Impact of Simultaneous Circulating Tumor DNA and Tissue Genotyping in the Workup of Stage IV Lung Adenocarcinoma on Quality of Care in an Academic Community Medical Center.

Purpose: In patients with metastatic lung adenocarcinoma, evidence-based first-line treatment decisions require analysis of tumors for genomic alterations (GAs). Optimizing the genotyping paradigm may improve the delivery of precision oncology care. Actionable GAs can be identified by analyzing tumor tissue or circulating tumor DNA using liquid biopsy. Consensus guidelines for when to use liquid biopsy have not been established. We evaluated the routine use of liquid biopsy performed with tissue testing in patients with newly diagnosed, stage IV lung adenocarcinoma.

Methods: We performed a retrospective study comparing patients who underwent tissue genotyping alone (standard biopsy group) with patients who had simultaneous liquid and tissue genotyping (combined biopsy group). We examined the time to reach a final diagnosis, the need for repeat biopsies, and diagnostic accuracy.

Results: Forty two patients in the combined biopsy group and 78 in the standard biopsy group met the inclusion criteria. The standard group had a mean time to diagnosis of 33.5 days, compared with 20.6 days in the combined group ( < .001 by two-tailed -test). In the combined group, 14 patients did not have sufficient tissue for molecular analysis (30%); however, in 11 (79%) of these patients, liquid biopsy identified a GA that eliminated the need for a second tissue biopsy. In patients who completed both tests, each test found actionable GAs missed by the other.

Conclusion: Performing liquid biopsy simultaneously with tissue genotyping is feasible in an academic community medical center. Potential advantages of simultaneous liquid and tissue biopsies include shorter time to obtain a definitive molecular diagnosis, reduced need for a repeat biopsy, and improved detection of actionable mutations, although a sequential strategy that saves costs by beginning with a liquid biopsy may be ideal.