Table S1. Numeric Demographics and Biomarker Status Variables of the Studied LGG Population

Variable N Median Mean SD IQR #NA Observed data Age 210 40.5 41.9 13.2 16.4 0 Tumor volume 51 71.3 92.9 72.6 104.6 159 MGMT met 136 60.0 48.3 37.9 81.9 74 TP53 ihc 145 1.0 10.6 15.6 20.0 65 Imputed data Age 10500 40.5 41.9 13.2 16.5 0 Tumor volume 10500 112.2 118.9 82.6 175.3 0 MGMT met 10500 53.0 46.6 38.1 81. 0 1 TP53 ihc 10500 1.0 11.7 16.1 30.0 0

Table S1. Numeric demographics and biomarker status variables of the studied LGG population. The number of observations (N), the median, the mean, the standard deviation (SD), the interquartile range (IQR) and the number of missing values (#NA) are shown. Top: observed data; bottom: imputed data. The total number of 10500 observations in the lower part of the table results from multiplying the number of patients in the dataset (210) by the number of imputations (50). Variable Levels Observed data Imputed data N % N % Gender female 84 40.0 4200 40.0 male 126 60.0 6300 60.0 total 210 100 10500 100 missing 0 LGG histology A II 92 44.2 4672 44.5 OA II 63 30.3 3161 30.1 OG II 53 25.5 2667 25.4 total 208 100 10500 100 missing 2 WHO grading after MT III 45 81.8 2558 74.1 IV 10 18.2 892 25.9 total 55 100 3450 100 missing 155 IDH status IDHwt 35 16.7 2060 19.6 IDHmut 150 71.4 8440 80.4 unknown 25 11.9 total 210 100 10500 100 MGMT status MGMTunm 41 30.1 3416 32.5 MGMTmet 95 69.8 7084 67.5 total 136 100 10500 100 missing 74 TP53 status TP53neg 110 75.9 7579 72.2 TP53pos 35 24.1 2921 27.8 total 145 100 10500 100 missing 65 1p19q status 1p19qret 121 75.6 8099 77.1 1p19qloh 39 24.4 2401 22.9 total 160 100 10500 100 missing 50 Molecular stratification IDHwt 35 33.3 2060 19.6 IDHmut, 21 20.0 2630 25.1 MGMTmet IDHmut, 14 13.3 1731 16.5 MGMTmet, TP53pos IDHmut, 26 24.8 2141 20.4 MGMTmet, 1p19qloh other 9 8.6 1938 18.5 total 105 100 10500 100 missing 105 Epilepsy no 40 23.1 2497 23.8 yes 133 76.9 8003 76.2 total 173 100 10500 100 missing 37 Neurodeficits no 108 70.1 7309 69.6 yes 46 29.9 3191 30.4 total 154 100 10500 100 missing 56

Table S2. Categorial demographics and biomarker status variables of the studied population. Numbers and percentages are shown. Left: observed data; right: imputed data. IDH status Death overall Observed MT Death without MT Death after MT IDHwt 1771 N/A N/A 372 IDHmut 4048 4140 N/A 1218 Unknown 2155 N/A 2415 1630

Table S3. Median times to event in days by IDH status. N/A: not applicable, i.e. when <50% of patients experienced the event. The shorter median time to death overall than to observed MT for IDHmut patients is due to the mixture of deaths without MT and deaths after MT which are comprised by death overall.