Liquid Biopsy Effective in Tracking Changes in Tumors: Study

Cancer detection at the right time is important and keeping track of the changes in tumors for cancer patients is equally important. With effective tracking of changes in the tumor, doctors can fine-tune treatment and can ascertain if the treatment is effective for the patient. Diagnosing cancer and monitoring its progression will likely become less painful and risky in the near future as a blood test to detect cancer mutations has produced results that match those of an invasive tumor biopsy.

Known as liquid biopsies, the blood tests take advantage of the fact that DNA fragments from tumors can be detected in minuscule amounts in the blood of cancer patients.

A tumor biopsy, in which a small piece of the tumor is extracted by surgery, is quite complicated. Moreover, the patient has to suffer pain and endure risk. However, researchers believe that liquid biopsies can become an efficient alternative to conventional and invasive tumor biopsies

Researchers looked at the results of nearly 15,000 liquid biopsies conducted by Silicon Valley start-up Guardant Health and found that a particular mutation found in the blood of cancer patients was also found in the tumor 94 to 100 percent of the time.

However, one shortcoming of the liquid biopsy is that no tumor DNA was detected in the blood of nearly 15 percent of cancer patients. Philip C. Mack, director of molecular pharmacology at the UC Davis Comprehensive Cancer Center, said, “There are simply tumors that do not shed DNA into circulation at detectable levels, so we are bound to miss them.”

Dr. Edward Kim, an expert on lung cancer mutations also said that the results showed the liquid biopsy isn’t accurate and stressed that an actual tumor sample allows a more thorough analysis.

The results were presented at the most recent annual meeting of the American Society of Clinical Oncology.

According to a story published on the topic by Trib Live News, “The findings suggest that liquid biopsies provide an accurate snapshot of the genomic landscape of the tumor,” stated a news release that accompanied the data, which was released Saturday at the annual meeting of the American Society of Clinical Oncology here. The liquid biopsy test used in the study was Guardant360, which looks for almost 70 mutations. It is made by Guardant Health, which also funded the effort.

Liquid biopsies are a hot field, with several companies, including Foundation Health and Grail, either marketing tests or working to develop them. Such tests are designed to pick up in the bloodstream small pieces of DNA shed by cancerous tumors – information that they can be used to treat and monitor the disease. Currently, doctors largely use surgical biopsies for information about a tumor’s genetic mutations and whether cancer can be treated with available drugs. But such biopsies are invasive and can be expensive and painful.

“In the study, the test results were compared with conventional biopsies in two ways. For 398 patients, DNA circulating in the bloodstream was compared with tissue samples previously removed from patients. For the rest of the patients, researchers compared blood test results to those for tissue biopsies in data from large databases,” according to a recent Washington Post report.

Mack and other physicians said that traditional biopsies will remain the “gold standard” because they provide more information on the characteristics of tumors and how they are likely to develop. Mack said a trained pathologist can determine what kind of tumor is presently based on the appearance of cells in a tissue sample – and whether cancer an extracted from the liver actually originated somewhere else, like in the lung.

A report published in NY Times informed, “A blood test to detect cancer mutations produced results that generally agree with those of an invasive tumor biopsy, researchers reported, heralding a time when diagnosing cancer and monitoring its progression may become less painful and risky. The blood tests, known as liquid biopsies, represent one of the hottest trends in oncology. They take advantage of the fact that DNA fragments from tumors can be found in tiny amounts in the blood of patients with cancer.”

Just this week the Food and Drug Administration gave its first approval for such a test, one developed by Roche to detect mutations in a particular gene. Lung cancers with mutations in that gene are vulnerable to treatment with certain drugs, including Roche’s own Tarceva. Many liquid biopsy tests are being sold by other companies under rules that do not require F. D. A. approval.

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