Using serial testing to detect the emergence of genes underlying tumor resistance to EGFR-targeted therapies would be much simpler using peripheral blood draws than repeated tissue biopsy. 

But clinicians should resist the temptation to “default to the easier, more convenient choice,” Dr Kim cautioned. 


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“I don’t think that’s what we should be doing,” he said. “We still have to try hard to get tumor tissue. And only in those extenuating circumstances when we can’t, should we default to liquid biopsy.”

Tissue biopsy remains the gold standard, Dr Kim emphasized. 

“We can rely on tissue results with a high degree of certainty, whether they are positive or negative,” he explained. “We utilize liquid biopsy up front in the appropriate population of patients with whom we have difficulty obtaining tissue and we will also utilize it as a monitoring [among patients in clinical trials] during treatment and at tumor progression.”

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However, while positive results are accurate more than 90% of the time with liquid biopsy gene panels, negative results are accurate only 74% of the time, Dr Kim told Cancer Therapy Advisor

“That’s why we don’t have as much confidence in negative results when we get them [with liquid biopsy],” he said. “And that is why the recommendation is to redo [the biopsy] after a negative result. It is similar to a PET scan — it’s difficult to believe a negative result but you can be very confident in a positive result.”

Results from large comprehensive genomic tissue testing typically require 2 to 3 weeks, he noted, whereas the smaller gene panels used with liquid biopsy should be faster to process.

“In my dream scenario I think it would be wonderful to have blood and tissue done at the same time,” Dr Kim said. “You’d get a preliminary read from the blood early on, in less than 2 weeks, and then the larger panel later on, for validation. It would allow the clinician to make a determination or estimate about what types of treatment we should be considering. I would hope that down the road blood will become just as accurate but more convenient.”

References

  1. Rolfo C, Mack PC, Scagliotti GV, et al. IASLC statement paper: liquid biopsy for advanced non-small cell lung cancer (NSCLC)[published online June 6, 2018]. J Thorac Oncoldoi: 10.1016/j.jtho.2018.05.030
  2. International Association for the Study of Lung Cancer. ASLC issues statement paper on liquid biopsy for lung cancer [press release]. https://www.iaslc.org/news/iaslc-issues-statement-paper-liquid-biopsy-lung-cancer. Published June 20, 2018. Accessed July 20, 2018.