The prostate clinical outlook (PCO) classifier for predicting biochemical recurrences in patients treated by stereotactic body radiation therapy.

Abstract

e16552 Background: Although prostate cancer risk classifiers have been developed for predicting surgical and radiation therapy outcomes, a classifier suitable for predicting biochemical recurrence (BCR) in patients undergoing stereotactic body radiation therapy (SBRT) remains to be defined. SBRT is delivered in large fractions of highly conformal radiation therapy and such treatments are believed to be radiobiologically more effective in treating prostate cancers. The aim of this study is to develop a new classifier specifically for informing patients electing to undergo prostate cancer treatment with SBRT. Methods: We have studied outcomes of 809 patients treated with SBRT between August 2007 and November 2016 at MedStar-Georgetown University Hospital. A Cox regression to BCR was performed and the Prostate Clinical Outlook (PCO) score was calculated at diagnosis based on age at diagnosis, clinical-radiological staging, pre-treatment PSA and Gleason score. Accuracy of the PCO classifier was assessed with concordance (c)-indexes. The results were also compared to classifications by D’Amico and National Comprehensive Cancer Network (NCCN) recurrence risk groups. Results: PCO total scores range from zero to 156 points. The PCO classifier splits patients into 3 risk-groups with the following 5-year BCR-free survival: for low-risk 98%; for intermediate-risk 95%; for high-risk 86%. Our classifier outperforms D’Amico and NCCN for all of the evaluated end-points, with concordance indices of 74 % versus 64 % and 66%, respectively. Conclusions: The PCO classifier is a potential tool for employing readily available parameters to stratify prostate cancer patients and to predict probabilities of BCR after SBRT.