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Blood Test as Good as Biopsy to Detect Cancer Targets

Detect cancer scrabble

(Marco Verch, Flickr)

28 Feb. 2019. Results of a clinical trial show a commercial blood test works at least as well as tissue biopsies for determining precise genetic mutations causing most lung cancers. Findings from the trial are scheduled for presentation at the annual meeting of American Association for Cancer Research, on 2 April in Atlanta.

Researchers led by thoracic and head-and-neck cancer specialist Vassiliki Papadimitrakopoulou at M.D. Anderson Cancer Center, part of the University of Texas system in Houston, are seeking better methods for identifying underlying molecular causes of solid tumor cancers, in this case non-small cell lung cancer. In many, if not most cases, cancer specialists and pathologists take samples of the tumor tissue with biopsies, invasive surgical procedures, which they analyze to determine the tumor’s precise molecular composition.

Papadimitrakopoulou and colleagues at MD Anderson and 6 other medical centers want to find out if so-called liquid biopsies that analyze blood samples for tumor cells circulating in the blood can detect these characteristic genetic identifiers as well as tissue biopsies. The team evaluated Guardant 360, a commercial liquid biopsy offered by Guardant Health in Redwood City, California to help determine the optimum cancer treatment for individual patients. Guardant 360, tests for 73 genes representing exons, or coding regions for proteins, most associated with cancer-causing mutations for individuals with cancer in advanced stages.

The clinical trial enrolled 282 individuals with non-small cell lung cancer, a group of lung tumors with similar treatments and outlooks, affecting 80 to 85 percent of people with lung cancer, according to American Cancer Society. MD Anderson says the 5-year survival rate for people with non-small cell lung cancer, or NSCLC, is 19 percent.

Participants in the trial received standard tissue biopsies, but also gave blood samples for Guardant 360 testing. The Guardant 360 tests look for 7 known predictive biomarkers for non-small cell lung cancer: ROS1, BRAF, RET, MET, ALK, EGFR and ERBB2. The results show Guardant 360 revealed at least one of these indicators in 77 participants, while tissue biopsies detected at least one biomarker in only 60 participants.

Guardant 360 also looks for KRAS mutations, a prognosis indicator for this kind of cancer, and found this biomarker in 90, or 48 percent, of the 193 remaining trial participants. Tissue biopsies revealed KRAS mutations in only 24 participants. In addition, the results show faster turnaround for liquid biopsies that take 9 days, compared to 15 days tissue testing.

Cancer therapies addressing 4 of the 7 mutations revealed by Gardant 360 — EGFR, ALK, ROS1, and BRAF — are already approved by FDA, which makes this granular level of testing increasingly more important, say the researchers. “When choosing therapy for patients with NSCLC, it is vital that we know which patients have gene mutations that often respond to molecular therapies,” says Papadimitrakopoulou in an MD Anderson statement. “The response rates can be up to 30 percent higher than with chemotherapy or immunotherapy.”

“Given that advanced NSCLC is often fatal, it is important we get patients on treatment at the earliest possible time,” adds Papadimitrakopoulou. “Our findings show that we can greatly reduce the amount of time between testing and initiation of therapy.”

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