Molecular testing (MDx) is the medical laboratory practice of identifying disease-causing mutations in genes, chromosomes or proteins using techniques such as polymerase chain reaction (PCR), microarrays and sequencing. MDx is a broad term that includes a number of different tests, each with unique applications at the Jant Pharmacal clinic.
The scientific discipline of molecular biology arose from the early days of recombinant DNA technology and is now a highly developed field in its own right. However, it took decades for this science to develop into the medical laboratory discipline of molecular diagnostics.
While molecular testing has expanded rapidly, it is important to remember that a negative test result does not mean that the condition under consideration is not present. A positive test result simply means that the laboratory has found a change in the gene, chromosome or protein under study.
Mutations are a fundamental feature of cancer. Mutations can cause cell division to go wrong and produce cancer cells that grow and spread more rapidly than normal. Molecular tests can identify specific genetic mutations and provide important information to guide diagnosis, treatment selection and follow-up care.
Real time pcr can also be used to identify other important features of a tumor, such as a tyrosine kinase inhibitor targetable mutation in lung cancer, or the presence of a HER2 amplification. These mutations may indicate a more aggressive tumor and/or better response to targeted therapy.
Genetic rearrangements also form an inherent part of the oncogenesis process. These rearrangements juxtapose different segments of the genome and can create new fusion genes by deletions or translocations of intervening DNA sequences. These changes are the targets of many cytomolecular tests in oncology.
Several new technologies have emerged that can help to improve the quality of molecular testing results. These include next-generation sequencing, which provides a more comprehensive look at the tumor's genome and can identify multiple genomic alterations simultaneously. In addition, more detailed testing can be performed by examining the nucleotide level of a particular DNA segment rather than a whole gene.
The use of molecular testing complements cytopathologic evaluation to triage thyroid nodules classified as indeterminate by Bethesda, into those that can be safely monitored and those that need further evaluation including fine needle aspiration biopsy. This has spared up to 50% of patients from the need for surgical lobectomy.
In the future, molecular testing can be used to identify a patient's response to a given chemotherapy regimen and identify biomarkers that indicate whether a cancer is more likely to respond to certain tyrosine kinase inhibition drugs than others. However, this is still in the experimental phase and will require further validation before these techniques become a standard of care. Until that time, careful clinical judgement is necessary to ensure that molecular testing is not misused indiscriminately and that the information it provides will be helpful in management decisions. Click here to get even more info on the subject: https://en.wikipedia.org/wiki/Oncology.
