Abstract C149: Next-generation sequencing of biopsy-free circulating tumor DNA revealed frequent actionable alterations in advanced hepatocellular carcinoma
Authors: Ikeda Sadakatsu , Banks Kimberly , Lanman Richard B. , Kurzrock Razelle 
Published: May 2016

Background: Treatment options for advanced hepatocellular carcinoma (HCC) are limited. Tumor biopsy is not routinely performed in HCC and involves risks. As such, genomic analysis of HCC specimens for matched-targeted therapies is not often an option. The utility of cell-free circulating tumor DNA (ctDNA) next-generation sequencing (NGS) to identify somatic alterations and target therapy in HCC patients has not yet been characterized.

Methods: We prospectively evaluated 14 patients with advanced hepatocellular carcinoma (January 2015 - June 2015) using a ctDNA NGS panel of 68 genes (Guardant360). The test sequences complete exons for single nucleotide variants (SNVs) in 68 genes, amplifications of 16 genes, fusion events in ALK/RET/ROS1/NTRK1, and specific insertion/deletion mutations. The mutant allele fraction for detected alterations is calculated relative to wild type in cell-free DNA. The test is sensitive to a single fragment of mutated ctDNA in a 10 ml blood sample, and analytic specificity is &gt;99.9999%. All patients signed informed consent. When appropriate, patients were presented at the UCSD Moores Cancer Center Molecular Tumor Board.

Results: All patients (100%) had somatic alterations (SNVs and/or amplifications) (average = 3.6 alterations per patient [range, 1-8]) with a median mutant allele fraction of 0.29% (range 0.1% - 37.77%). Point mutations were identified in the following genes: TP53 (N = 8 patients), CTNNB1 (4), PTEN (1), CDKN2A (1), ARID1A (1), and MET (1); amplifications were identified in CDK6 (2), EGFR (2), MYC (2), BRAF (1), RAF1 (1), FGFR1 (1), CCNE1 (1), PIK3CA (1), and ERBB2/HER2 (1). Eleven patients (79%) had at least one actionable alteration identified. The patient with a CDKN2A inactivating mutation and a CTNNB1 activating mutation was treated with palbociclib (CDK4/6 inhibitor) and celecoxib (COX-2/Wnt inhibitor); des gamma-carboxy prothrombin level decreased by 84% over 2 months (1410 to 242 ng/ml [normal: 0.0 - 7.4 ng/ml]) (alpha fetoprotein (AFP) low at baseline). Another patient with a PTEN inactivating mutation and a MET activating mutation received sirolimus (mTOR inhibitor) and cabozantinib (MET inhibitor); AFP declined by 63% in one month (8320 ng/ml to 3045 ng/ml [normal: 0-15 ng/ml]). (Imaging studies are pending).

Conclusion: ctDNA profiling is feasible in advanced HCC, and may provide a tissue biopsy-free alternative in these difficult-to-biopsy patients. Two patients who received matched-targeted therapy demonstrated rapid biomarker response. Further study of clinical validity and utility is ongoing.

Citation Format: Sadakatsu Ikeda, Kimberly Banks, Richard B. Lanman, Razelle Kurzrock. Next-generation sequencing of biopsy-free circulating tumor DNA revealed frequent actionable alterations in advanced hepatocellular carcinoma. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2015 Nov 5-9; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl 2):Abstract nr C149.