Key Points
• In the current prospective study, researchers assessed a sample of 40 patients in which one driver mutation in ctDNA (EGFR, KRAS or BRAF) was detected, with a minimum of three follow-up blood samples drawn. The authors assessed radiographic response to therapy via CT, thus categorizing as partial response (PR), stable disease (SD) or progressive disease (PD) per RECIST.
• The investigators suggested that serial testing of ctDNA could complement radiographic therapy response monitoring. It could also direct the imaging frequency in the setting of lung cancer. Furthermore, ctDNA and Cyfra21-1 are relevant biomarkers for therapy response monitoring, with Ca125 also potentially proving useful.
• Although ctDNA would be the best biomarker to follow therapy response, not all patients exhibit a detectable driver mutation at baseline, thus Cyfra21-1 and perhaps CA125 could monitor disease progression instead.
• According to the authors, “In the present study, only patients with a detected ctDNA mutation at baseline and an elevated serum protein biomarker are discussed. However, hypothetically, the ctDNA concentration can increase from undetectable to a detectable level or the protein concentration could increase from a normal to an abnormal level, indicating PD [progressive disease]. Therefore, if at baseline a driver mutation is not detectable in liquid biopsy, but only in tumor tissue, it could still be relevant to monitor the specific driver mutation in liquid biopsies. In addition, although we did not find any significant associations between protein markers with a normal baseline concentration and therapy response, it could yet be useful to monitor all protein biomarkers.”