Évaluation de la réponse métabolique en TEP/TDM à la F18-FCH après un mois de traitement par acétate d’abiratérone chez les patients présentant un cancer de la prostate métastatique résistant à la castration

Introduction. - Evolution of prostate cancer to a metastatic castrate-resistance prostate cancer (mCRPC) stage with predominant bone and lymph nodes metastases is of poor prognosis. Abiraterone acetate (AA) has recently been approved in mCRPC treatment after progression on docetaxel chemotherapy with an improvement in overall survival (OS). PSA levels (ng/mL) and performance status are the current standards for the follow up and the treatment response assessment for those patients. 18F-choline PET/CT showed interesting results for the assessment of the metastatic disease and the detection of relapse after a curative treatment with a rising PSA. Our study aimed to show the role of 18F-choline in the early response assessment of AA treatment in mCRPC patients. Another aim to this study was to observe the heterogeneity of the response in patients with various metastatic sites.Material and methods. - Thirty-eight patients with mCRPC were included in a multicentre clinical trial assessing the efficacy of AA with PSA measurements (M0, M1 and M3) and two 18F-choline PET/CT exams: the first one the week before the beginning of the AA treatment M0 and the second one after one month of treatment M1 to assess the metabolic response. The metabolic response was assessed according to modified PERCIST criteria with SUVpeak and SUVmax measurements; the global metabolic response was assessed for all the patients included and for each metastatic site for patients presenting both bone and lymph nodes metastases. The metabolic response was compared to PSA levels measurements and overall survival data Patients were classified in 2 groups: "metabolic responders" if the SUV values showed a reduction of at least 30% compared to the M0 18F-choline PET/CT and "non-metabolic responders" if otherwise. The same classification was done according to each tumoral site for the patients presenting both bone and lymph nodes metastases at M0.Results. - Twenty-nine patients had an 18F-choline PET/CT at M0 and M1 and were classified as follow: 12 patients were "metabolic responders" and 17 patients were "non-metabolic responders" according to the global metabolic evolution. The global metabolic evolution was heterogeneous in 55% of the patients, mostly in "metabolic responders" patients (11 out 12 patients). The decrease in PSA levels was more important but not significant in "metabolic responders" patients; no gain in OS was shown for "metabolic responders". When we analysed the metabolic response in patients presenting multiple metastatic sites: decrease in PSA levels and an advantage in overall survival appeared to be more frequent for patients with a lymph node metabolic response alone or associated with a bone metabolic response, but those results were not significant.Conclusion. - This study showed the utility of 18F-choline PET/CT for the early response assessment of an abiraterone acetate treatment in mCRPC patients. We also showed the heterogeneity of the metabolic response in patients with multiple metastatic sites. (C) 2015 Published by Elsevier Masson SAS.