of MTV and mean standard- ized uptake value) estimated with FCH-PET/CT in mCRPC patients in progression after docetaxel and treated with new antiandrogen receptor therapies, abiraterone or enzalutamide. Methods We retrospectively studied 94 mCRPC patients, mean age 74 years (range 42–90), previously treated with docetaxel who were treated with either abiraterone (n = 52) or enzalutamide (n = 42). An FCH-PET/CT was performed at baseline, and patients were evaluated on a monthly basis for serological PSA response and every 3 months for radiological response. We measured MTV, SUVmean, SUVmax and TLA for each lesion and analyzed the sum of MTV (SMTV), SUVmean (SSUVmean), SUVmax (SSUVmax) and TLA (STLA) values for a maximum of 20 lesions. Univariate anal- ysis was used to correlate these data with PFS and OS. Results We observed a median SMTV of 130 cm 3 , median SSUVmax of 106.5 and a median STLA of 495,070. All of these parameters were significant for PFS and OS in univariate analysis, while only STLA was significant for PFS and OS in multivariate analysis after adjusting for lesion and age (p < 0.0001 and p = 0.001, respectively). Baseline PSA values maintained a certain reliability for OS (p = 0.034). Conclusions Semiquantitative parameters of FCH-PET/CT play a prognostic role in mCRCP patients treated with abiraterone or enzalutamide. Keywords TLA . FCH-PET/CT . Abiraterone . Enzalutamide . CRPC . Castration-resistant prostate cancer Introduction Prostate cancer (PC) remains the leading cancer in North American and European men, with annual age-adjusted inci- dence rates of 85.6 and 59.3 per 100,000, respectively [1]. About 50% of pathologically high-risk patients (those with wide positive margins and/or pT3) and about 10% of low- risk cases (negative margins and pT2) will develop a local relapse within 15 years of surgery [2]. Almost 90% of meta- static PC patients initially respond to castration-induced an- drogen deprivation. However, this therapeutic response has a median duration of 18–24 months, after which the tumor * Paola Caroli paola.caroli@irst.emr.it 1 Nuclear Medicine Unit, Istituto Scientifico Romagnolo per lo Studio e la Cura dei Tumori (IRST) IRCCS, Meldola, Italy 2 Department of Medical Oncology, Istituto Scientifico Romagnolo per lo Studio e la Cura dei Tumori (IRST) IRCCS, Meldola, Italy 3 Unit of Biostatistics and Clinical Trials Unit, Istituto Scientifico Romagnolo per lo Studio e la Cura dei Tumori (IRST) IRCCS, Meldola, Italy 4 Nuclear Medicine Unit, Morgagni Pierantoni Hospital, Forlì, Italy 5 Department of Medical Oncology, Infermi Hospital, Rimini, Italy Eur J Nucl Med Mol Imaging https://doi.org/10.1007/s00259-017-3866-2