The molecular level of a patient’s tumor
Some cancers are caused by specific changes to genes and genomic testing can help identify these alterations and give doctors a better idea of how to treat a patient. Studies show that 30-49% of patients who undergo genomic testing have alterations that can then be matched to a specific treatment that could benefit them1.
Identifying TRK fusion cancer through genomic testing
An example of a type of cancer that can best be identified through comprehensive genomic testing is TRK fusion cancer.
Different types of tests are available today that can help detect TRK fusion cancer
- Next-generation sequencing (NGS)
This method provides a detailed view of a large number of genes and can identify NTRK gene fusions among other gene alterations. It is the most comprehensive method.
- Immunohistochemistry (IHC)
This test does not look at changes in the genes, but what the gene produces: altered proteins. IHC is a lab test uses antibodies to test for certain antigens (markers) in a sample of tissue – in this case it can detect TRK fusion proteins. The antibodies are usually linked to an enzyme or a fluorescent dye. When the antibodies bind to the antigen in the tissue sample, the enzyme or dye can be activated, and the antigen could then be seen under a microscope. Confirmation of NTRK gene fusion by an additional method is needed after a positive IHC test for TRK fusion cancer.8
- Fluorescence in situ hybridization (FISH)
A laboratory technique used to look at genes or chromosomes in cells and tissues. Pieces of DNA that contain a fluorescent dye are made in the laboratory and added to cells or tissues on a glass slide. When these pieces of DNA bind to specific genes or areas of chromosomes on the slide, they light up when viewed under a microscope with a special light9.
- Reverse-transcription polymerase chain reaction (RT-PCR)
A laboratory method used to make many copies of a specific genetic sequence for analysis or other studies. It uses an enzyme called reverse transcriptase to change a specific piece of RNA into DNA, which can be amplified (made in large numbers) by another enzyme called DNA polymerase. RT-PCR may be used to look for certain changes in a gene or chromosome, which may help diagnose a disease, such as cancer11.
1 Massard C, Michiels S, Ferte C, et al. High-throughput genomics and clinical outcome in hard-to-treat advanced cancers: results of the MOSCATO 01 trial. Cancer Discovery 2017;7(6):586-595
2 Stransky N, Cerami E, Schalm S, Kim JL, Lengauer C. The landscape of kinase fusions in cancer. Nat Commun.
3 Vaishnavi A, Le AT, Doebele RC. Cancer Discovery 2015;5(1):25-34.
4 Kumar-Sinha C, Kalyana-Sundaram S, Chinnaiyan AM. Landscape of gene fusions in epithelial cancers: seq and ye shall find. Genome Med.
5 Okimoto RA, Bivona TG. Tracking down response and resistance to TRK inhibitors. Cancer Discovery 2016;6(1):14-16.
6 National Cancer Institute, NCI Dictionary of Cancer Terms: Antibody; Last accessed December 2018
7 National Cancer Institute, NCI Dictionary of Cancer Terms: Antigen; Last accessed December 2018
8 National Cancer Institute, NCI Dictionary of Cancer Terms: Immunohistochemistry; Last accessed December 2018
9 National Cancer Institute, NCI Dictionary of Cancer Terms: In-situ Hybridization; Last accessed December 2018
10 National Cancer Institute, NCI Dictionary of Cancer Terms: RNA; Last accessed December 2018
11 National Cancer Institute, NCI Dictionary of Cancer Terms: RT-PCR; Last accessed December 2018