Circulating tumor DNA-targeted sequencing to reveal germline and somatic alterations that can guide decision-making in metastatic castration-resistant prostate cancer.

Abstract

173 Background: The genomic landscape of metastatic castration-resistant prostate cancer (mCRPC) is dynamic with the application of multiple treatments. The circulating tumor DNA(ctDNA), which reveals germline and somatic alterations, provides a mini-invasive tool for monitoring tumor evolution. Methods: We performed an exploratory analysis of 299 ctDNA samples from 8 centers through application of multiple-gene deep targeted sequencing. Results: The most common recurrent genomic alterations were in AR(34.7%), TP53(18.9%), CDK12(15.4%), BRCA2(13.3%), and the majority of these clinically actionable gene alterations were identified in somatic level(CDK12 100% in somatic). The results showed the frequency of AR amplification and TP53 defect significantly increased in post-second and later line treatment group compared with treatment-naive group. AR amplification and TP53 or RB1 defect were associated with resistance to abiraterone or docetaxel. CDK12 was more frequently altered in our cohort than those in previous reports which mainly focused on Caucasian population. The patients with CDK12 defect showed rapid resistance to abiraterone and limited efficacy of PARPi. However, these patients seemed to benefit from chemotherapy, espeacially platnium-based chemotherapy. Conclusions: This multi-institutional real-world study explored the genomic landscape and captured the significant diversity of mCRPC at different treatment stages by liquid biopsy. These findings established genomic drivers associated with resistance to multiple treatments (including PARPi and platinum-based chemotherapy) in mCRPC. Hence, ctDNA targeted sequencing can help guide clinical decision making in mCRPC throughout the whole treatment process. CDK12 might be able to be a novel predictive biomarker to guide treatment selection in mCRPC.