Biomarker patterns of localized and metastatic prostate cancer.

Abstract

192 Background: Presence or absence of metastases is a determining factor for prostate cancer prognosis. Common sites of metastasis include bone (B), lymph nodes (LN) or visceral organs (V). We sought to determine theranostic biomarker differences between primary (P) and metastatic (M) specimens, with subset analysis for differences between metastatic sites. Methods: 497 prostate cancer cases referred to Caris Life Sciences between 2009 thru 2014 were evaluated. Specific testing was performed and included a multiplatform approach: sequencing (Sanger, NGS), protein expression (IHC) and gene amplification (CISH/FISH). Results: 58% (287/497) were M specimens, of which 23% (66), 24% (68) and 52% (149) were from B, LN and V, respectively. Significant differences for EGFR amplification/overexpression, low MGMT expression, TOPO1/2A overexpression and higher PTEN mutation rate were found in the M subgroup. These alterations indicate a role for EGFR/PTEN in progression of prostate cancer, and potential role of MAPK/PAM-targeted therapies, alkylating agents and topoisomerase inhibitors in M disease. Mutational profiles of the M subgroup are more genetically unstable exhibiting mutations in 60% of genes tested (notable events include APC & β-Catenin, PTEN, TP53 and BRCA1/2) vs. 30% observed in the P subgroup (p=0.0067). In the subset analysis, EGFR amplification was higher in B (29%) and V (24%) compared to LN (13%); (not significant). Low TS expression was more frequent in B vs. LN (p=0.004), TOPO2A overexpression was higher in V vs. B (p=0.0001) and there was a trend for PD1 positive infiltrating lymphocytes being more abundant in LN vs B (p=0.09). Interestingly, cMET overexpression (7/230) and amplification (1/162) were rarely observed across the cohort, providing support for the surprising failure of cabozantinib in castration-resistant prostate cancer. Conclusions: Our data indicate a role for multiplatform profiling to identify therapeutic options that are appropriate for subsets of patients. Molecular changes associated with M disease including EGFR, PTEN, MGMT and TOPO1/2A, present opportunities for developing therapeutic strategies which may include a combination of targeted therapies, as well as traditional cytotoxic chemotherapies.