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Table 1. Select Definitions of Commonly Used Terms in
Precision Oncology
Term Definition
Biomarker A biological marker that can be detected and measured by a
validated test to diagnose or treat disease, including genes,
genomic alterations, ribonucleic acid (RNA) transcripts,
proteins, post-translationally modified forms of proteins, and
signatures of combinations of the aforementioned biomarkers.
Circulating tumor
DNA (ctDNA)
Tumor deoxyribonucleic acid (DNA) shed into the plasma.
Clonal Tumor cells derived from the division of a common ancestral
tumor cell.
Copy number
variation (CNV)
Deviation from the expected two copies of a gene within a cell.
• Amplification: An increase in the number of gene copies
within a cell beyond the expected two copies. Amplifications
may be focal and limited to a specific gene or part of a broader,
typically lower level, chromosomal gain.
• Deletion: A decrease in the number of copies of a gene due to
the loss of a single copy (heterozygous deletion) or both copies
(homozygous deletion).
Fusion A novel gene product that is created from two previously
separate and independent genes.
Genomic alteration Alteration of a gene from its original wildtype (normal) status
through mutation, CNV, or rearrangement.
Genomic instability A high frequency of mutations within the tumor's genome, which
may be caused by loss of expression or function of proteins that
direct DNA repair and/or are involved in mitotic checkpoints.
Genomic instability
score (GIS)
A measurement of genomic instability that reflects homologous
recombination deficiency.
The companion diagnostic for niraparib utilizes a GIS, which
measures the presence of telomeric allelic imbalance (TAI), loss
of heterozygosity (LOH), and large-scale state transitions (LST)
i.e., large structural variants.
Genomic
biomarker-linked
therapy
Therapy selected to target specific genomic alterations detected
within the tumor. This includes targeted therapy designed
to inhibit gain-of-function mutations in oncogenes, loss-of-
function mutations in tumor suppressors, or other pathways
sensitive to specific therapies due to the presence of a genomic
alteration.
Germline Mutations (variants) that are present within the egg and sperm
that united to form the zygote from which an individual
develops and are thus heritable. Inherited germline mutations are
present within both tumor and normal samples sequenced.
