In patients with high disease burden, the use of cfDNA for genetic profiling when biopsy is unavailable may be feasible. Our results support further investigations into the clinical utility of cfDNA in a larger cohort of patients.

The molecular scenario of breast cancer has become more complex in the last few years. Distinguishing between BRCA-associated, sporadic, HER2-enriched and triple-negative tumors is not sufficient to allow effective clinical management. Basal-like breast cancer, a subtype of triple-negative breast cancer, differs from others grouped under this heading. Commonalities between BRCA-related tumors and basal-like breast cancers (BRCAness phenotype) are highly relevant to ongoing clinical trials, in particular those investigating targeted therapies (e.g. PARP inhibitors) in sporadic breast tumors. The 'gold standard' to identify basal-like phenotype is DNA microarray, but integrated results could provide a panel of biomarkers helpful in identifying 'BRCAness' tumors (e.g. copy number aberrations, abnormal protein localization and altered transcriptional levels) and other molecular targets, such as APE1,the inhibition of which is emerging as an attractive breast cancer treatment in certain therapeutic settings.

Commercially available targeted panels miss genomic regions frequently altered in hepatocellular carcinoma (HCC). We sought to design and benchmark a sequencing assay for genomic screening of HCC. We designed an AmpliSeq custom panel targeting all exons of 33 protein-coding and two long noncoding RNA genes frequently mutated in HCC, TERT promoter, and nine genes with frequent copy number alterations. By using this panel, the profiling of DNA from fresh-frozen (n = 10, 1495×) and/or formalin-fixed, paraffin-embedded (FFPE) tumors with low-input DNA (n = 36, 530×) from 39 HCCs identified at least one somatic mutation in 90% of the cases. Median of 2.5 (range, 0 to 74) and 3 (range, 0 to 76) mutations were identified in fresh-frozen and FFPE tumors, respectively. Benchmarked against the mutations identified from Illumina whole-exome sequencing (WES) of the corresponding fresh-frozen tumors (105×), 98% (61 of 62) and 100% (104 of 104) of the mutations from WES were detected in the 10 fresh-frozen tumors and the 36 FFPE tumors, respectively, using the HCC panel. In addition, 18 and 70 somatic mutations in coding and noncoding genes, respectively, not found by WES were identified by using our HCC panel. Copy number alterations between WES and our HCC panel showed an overall concordance of 86%. In conclusion, we established a cost-effective assay for the detection of genomic alterations in HCC.

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Improved survival rates for prostate cancer through more effective therapies have also led to an increase in the diagnosis of metastases to infrequent locations such as the brain. Here we investigate the repertoire of somatic genetic alterations present in brain metastases from 51 patients with prostate cancer brain metastases (PCBM). We highlight the clonal evolution occurring in PCBM and demonstrate an increased mutational burden, concomitant with an enrichment of the homologous recombination deficiency mutational signature in PCBM compared to non-brain metastases. Focusing on known pathogenic alterations within homologous recombination repair genes, we find 10 patients (19.6%) fulfilling the inclusion criteria used in the PROfound clinical trial, which assessed the efficacy of PARP inhibitors (PARPi) in homologous recombination deficient prostate cancer. Eight (15.7%) patients show biallelic loss of one of the 15 genes included in the trial, while 5 patients (9.8%) harbor pathogenic alterations in BRCA1/2 specifically. Uncovering these molecular features of PCBM may have therapeutic implications, suggesting the need of clinical trial enrollment of PCBM patients when evaluating potential benefit from PARPi.