Clonal evolution of low-burden TP53 mutations in patients treated with first-line chemo- and/or immunotherapy. All patients analyzed in relapse and 3 patients with a TP53 mutation expanded in remission with no relapse sample available were included (n = 55; supplemental Figure 9). Mutation with the highest VAF was considered in each case, irrespective of whether it was the same mutation as in a pretreatment sample (for details, see supplemental Table 9). (A) Mutation burden before therapy and during relapse in patients with low-burden TP53 mutations. Dashed line, 10% VAF threshold. For cumulative VAF see supplemental Figure 10B. (B) Estimated fraction of TP53-mutated (TP53-mut) (red line) and TP53-wt cells (green line) before therapy, during remission and after TP53-mut/cnLOH expansion in relapse in patient 1507. Bars, NGS result (right y-axis). (C) Number of mutations before therapy and during relapse. Before treatment: multiple mutations in 18 of 82 (22%) patients, median 1 mutation per patient (range, 1-27); relapse: multiple mutations in 31 of 53 (58%) patients, median 2 mutations per patient (range, 1-48). Red line, median. (D) Proportion of patients, in whom the TP53 mutation exceeded 10% VAF threshold in relapse stratified according to pretherapy subclone size. In total, during median follow-up of 4.1 years (range, 1.3-11.6; median number of therapy lines 2, range 1-3) we observed that the TP53-mut subclone expanded above the 10% VAF threshold in 29 patients.