Variant allele fraction of genomic alterations in circulating tumor DNA (%ctDNA) correlates with SUVmax in PET scan.

The relationship between higher variant allele fraction (VAF) of genomic alterations in circulating tumor DNA (%ctDNA), an indicator of poor outcome, and maximum standardized uptake value (SUV_max), the most commonly used semi-quantitative parameter in ¹⁸F-FDG PET/CT, has not been studied. Overall, 433 cancer patients had blood-based next generation sequencing. Maximum and sum of %ctDNA alterations (%ctDNA_max and %ctDNA_sum, respectively) represent the maximum and sum of VAF, reported as a percentage. The subset of 46 eligible patients had treatment-naïve metastatic disease and PET/CT imaging, with median 13 days prior to ctDNA testing. We found a linear correlation between the maximum VAF (%ctDNA_max) (as well as the sum of the VAFs (%ctDNA_sum)) and SUV_max of the most ¹⁸F-FDG-avid lesion (r=0.43, P=0.003; r=0.43, P=0.002; respectively). Our data suggest that SUV_max may be a non-invasive and readily available surrogate indicator for %ctDNA, a prognostic factor for patient survival. Since higher %ctDNA has been previously correlated with worse outcome, the relationship between SUV_max, %ctDNA and survival warrants further study.