Genotyping, sometimes referred to as molecular fingerprinting, must be distinguished from genetic testing. Genotyping is done to tumor samples and tests genes in the malignancy only.
Genotyping, sometimes referred to as molecular fingerprinting, must be distinguished from genetic testing. Genotyping is done to tumor samples and tests genes in the malignancy only. There are no implications for children or siblings of patients, whereas genetic testing focuses on inherited conditions and targets people with a worrisome family history.
Michele Myers, BSN, RN, OCN
Michele Myers, BSN, RN, OCN, a thoracic oncology research nurse at the Massachusetts General Hospital Cancer Center, Boston, discussed these topics during her presentation, “Genotype-Directed Therapies For Lung Cancer in 2012,” at Scripps Cancer Center’s 32nd annual Oncology Nurses Symposium, October 7–10, in San Diego.
The science of genotyping has emanated from progress made in the evolution of targeted therapies. Unlike the historical norm of “one treatment fits all” that is based on the cell line or cell type from which cancer cells evolve, genotyping allows for the identification of specific treatment algorithms dependent upon the presence of genetic mutations. In non–small-cell lung cancer, more than 50% of patients have an identifiable genetic abnormality that can be more effectively treated with “smart drugs” than with historical antineoplastic agents. Patients most likely to have the genetic mutations that are amenable to these newer classifications of targeted therapies are those who are lifelong nonsmokers.
While each research institution has its own requirements to pursue genetic testing, Massachusetts General Cancer Center needs a core biopsy of tissue , as well as 15 unstained slides for the purposes of genetic testing. Pathologic results may take 2 to 4 weeks for their determination. A positive genetic mutation finding then dictates the targeted therapy of choice. For example, erlotinib (Tarceva) would be indicated for a positive EGFR mutation. Crizotinib (Xalkori) is the drug of choice for a positive EML4-ALK mutation. Gefitinib (Iressa) is prescribed when EGFR mutations are found.
While the science of genotyping is relatively new, it has enormous potential in customizing therapies for a wide range of malignancies. A host of clinical trials are underway to broaden our understanding of matching targeted therapies with genetic abnormalities.