Genetic Testing in Cancer-Stage & Treat

Time October 19, 2020 pp25 |The Brief Health|”Why doctors are turning to the blood to learn more about tumors” by Alice Park

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Summary of Article

Newer cancer-tests are becoming routine . “These tests pick up genetic material shed by cancer tumors into the blood, which lets doctors avoid the invasive procedures they traditionally use to extract sample directly from tumors.” These genetic signatures “can provide genetic clues about the mutations that are driving the tumors and can direct doctors to the best drugs for treating them.” Most of the newer FDA-approved tests are called “Companion Diagnostics” because they are developed in tandem with drugs that target specific cancer pathways. Companies at the forefront are: Guardant Health-“tracks 55 genetic mutations in any solid cancer” and is tied to treatment with Osimertinib, and Foundation Medicine-analyzes 3000 cancer-related genes. Sampling blood, for these genetic markers, has the potential to provide information on tumors that are otherwise difficult to biopsy. Blood-based “biopsies” may also provide a more comprehensive look at the tumor activity. This presumes that all markers are shed in the blood and are at detectable levels. Traditional surgical biopsies or needle biopsies provide unique information, that will remain important, but they are limited by the process of taking a sample. In contrast, one can think of blood biopsy as more akin to capturing the entire population of genetic markers for cancers.

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Although screening for cancer, using traditional tumor markers, has not been successful or advised these newer molecular-based techniques may be better at discriminating cancer from normal tissue because the cancer genes, unlike common tumor markers, aren’t expressed by normal cells. Although, a way off from becoming reality having such a capability to effectively screen blood for cancer will allow earliest intervention. Besides Guardant Health and Foundation Medicine, “Grail, a spin-off of Illumina…is focusing its efforts on exactly this; in March, it published data from thousands of patients showing that its test can pick up 50 different cancers.”

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