One of the first medical traumas most newly-diagnosed solid tumor cancer patients struggle with is a biopsy. Many types of biopsies are painful and tricky to get, and sometimes the samples are less than ideal. Some tumors simply can not be biopsied due to their location. But recent advances in genomic sequencing are giving rise to a variety of non-invasive screening and pathology tests. A Silicon Valley company called Guardant now makes an FDA-approved blood test which provides virtually all of the information of a solid tumor biopsy, plus a lot more. The company, and some of it’s proprietary modeling technology, is profiled in yesterday’s USA Today.
Guardant’s test, called Guardant360, became available in February, 2014, and has been used in some of the nation’s top cancer centers. This blood test measures cell-free DNA which is shed by solid tumors into the bloodstream. In doing so, the test is able to sequence DNA from any tumor locations in the patient’s body rather than just a single biopsy area. Guardant reports that, “Recent clinical studies with Guardant360 have shown excellent performance in the top five cancers (breast, lung, colorectal, skin and prostate).” The DNA fragments detected by Guardant’s test are often too small to be detected by other common DNA sequencing technologies. The company says its test enables “high-fidelity, single-molecule DNA sequencing and improves detection sensitivity well over 100-fold.”
Currently, Guardant360 is targeted for use by patients who have been diagnosed with a solid lesion which should be biopsied, or existing cancer patients needing to track their progress for treatment planning. The test results provided by Guardant360, which usually come back to the patient in 2 weeks, not only provides a specific solid tumor diagnosis (if evidence of a tumor is found), but associated treatment options and clinical trials based on the specific genomic alterations detected. Guardant360 does a 68-gene panel of sequencing, including common oncogenes such as EGFR, BRAF, and PTEN. Many tumors alter over time, and understanding how genomic alterations evolve in a specific tumor can help determine treatment options.
But Guardant is careful to say that it’s test does not predict responses to chemo treatments or provide prognosis. In theory, this type of information could, in fact, be determined with tests like Guardant360, but significant research to validate such claims would need to be completed. The use of Guardant360 purely for cancer screening in healthy adults is another area, which at least publicly, has not been discussed by Guardant.
Guardant claims they are currently the only company offering comprehensive genomic cancer testing from a blood sample, but the popularity and accessibility of genomic sequencing is bound to increase as the technology improves. Similar but much more narrow genomic blood tests currently exist for many types of cancer in various stages of development, including brain cancers for which biopsies are more challenging to acquire due to tumor locations.