Abstract 4272: A novel approach to differentiation of somatic vs. germline variants in liquid biopsies using a betabinomial model

Changes in Mutations of Cell-Free DNA and Liver Tumor Tissue in Patients with Advanced Hepatocellular Carcinoma before and after Introduction of Lenvatinib

INTRODUCTION

Cell-free DNA (cfDNA) is expected to contribute to the decision for treatment and prediction of effects with minimally invasion. We investigated the correlation between gene mutations before and after lenvatinib (LEN) treatment and its effectiveness, in order to find advanced hepatocellular carcinoma (HCC) patients who would benefit greatly from the therapy.

METHODS

We analyzed cfDNA before and 6-8 weeks after the start of treatment in 20 advanced HCC patients who started LEN. A next-generation sequencer was used for CTNNB1 and TP53. Concerning TERT promoter, -124C>T and -146C>T mutations are researched using digital PCR. In addition, we examined liver tumor biopsy tissues by the same method. Computerized tomography evaluation was performed at 6-8 weeks and 3-4 months to assess the efficacy.

RESULTS

Frequencies of TERT promoter, CTNNB1, and TP53 mutations in pretreatment cfDNA were 45%, 65%, and 65%, but 53%, 41%, and 47% in HCC tissues, respectively. There were no clear correlations between these gene mutations and the disease-suppressing effect or progression-free survival. Overall, there were many cases showing a decrease in mutations after LEN treatment. Integrating the reduction of CTNNB1 and TP53 genetic mutations increased the potential for disease suppression.

CONCLUSION

This study suggests that analysis of cfDNA in advanced HCC patients may be useful for identifying LEN responders and determining therapeutic efficacy. Furthermore, it has potential for selecting responders for other molecular-targeted drugs.

Phase II trial of niraparib for BRCA-mutated biliary tract, pancreatic and other gastrointestinal cancers: NIR-B

Due to the widespread use of cancer genetic testing in gastrointestinal cancer, the BRCA1/2 genetic mutation has been identified in biliary tract cancer as well as pancreatic cancer. Niraparib is a poly(ADP-ribose) polymerase (PARP) inhibitor, and PARP inhibitors exert their cytotoxicity against cancer cells in the context of homologous recombination deficiency, such as BRCA mutations, via the mechanism of synthetic lethality. The aim of this phase II NIR-B trial is to evaluate the efficacy and safety of niraparib for patients with unresectable advanced or recurrent biliary tract cancer, pancreatic cancer or other gastrointestinal cancers with germline or somatic BRCA1/2 mutations revealed by genetic testing. The primary end point is an investigator-assessed objective response rate in each cohort.Clinical Trial Registration: jRCT2011200023 (ClinicalTrials.gov).

Potential pathogenic germline variant reporting from tumor comprehensive genomic profiling complements classic approaches to germline testing

Existing guidance regarding clinically informed germline testing for patients with cancer is effective for evaluation of classic hereditary cancer syndromes and established gene/cancer type associations. However, current screening methods may miss patients with rare, reduced penetrance, or otherwise occult hereditary risk. Secondary finding of suspected germline variants that may confer inherited cancer risk via tumor comprehensive genomic profiling (CGP) has the potential to help address these limitations. However, reporting practices for secondary finding of germline variants are inconsistent, necessitating solutions for transparent and coherent communication of these potentially important findings. A workflow for improved confidence detection and clear reporting of potential pathogenic germline variants (PPGV) in select cancer susceptibility genes (CSG) was applied to a research dataset from real-world clinical tumor CGP of > 125,000 patients with advanced cancer. The presence and patterns of PPGVs identified across tumor types was assessed with a focus on scenarios in which traditional clinical germline evaluation may have been insufficient to capture genetic risk. PPGVs were identified in 9.7% of tumor CGP cases using tissue- and liquid-based assays across a broad range of cancer types, including in a number of "off-tumor" contexts. Overall, PPGVs were identified in a similar proportion of cancers with National Comprehensive Cancer Network (NCCN) recommendations for germline testing regardless of family history (11%) as in all other cancer types (9%). These findings suggest that tumor CGP can serve as a tool that is complementary to traditional germline genetic evaluation in helping to ascertain inherited susceptibility in patients with advanced cancer.