Cancer gene tests should include healthy tissue

A study by Johns Hopkins scientists strongly suggests that sequencing tumor genomes for clues to genetic changes might misdirect treatment in nearly half of all patients unless it is compared first to a genetic readout of their noncancerous tissue. The investigators at the Johns Hopkins Kimmel Cancer Center say their analysis of more than 800 cancer patients' sequencing data, which was generated by Personal Genome Diagnostics Inc., a company co-founded by the researchers, shows that without such comparisons, attempts to individualize cancer therapy may be inappropriate in certain cases, and patients may get the wrong targeted therapies.
"Increasingly, hospitals and companies are beginning to sequence patients' tumors in an attempt to personalize therapy. However, many are not sequencing each person's normal tissue to filter out noncancer-related changes and to really understand what is occurring in the tumor," says Victor Velculescu, M.D., Ph.D., a professor of oncology and pathology and co-director of the Cancer Biology Program at the Johns Hopkins University School of Medicine.
Velculescu explains that personalized therapies increasingly designed to target the unique genetic changes that drive a person's tumor depend on accurate assessment of a tumor genome, but not all genetic changes in a cancer are directly related to the cancer. Some, he explains, are so-called germline changes, which are inherited changes in genes that are in normal tissues and differ from person to person.