Predictors of long-term response to abiraterone in patients with metastastic castration-resistant prostate cancer: a retrospective cohort study

// Elena Verzoni 1 , Ugo De Giorgi 2 , Lisa Derosa 3 , Orazio Caffo 4 , Francesco Boccardo 5 , Gaetano Facchini 6 , Luca Porcu 7 , Fabio De Vincenzo 8 , Alberto Zaniboni 9 , Vincenzo Emanuele Chiuri 10 , Lucia Fratino 11 , Daniele Santini 12 , Vincenzo Adamo 13 , Rocco De Vivo 14 , Angelo Dinota 15 , Caterina Messina 16 , Riccardo Ricotta 17 , Claudia Caserta 18 , Claudio Scavelli 19 , Marina Susi 20 , Alfredo Tartarone 21 , Giuseppe Surace 22 , Alessandra Mosca 23 , Michele Bruno 24 , Sandro Barni 25 , Paolo Grassi 1 , Giuseppe Procopio 1 1 Unit of Medical Oncology 1, Fondazione IRCCS Istituto Nazionale Tumori, Milan, Italy 2 Department of Medical Oncology, IRST, IRCCS, Meldola, Italy 3 Unit of Medical Oncology 2, Istituto Toscano Tumori, Pisa, Italy 4 Ospedale Santa Chiara, Trento, Italy 5 IRCCS AOU San Martino IST and University of Genoa, Italy 6 Unit of Medical Oncology, Department of Uro-Gynecological Oncology, Istituto Nazionale Tumori, Fondazione G. Pascale IRCCS, Naples, Italy 7 Department of Oncology, IRCCS- Istituto di Ricerche Farmacologiche Mario Negri, Milan, Italy 8 Istituto Clinico Humanitas, Rozzano, Italy 9 Fondazione Poliambulanza, Brescia, Italy 10 Ospedale Vito Fazzi, Lecce, Italy 11 Istituto Nazionale Tumori CRO, Aviano, Italy 12 Policlinico Universitario Campus Biomedico, Roma, Italy 13 Medical Oncology Unit, AO Papardo, Messina, Italy 14 Ospedale San Bortolo, Vicenza, Italy 15 Ospedale San Carlo, Potenza, Italy 16 Azienda Ospedaliera Papa Giovanni XXIII, Bergamo, Italy 17 Niguarda Cancer Center, Ospedale Niguarda Ca’ Granda, Milan, Italy 18 AO Santa Maria, Terni, Italy 19 Ospedale S. Cuore di Gesù, Gallipoli, Italy 20 Ospedale Madonna delle Grazie, Matera, Italy 21 IRCCS Centro di Riferimento Oncologico della Basilicata (CROB), Rionero in Vulture, Italy 22 Ospedale D. Camberlingo, Francavilla Fontana, Italy 23 AOU Maggiore della Carità, Novara, Italy 24 PO San G. Moscati, ASL Taranto, Italy 25 AO Treviglio, Italy Correspondence to: Giuseppe Procopio, e-mail: giuseppe.procopio@istitutotumori.mi.it Keywords: abiraterone acetate, castration-resistant, predictive factors, prostate cancer, retrospective studies Received: February 28, 2016 Accepted: April 10, 2016 Published: May 19, 2016 ABSTRACT We aimed to identify clinical predictors of long-term response to abiraterone (defined as >12 months drug exposure) in a retrospective cohort of metastatic castration-resistant prostate cancer patients treated in post-docetaxel setting at 24 Italian centers. The Cox proportional hazards model was used to analyze the association between clinical features and the duration of drug exposure. Results were expressed as hazard ratios (HR) with associated 95% confidence intervals (CI). A total of 143 patients met the inclusion criteria. Their median age was 73 years, median Gleason score 8 and median abiraterone exposure 20 months. At the univariate analysis, a significant correlation with the duration of abiraterone exposure was found for Gleason score (HR 0.82, 95% CI 0.71-0.96; p=0.012), PSA (HR 1.10, 95% CI 1.03-1.18; p=0.08) and lactic dehydrogenase levels (HR 1.22, 95% CI 1.02-1.46; p=0.027), while the association between lower alkaline phosphatase levels and treatment duration was marginally significant (HR 1.07, 95% CI 0.99-1.16; p=0.074). Only PSA and Gleason score were predictive of long-term treatment duration in the multivariate analysis. No other clinical factors resulted to be predictive of sustained response to abiraterone, including metastatic disease at diagnosis and visceral disease, suggesting that all subgroups of patients may derive a substantial clinical benefit from abiraterone treatment. These findings need to be validated in prospective, larger studies.