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Tumor-only genetic sequencing may mislead treatment for cancer patients: study

Xinhua, April 16, 2015 Adjust font size:

Tumor-only genetic sequencing as currently employed by many doctors may misdirect treatment in a large fraction of cancer patients, U.S. researchers said Wednesday.

The findings, published in the U.S. journal Science Translational Medicine, showed that not all genetic changes identified in a cancer are related to the cancer.

Some, the researchers explained, are so-called germline changes, which are inherited changes in genes that are in normal tissues and differ from person to person.

Therefore, doctors should compare the genetic sequence of an individual's tumor and his or her own normal cells in order to know which changes are more likely to be cancer-related and which treatments are likely to work, they said.

"Increasingly, hospitals and companies are beginning to sequence patients' tumors in an attempt to personalize therapy," Victor Velculescu, professor of Johns Hopkins University School of Medicine who led the study, said in a statement.

"However, many are not sequencing each person's normal tissue to filter out non-cancer related changes and to really understand what is occurring in the tumor," Velculescu said.

According to the researchers, inaccurate genetic information can lead to serious side effects from inappropriate therapies, lack of useful targeted therapies and increased costs of patient care from misguided medicines.

For the study, Velculescu and his colleagues compared the genomes of tumor and normal tissue from 815 patients who had a variety of cancers, including breast, brain, renal, gastric, lung, pancreatic, blood cancers and melanoma.

They found that 65 percent of the genetic changes identified with tumor-only genetic sequencing were "false positives" and not related to the patient's cancer.

The researchers also looked at changes in "actionable genes," or genes for which some kind of drug or cancer therapy has already been identified, and found these false positive changes affected nearly one in every two patients analyzed.

"These findings suggest that sequencing paired tumor and normal samples would yield more accurate diagnosis and treatment plans than the current standard methods," Angela Colmone, associate editor at Science Translational Medicine, told reporters.

"Such analysis should become increasingly feasible as the costs of sequencing decrease over time." Endite