Evaluation of a predefined AS threshold in a large cohort of men with localized prostate cancer.

Abstract

36 Background: Men with newly diagnosed, localized prostate cancer (PC) have historically been selected for active surveillance (AS) using clinicopathologic features. However, a clinical cell−cycle risk (CCR) score has been developed to include both molecular [cell cycle progression (CCP) RNA signature] and clinical [Cancer of the Prostate Risk Assessment (CAPRA)] features. Previous validations have demonstrated that this combined CCR score provides improved prognostic information relative to molecular or clinical features alone. As such, a CCR threshold score has been recently developed and validated to identify men with low−risk disease who may be candidates for AS. Here, we have evaluated the performance of the AS threshold in a contemporary cohort of men with newly diagnosed localized PC. Methods: Men with localized adenocarcinoma of the prostate who were treated at the Ochsner Clinic between 2006 and 2011 (4 patients were diagnosed in 2012−2014) were evaluated. Formalin−fixed paraffin embedded biopsy tissue and was analyzed for the RNA expression of 46 genes to obtain a CCP score. The CCR score was calculated as (0.57xCCP) + (0.39xCAPRA). A CCR score threshold of 0.8 has been previously validated in a cohort of conservatively managed men. Men with a CCR score equal to the threshold had an estimated 10−year disease−specific mortality risk of 3.3%, while men with scores below the threshold had a 2.7% risk. Results: Complete molecular and clinical information were available for 767 men with a median clinical follow−up time of 5.6 years measured from date of diagnosis. Overall, 217 men had CCR scores ≤ 0.8. Of these, 125 were treated by radical prostatectomy, 61 with radiation, 2 with radiation with hormones, 2 with hormones only, and 19 with watchful waiting. Treatment for eight men was unknown. One patient (0.5%) with a CCR score below the AS threshold progressed to metastatic disease, and was initially treated with radiation. Conclusions: We evaluated the performance of a previously validated AS threshold on a contemporary US cohort. Although the majority of the patients in this study were treated, the observed metastatic event rate of 0.5% supports that the CCR threshold can be safely used to identify candidates for AS.