Quote:"the most important findings of our study are that early changes in ctDNA are associated with later tumor responses as assessed by imaging, and that serial ctDNA measurement has significant potential to complement standard RECIST-based disease assessment.... Serial ctDNA analysis should be incorporated into future clinical trials to provide a more robust assessment of this promising biomarker.
As we've seen, changes in ctDNA can be observed within day after starting effective therapy. The physical mass of a tumor requires time to die off -- so visible tumor shrinkage on imaging can then be observed within 6 to 12 weeks.
ctDNA -- fast. ORR -- later.