Many of the mutations that are found with tumor-only genetic sequencing are not actually tumor-related. Instead, they are just germline mutations, which are inherited changes that differ from person to person. They are common in normal tissues, and they are not necessarily related to cancer.
Tumor-only genetic sequencing, then, may lead personalized cancer therapies astray—unless genomic information from a patient’s tumor is compared with genomic information from the patient’s normal tissue. Without this check, innocuous genetic changes may be thought “actionable” and therapies thought “targeted” may stray wide of the mark.
Essentially, the problem is a failure to distinguish between positive results and false-positive results. The scale of the problem, warn scientists from Johns Hopkins University and Personal Genome Diagnostics, is considerable.
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