New large-scale study shows that blood tests can be used to diagnose cancer.
A large-scale genomic analysis finds that patterns of genetic changes detected in blood samples (liquid biopsy) closely mirror those identified in traditional tumor biopsy. With blood samples from more than 15,000 patients and 50 different tumor types, this is one of the largest cancer genomics studies ever conducted.
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This study included 15,191 patients with advanced lung cancer (37%), breast cancer (14%), colorectal cancer (10%), and other cancers (39%). Each patient provided one or more blood samples for analysis of ctDNA.
This study assessed the accuracy of liquid biopsies, as compared to tumor samples, in two ways. First, it compared the patterns of genomic changes in ctDNA to those found in 398 patients with available results of genetic testing of the tumor tissue. When ctDNA was positive for key abnormalities in EGFR, BRAF, KRAS, ALK, RET, and ROS1 that drive tumor growth, the same mutations were reported in tissue 94-100% of the time. Most ctDNA alterations were found at very low levels. Half occurred at a frequency below 0.4% of the total DNA in circulation. The accuracy of the liquid biopsy assay remained high even at these low levels.
“The fact that genomic mutations vary not only patient to patient but also change over time has been a constant challenge in cancer treatment, especially in the precision medicine era,” said Sumanta Kumar Pal, MD, ASCO expert in developmental therapeutics. “Having a good, reliable option beyond a tumor biopsy could have a major impact on our ability to select the right therapy for the right patient.”
Although ctDNA mutations were detected in 83% of the blood samples in this study, not all patients had sufficient ctDNA for the test. For example, the researchers found that the ability to detect ctDNA is lower for patients with glioblastoma, presumably because the blood-brain barrier makes it more difficult for ctDNA from a brain tumor to enter the circulation.
They are addressing this by increasing the sensitivity of the assay to detect mutations at extremely low levels of ctDNA, which will not only make the test more sensitive for all solid cancer types in advanced stages, but also in applying this technology to cancers in earlier stages.
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The study has been presented at the 2016 American Society of Clinical Oncology (ASCO) Annual Meeting. The full abstract is available here.