Introduction: We evaluated germline and somatic testing practices and compared results from tissue and liquid biopsy specimens in a large community urology setting.
Methods: A retrospective analysis was performed on advanced prostate cancer patients from a single community practice between June 2016 and September 2021. Clinical data and sequencing results from tissue and liquid biopsy specimens were available for 389 patients. Genomic data were available for 81 tissues and 74 liquid biopsy specimens. Comparison of genomic findings included 81 tissues and 27 liquid biopsy specimens. The number of actionable biomarkers and patients screened and enrolled in clinical trials was assessed from germline and somatic testing. Frequency of pathogenically altered genes, alteration types, and biomarkers were assessed from tissue and liquid specimens. Alteration frequency was compared between specimen types for the top 25 altered genes.
Results: Clinically relevant alterations were found from germline and somatic testing in both tissue and liquid biopsy specimens. The frequency of microsatellite instability-high, tumor mutational burden-high, or alterations in homologous recombination repair genes was consistent with published findings. Concordance between tissue and liquid findings varied with low circulating tumor DNA.
Conclusions: Germline and somatic testing is critical for treatment decisions and should be standard of care for community practices. Liquid biopsy is a viable alternative when circulating tumor DNA is high.
Keywords: castration-resistant; circulating tumor DNA; liquid biopsy; microsatellite instability; poly(ADP-ribose) polymerase inhibitors; prostatic neoplasms.