3.6 Circulating Tumor DNA
Figure 3 shows change in ctDNA levels over time for patients with osteosarcoma (panel A ) and Ewing sarcoma (panelB ). All four patients with osteosarcoma and available baseline samples had detectable ctDNA >10% (median 16.9%, range 12.4% – 35.5%). Levels decreased during therapy in two osteosarcoma patients and increased during therapy in the other two patients. Of these two patients, one had stable disease at re-evaluation and one was not able to be re-evaluated. A fifth patient without a baseline sample had detectable ctDNA at cycle 1 day 3 that subsequently decreased during therapy. ctDNA was detectable in 5/7 patients with Ewing sarcoma, with a median percent ctDNA level of 2.11 (range 0.31 – 54.08) among those 5 patients. Of the five patients with detectable ctDNA at baseline, levels increased in one patient with clinical progression. In the other four patients, levels either decreased and remained low throughout therapy or were low at baseline and remained low throughout therapy. The sole patient with Ewing sarcoma who had a partial response did not have detectable ctDNA at baseline or during therapy.