Beyond D'Amico risk classes for predicting recurrence after external beam radiotherapy for prostate cancer: the Candiolo classifier.

BACKGROUND - The aim of this work is to develop an algorithm to predict recurrence in prostate cancer patients treated with radical radiotherapy, getting up to a prognostic power higher than traditional D'Amico risk classification.

METHODS - Two thousand four hundred ninety-three men belonging to the EUREKA-2 retrospective multi-centric database on prostate cancer and treated with external-beam radiotherapy as primary treatment comprised the study population. A Cox regression time to PSA failure analysis was performed in univariate and multivariate settings, evaluating the predictive ability of age, pre-treatment PSA, clinical-radiological staging, Gleason score and percentage of positive cores at biopsy (%PC). The accuracy of this model was checked with bootstrapping statistics. Subgroups for all the variables' combinations were combined to classify patients into five different "Candiolo" risk-classes for biochemical Progression Free Survival (bPFS); thereafter, they were also applied to clinical PFS (cPFS), systemic PFS (sPFS) and Prostate Cancer Specific Survival (PCSS), and compared to D'Amico risk grouping performances.

RESULTS - The Candiolo classifier splits patients in 5 risk-groups with the following 10-years bPFS, cPFS, sPFS and PCSS: for very-low-risk 90 %, 94 %, 100 % and 100 %; for low-risk 74 %, 88 %, 94 % and 98 %; for intermediate-risk 60 %, 82 %, 91 % and 92 %; for high-risk 43 %, 55 %, 80 % and 89 % and for very-high-risk 14 %, 38 %, 56 % and 70 %. Our classifier outperforms D'Amico risk classes for all the end-points evaluated, with concordance indexes of 71.5 %, 75.5 %, 80 % and 80.5 % versus 63 %, 65.5 %, 69.5 % and 69 %, respectively.

CONCLUSIONS - Our classification tool, combining five clinical and easily available parameters, seems to better stratify patients in predicting prostate cancer recurrence after radiotherapy compared to the traditional D'Amico risk classes.

Radiation oncology (London, England). 2016 Feb 24*** epublish ***

Domenico Gabriele, Barbara A Jereczek-Fossa, Marco Krengli, Elisabetta Garibaldi, Maria Tessa, Gregorio Moro, Giuseppe Girelli, Pietro Gabriele, EUREKA-2 consortium

Neuroscience Department, Human Physiology Section, University of Torino, corso Raffaello 30, 10125, Torino, Italy. Division of Radiation Oncology, European Institute of Oncology, and University of Milan, Milan, Italy.  Division of Radiation Oncology, Maggiore University Hospital of Novara, Novara, Italy. Division of Radiation Oncology, FPO-IRCCS Cancer Center of Candiolo (Torino), Candiolo, Italy.  Division of Radiation Oncology, Cardinal Massaia Hospital, Asti, Italy. Division of Radiation Oncology, degli infermi Hospital, Biella, Italy. Division of Radiation Oncology, Civile Hospital, Ivrea, Italy. Division of Radiation Oncology, FPO-IRCCS Cancer Center of Candiolo (Torino), Candiolo, Italy.