Abstract 5103: Characterization of the genomic landscape and actionable mutations in Taiwanese prostate cancer patients
Authors: Tan Kien Thiam , Wu Chia-Ling , Lu Yen-Jung , Tse Ka-Po , Li Chien-Feng L 
Published: June 2022

Background: Prostate Cancer (PCa) is the second most common male cancer worldwide and the most common cancer in males over 65 years old. PCa is the sixth most common cancer in Taiwan, and its incidence rate has increased gradually over the past 30 years. PAPR inhibitors are the only type of targeted drug approved by the FDA to treat advanced castration-resistant prostate cancer (CRPC) that has grown after the hormone therapy drugs. This study aimed to characterize the genomic profile of Taiwanese PCa and explore whether there are potential treatment guidances derived.

Methods: Formalin-fixed paraffin-embedded (FFPE) tumor tissues from 99 patients diagnosed with PCa and collected at Chi-Mei Medical Center (CMMC) were subject to next-generation sequencing using ACTOnco® CGP panel that cover coding regions of 440 cancer-related genes. Genomic alterations (GAs) and signatures, including single nucleotide variations (SNVs), short insertions and deletions (InDels), copy-number variations (CNVs), fusion genes, tumor mutations burden (TMB), and microsatellite instability (MSI) status were retrieved. The gene mutation prevalence was compared with the Western population using the TCGA prostate cancer dataset.

Results: A total of 1558 variants was identified, including 215 SNVs, 22 InDels, 1178 CN gain and 135 homozygous deletions. Similar to the Western population, the most frequently mutated genes were SPOP (21.2%), KMT2C (10.1%), MUC16 (8.1%), TP53 (6.1%), ARID2 (5.1%), IDH1 (5.1%), PTGS2 (5.1%). Further analysis showed that 12 patients harbored deleterious/likely deleterious mutations in genes implicated in homologous recombination (HRR) DNA repair pathway, including three BRCA2, two CDK12, BRAD1 and ARID1A, respectively, and one ATR, ATM and PALB2, respectively. All BRCA2 mutations were predicted to be germline origin and only one-third of 12 HRR mutants had a biallelic gene loss. Median TMB calculated from NGS data is 0.6 muts/Mb (range 0 to 4.5) and all samples are microsatellite-stable (MSS). Therapeutically actionable gene and pathway analysis revealed that up to 24.2% of patients harbored at least one aberration against FDA-approved targeted drugs, such as MET copy number (CN) gain (11.1%), mTOR pathway aberration (6.1%), HRR gene biallelic loss (4%), BRAF activating mutation (4%), IDH1 activating mutations (4%), EGFR CN gain (3.0%), FGFR1 CN gain (2.0%), MET fusion (1.0%) and BRAF fusion (1%).

Conclusion: This CGP study unraveled the genomic profile of Taiwanese prostate cancers, and the results showed that GAs identified could serve as a potential biomarker to guide personalized, targeted therapies in one-fourth of patients.

Citation Format: Kien Thiam Tan, Chia-Ling Wu, Yen-Jung Lu, Ka-Po Tse, Chien-Feng L Li. Characterization of the genomic landscape and actionable mutations in Taiwanese prostate cancer patients [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5103.