Diagnostic – the investigative tools and techniques used in biological studies or to identify or determine the presence of a disease or other condition.

Epidermal growth factor receptor (EGFR) – a receptor that is overproduced in several solid tumors, including breast and lung cancers. Its overproduction is linked to a poorer prognosis because it enables cell proliferation, migration, and the development of blood vessels. Several new drugs recently approved by the Food and Drug Administration specifically target EGFR.

Genomics – the study of all of the nucleotide sequences, including structural genes, regulatory sequences, and noncoding DNA segments, in the chromosomes of an organism or tissue sample. One example of the application of genomics in oncology is the use of microarray or other techniques to uncover the genetic “fingerprint” of a tissue sample. This genetic fingerprint is the pattern that stems from the variable expression of different genes in normal and cancer tissues.

Herceptin – see Human epidermal growth factor receptor 2.

Human epidermal growth factor receptor 2 (HER2) – a growth factor receptor that is used as a breast cancer biomarker for prognosis and treatment with the drug trastuzumab (Herceptin), which targets the HER2 protein. The HER2 protein is overexpressed in approximately 25 percent of breast cancer patients due to amplification of the gene.

Laboratory-Developed Tests – in this report, laboratory-developed tests include tests that are predictive of a therapeutic response that have not gone through the FDA approval process. The laboratories that provide these tests are, however, subject to oversight by CMS under CLIA.

Off-label use – using a drug that either has not been approved by the Food and Drug Administration or has not been approved for the purpose for which it is being used.

Phase I trial – clinical trial in a small number of patients in which the toxicity and dosing of an intervention are assessed.