ctDNA datawere available for 14 evaluable pts; 13 in which somatic alterations were detected. ctDNA analysis detected NTRK gene fusions in 46% of the pts at treatment start. Bythe data cut-off, 6 pts had a progression event with ctDNA data available for 5 pts. Potential acquired mutations were identified in 3 pts: one with NTRK1 F589L and G595R, one with SMAD4 R361C and the third with ARID1A K1238fs and FGFR2 R210Q mutations.